Tasmia Zaman, Yue Jiang, Sajjad Seifi Mofarah, Saroj Kumar Bhattacharyya, Pramod Koshy, John E. Daniels, Charles Christopher Sorrell
The system BaO–TiO2 is technically important because it contains multiple dielectric and ferroelectric phases, including the important BaTiO3, which is one of the most widely studied dielectric perovskites owing to its dual piezoelectric and ferroelectric properties. The present work revises the subsolidus phase equilibria data by synthesizing previous phase equilibria data and new experimental results using high‐temperature (600°–1300°C) and long‐term (≤336 h) equilibration, coupled with analytical work based principally on room‐temperature X‐ray diffraction. The resultant phase diagram is given in both mole and weight percents, extending from the liquidus surface (not investigated) to absolute zero temperature (for inclusion of the previously excluded crystallographic and ferroelectric phase transformations). The major features include (1) correction of four eutectoid and three peritectoid reactions and corresponding temperatures, (2) indication of inferred partial solid solubilities, (3) clarification of the BaTiO3 solid solubility homogeneity regions, and (4) specification of some invariant point compositions on the liquidus surface.
{"title":"Phase equilibria in the system BaO–TiO2","authors":"Tasmia Zaman, Yue Jiang, Sajjad Seifi Mofarah, Saroj Kumar Bhattacharyya, Pramod Koshy, John E. Daniels, Charles Christopher Sorrell","doi":"10.1111/jace.20143","DOIUrl":"https://doi.org/10.1111/jace.20143","url":null,"abstract":"The system BaO–TiO<jats:sub>2</jats:sub> is technically important because it contains multiple dielectric and ferroelectric phases, including the important BaTiO<jats:sub>3</jats:sub>, which is one of the most widely studied dielectric perovskites owing to its dual piezoelectric and ferroelectric properties. The present work revises the subsolidus phase equilibria data by synthesizing previous phase equilibria data and new experimental results using high‐temperature (600°–1300°C) and long‐term (≤336 h) equilibration, coupled with analytical work based principally on room‐temperature X‐ray diffraction. The resultant phase diagram is given in both mole and weight percents, extending from the liquidus surface (not investigated) to absolute zero temperature (for inclusion of the previously excluded crystallographic and ferroelectric phase transformations). The major features include (1) correction of four eutectoid and three peritectoid reactions and corresponding temperatures, (2) indication of inferred partial solid solubilities, (3) clarification of the BaTiO<jats:sub>3</jats:sub> solid solubility homogeneity regions, and (4) specification of some invariant point compositions on the liquidus surface.","PeriodicalId":200,"journal":{"name":"Journal of the American Ceramic Society","volume":null,"pages":null},"PeriodicalIF":3.9,"publicationDate":"2024-09-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142257196","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Boron nitride (BN) powders with near‐spherical particles of more than 10 µm were synthesized by templated carbothermal reduction and nitridation. The effects of processing factors, such as raw material mixing methods, C/B2O3 molar ratios, and carbon templates, were systematically studied, and the reaction mechanism was discussed. The experimental results showed that the integrity and morphology of the carbon templates was usually destroyed during ball milling or grinding, but preserved during magnetic stirring. The morphology of synthesized BN particles depended on the C/B2O3 molar ratio in starting reactant mixtures and gradually changed from sheet‐like to near‐spherical shape with decreasing C/B2O3 molar ratio. The morphology and size of synthesized BN particles agreed with that of the carbon templates, which means that the morphology and size of synthesized BN particles can be tailored by controlling that of the carbon template. The BN near‐spherical particles synthesized in this work may be used as thermally conductive fillers for electronic packaging.
{"title":"Synthesis of near‐spherical BN powders by templated carbothermal reduction and nitridation","authors":"Dengke Zhao, Zhaobo Tian, Songmo Du, Shuo Zhao, Binbin Fan, Shijia Zhang, Bohan Wang, Fei Li, Wenbin Cao, Kexin Chen, Guanghua Liu","doi":"10.1111/jace.20138","DOIUrl":"https://doi.org/10.1111/jace.20138","url":null,"abstract":"Boron nitride (BN) powders with near‐spherical particles of more than 10 µm were synthesized by templated carbothermal reduction and nitridation. The effects of processing factors, such as raw material mixing methods, C/B<jats:sub>2</jats:sub>O<jats:sub>3</jats:sub> molar ratios, and carbon templates, were systematically studied, and the reaction mechanism was discussed. The experimental results showed that the integrity and morphology of the carbon templates was usually destroyed during ball milling or grinding, but preserved during magnetic stirring. The morphology of synthesized BN particles depended on the C/B<jats:sub>2</jats:sub>O<jats:sub>3</jats:sub> molar ratio in starting reactant mixtures and gradually changed from sheet‐like to near‐spherical shape with decreasing C/B<jats:sub>2</jats:sub>O<jats:sub>3</jats:sub> molar ratio. The morphology and size of synthesized BN particles agreed with that of the carbon templates, which means that the morphology and size of synthesized BN particles can be tailored by controlling that of the carbon template. The BN near‐spherical particles synthesized in this work may be used as thermally conductive fillers for electronic packaging.","PeriodicalId":200,"journal":{"name":"Journal of the American Ceramic Society","volume":null,"pages":null},"PeriodicalIF":3.9,"publicationDate":"2024-09-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142257195","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Gallium oxide (Ga2O3) has attracted much attention due to its promising applications in optical and electronic devices, while it is difficult to fabricate high‐quality Ga2O3 transparent ceramics because of the non‐cubic crystal structure. In this work, fully densified undoped and rare earth (RE = Tb, Dy. Er)‐doped Ga2O3 transparent ceramics were successfully fabricated by using spark plasma sintering (SPS) and co‐precipitated ceramic powders. Both the powders and ceramics showed pure monoclinic β‐ Ga2O3 crystal structure and unique orientation. After sintering by SPS for 30 min, all the ceramics reached a relative density higher than 99.21%. The total transmittance of RE‐doped Ga2O3 transparent ceramics ranges from 60% to 69% originating from the oriented and dense microstructures. The photoluminescence spectra and fluorescence lifetime of RE‐doped Ga2O3 transparent ceramics confirm characteristics of energy transfers corresponding to Tb3+, Dy3+, or Er3+ ions in the visible and NIR spectral region. This study demonstrates that oriented RE‐doped Ga2O3 transparent ceramics have great potential to be used in various optical applications.
{"title":"Transparent rare earth‐doped gallium oxide ceramics with oriented microstructure","authors":"Jiao Li, Guangran Zhang, Yiquan Wu","doi":"10.1111/jace.20121","DOIUrl":"https://doi.org/10.1111/jace.20121","url":null,"abstract":"Gallium oxide (Ga<jats:sub>2</jats:sub>O<jats:sub>3</jats:sub>) has attracted much attention due to its promising applications in optical and electronic devices, while it is difficult to fabricate high‐quality Ga<jats:sub>2</jats:sub>O<jats:sub>3</jats:sub> transparent ceramics because of the non‐cubic crystal structure. In this work, fully densified undoped and rare earth (RE = Tb, Dy. Er)‐doped Ga<jats:sub>2</jats:sub>O<jats:sub>3</jats:sub> transparent ceramics were successfully fabricated by using spark plasma sintering (SPS) and co‐precipitated ceramic powders. Both the powders and ceramics showed pure monoclinic <jats:italic>β</jats:italic>‐ Ga<jats:sub>2</jats:sub>O<jats:sub>3</jats:sub> crystal structure and unique orientation. After sintering by SPS for 30 min, all the ceramics reached a relative density higher than 99.21%. The total transmittance of RE‐doped Ga<jats:sub>2</jats:sub>O<jats:sub>3</jats:sub> transparent ceramics ranges from 60% to 69% originating from the oriented and dense microstructures. The photoluminescence spectra and fluorescence lifetime of RE‐doped Ga<jats:sub>2</jats:sub>O<jats:sub>3</jats:sub> transparent ceramics confirm characteristics of energy transfers corresponding to Tb<jats:sup>3+</jats:sup>, Dy<jats:sup>3+</jats:sup>, or Er<jats:sup>3+</jats:sup> ions in the visible and NIR spectral region. This study demonstrates that oriented RE‐doped Ga<jats:sub>2</jats:sub>O<jats:sub>3</jats:sub> transparent ceramics have great potential to be used in various optical applications.","PeriodicalId":200,"journal":{"name":"Journal of the American Ceramic Society","volume":null,"pages":null},"PeriodicalIF":3.9,"publicationDate":"2024-09-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142257197","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Kangkang Yuan, Chen Shu, Kexin Meng, Wenjun Zhao, Guosheng Sun, Jien Zhu, Jin Chen, Yunlong Huang, Chengshun Li, Xiaotong Jin
Calcium zirconate (CaZrO3)‐based fibrous membrane is a promising candidate in high‐temperature areas for its high melting point, good phase stability up to 1900°C, low thermal conductivity, and low cost. To further enhance the high temperature flexibility of CaZrO3‐based fibrous membrane without sacrificing stability, modification methods should be conducted. In the present work, a CaZrO3‐BaZrO3 dual‐phasic structure was proposed to modify the high‐temperature properties from the standpoint of phase competition. CaZrO3‐BaZrO3 fibrous membranes were prepared with the combination of the electrospinning method and pyrolysis process. The decomposition process, phase transformation, crystallize size, and microstructure evolution of CaZrO3‐BaZrO3 precursor fibrous membrane were characterized. The grain size, particle size, NIR reflectivity, high‐temperature stability, fire retardancy, and high‐temperature flexibility were also characterized and compared with other CaZrO3‐based fibrous membranes. The higher thermal stability and flexibility of the CaZrO3‐BaZrO3 fibrous membrane at 1200°C would make it a good candidate for high‐temperature insulating, high‐temperature supporting, and high‐temperature filtration.
{"title":"Electrospun CaZrO3‐BaZrO3 fibrous membrane with enhanced high‐temperature stability and flexibility","authors":"Kangkang Yuan, Chen Shu, Kexin Meng, Wenjun Zhao, Guosheng Sun, Jien Zhu, Jin Chen, Yunlong Huang, Chengshun Li, Xiaotong Jin","doi":"10.1111/jace.20146","DOIUrl":"https://doi.org/10.1111/jace.20146","url":null,"abstract":"Calcium zirconate (CaZrO<jats:sub>3</jats:sub>)‐based fibrous membrane is a promising candidate in high‐temperature areas for its high melting point, good phase stability up to 1900°C, low thermal conductivity, and low cost. To further enhance the high temperature flexibility of CaZrO<jats:sub>3</jats:sub>‐based fibrous membrane without sacrificing stability, modification methods should be conducted. In the present work, a CaZrO<jats:sub>3</jats:sub>‐BaZrO<jats:sub>3</jats:sub> dual‐phasic structure was proposed to modify the high‐temperature properties from the standpoint of phase competition. CaZrO<jats:sub>3</jats:sub>‐BaZrO<jats:sub>3</jats:sub> fibrous membranes were prepared with the combination of the electrospinning method and pyrolysis process. The decomposition process, phase transformation, crystallize size, and microstructure evolution of CaZrO<jats:sub>3</jats:sub>‐BaZrO<jats:sub>3</jats:sub> precursor fibrous membrane were characterized. The grain size, particle size, NIR reflectivity, high‐temperature stability, fire retardancy, and high‐temperature flexibility were also characterized and compared with other CaZrO<jats:sub>3</jats:sub>‐based fibrous membranes. The higher thermal stability and flexibility of the CaZrO<jats:sub>3</jats:sub>‐BaZrO<jats:sub>3</jats:sub> fibrous membrane at 1200°C would make it a good candidate for high‐temperature insulating, high‐temperature supporting, and high‐temperature filtration.","PeriodicalId":200,"journal":{"name":"Journal of the American Ceramic Society","volume":null,"pages":null},"PeriodicalIF":3.9,"publicationDate":"2024-09-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142269206","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Xianzi Li, Yanhang Wang, Penghui Yang, Xianyin Yin, Tao Han, Bin Han, Kun He
Topological constraint theory (TCT) and molecular dynamics simulations (MD) are utilized to study the effect of Y2O3/SiO2 substitution on the short‐ and medium‐range structures and properties in aluminosilicate glasses containing Y2O3. Experimental methods have been applied to characterize the structures of the as‐prepared glasses to verify the accuracy of MD simulations. It was found that the Y–O bond distance is around 2.38 Å and the Y average coordination number is around 5.78. The introduction of Y2O3 disrupts the Si–O and Al–O bonds in the network structure and elevates the proportion of non‐bridging oxygen. Meanwhile, the calculation results of Si–O and Al–O bond distances show Y shortens the distance between Si, Al cations and oxygen ions, improving the network structure tightness. Furthermore, the glass transition temperature (Tg), Vickers hardness (HV), and elastic modulus (E) of glass increase with the increase of Y2O3 content, while the viscosity decreases. TCT was used to analyze the relationship among glass compositions, structures, and properties, and the properties prediction models for Tg, HV, and E were established. The effectiveness of TCT prediction models was proved by the comparison between the results predicted by the models and the data reported in the literature.
{"title":"Topological models of yttrium aluminosilicate glass based on molecular dynamics and structure characterization analysis","authors":"Xianzi Li, Yanhang Wang, Penghui Yang, Xianyin Yin, Tao Han, Bin Han, Kun He","doi":"10.1111/jace.20118","DOIUrl":"https://doi.org/10.1111/jace.20118","url":null,"abstract":"Topological constraint theory (TCT) and molecular dynamics simulations (MD) are utilized to study the effect of Y<jats:sub>2</jats:sub>O<jats:sub>3</jats:sub>/SiO<jats:sub>2</jats:sub> substitution on the short‐ and medium‐range structures and properties in aluminosilicate glasses containing Y<jats:sub>2</jats:sub>O<jats:sub>3</jats:sub>. Experimental methods have been applied to characterize the structures of the as‐prepared glasses to verify the accuracy of MD simulations. It was found that the Y–O bond distance is around 2.38 Å and the Y average coordination number is around 5.78. The introduction of Y<jats:sub>2</jats:sub>O<jats:sub>3</jats:sub> disrupts the Si–O and Al–O bonds in the network structure and elevates the proportion of non‐bridging oxygen. Meanwhile, the calculation results of Si–O and Al–O bond distances show Y shortens the distance between Si, Al cations and oxygen ions, improving the network structure tightness. Furthermore, the glass transition temperature (<jats:italic>T<jats:sub>g</jats:sub></jats:italic>), Vickers hardness (<jats:italic>H<jats:sub>V</jats:sub></jats:italic>), and elastic modulus (<jats:italic>E</jats:italic>) of glass increase with the increase of Y<jats:sub>2</jats:sub>O<jats:sub>3</jats:sub> content, while the viscosity decreases. TCT was used to analyze the relationship among glass compositions, structures, and properties, and the properties prediction models for <jats:italic>T<jats:sub>g</jats:sub></jats:italic>, <jats:italic>H<jats:sub>V</jats:sub></jats:italic>, and <jats:italic>E</jats:italic> were established. The effectiveness of TCT prediction models was proved by the comparison between the results predicted by the models and the data reported in the literature.","PeriodicalId":200,"journal":{"name":"Journal of the American Ceramic Society","volume":null,"pages":null},"PeriodicalIF":3.9,"publicationDate":"2024-09-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142257198","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Phosphate invert glasses (PIGs) exhibit excellent biocompatibility because of their high chemical durability and controlled ion releasability. PIGs are composed of short phosphate units such as ortho‐ and pyrophosphate. This structure makes it difficult to obtain clear glass using the melt‐quenching method. Our previous work reported that intermediate oxides (such as TiO2 and Nb2O5)‐containing PIGs exhibit good glass‐forming ability and ion dissolution controllability. This work used a liquid‐phase method to prepare PIGs at room temperature and pressure. Furthermore, TiO2 was used to control ion releasability for biomedical applications. Titanium‐containing PIGs were successfully prepared using a liquid‐phase method. Pyrophosphate and titania formed P‐O‐Ti bonds with an increasing TiO2 content in the glass, forming chain‐like structural units such as (‐O‐P‐O‐P‐O‐Ti‐O‐)n. The number of chain‐like structures increased with an increasing TiO2 content in the glass, improving the chemical durability. Hence, the ion releasability of titanium‐containing PIGs prepared using the liquid‐phase method can be controlled by the glass structure. Additionally, the PIGs exhibited good cell viability. Therefore, the PIGs are candidates for carriers of therapeutic inorganic ions for biomedical applications.
{"title":"Preparation and structure of titanium‐containing pyrophosphate glasses prepared using the liquid‐phase method","authors":"Sungho Lee, Shota Shiraki, Minori Takahashi, Akiko Obata, Makoto Sakurai, Fukue Nagata","doi":"10.1111/jace.20144","DOIUrl":"https://doi.org/10.1111/jace.20144","url":null,"abstract":"Phosphate invert glasses (PIGs) exhibit excellent biocompatibility because of their high chemical durability and controlled ion releasability. PIGs are composed of short phosphate units such as ortho‐ and pyrophosphate. This structure makes it difficult to obtain clear glass using the melt‐quenching method. Our previous work reported that intermediate oxides (such as TiO<jats:sub>2</jats:sub> and Nb<jats:sub>2</jats:sub>O<jats:sub>5</jats:sub>)‐containing PIGs exhibit good glass‐forming ability and ion dissolution controllability. This work used a liquid‐phase method to prepare PIGs at room temperature and pressure. Furthermore, TiO<jats:sub>2</jats:sub> was used to control ion releasability for biomedical applications. Titanium‐containing PIGs were successfully prepared using a liquid‐phase method. Pyrophosphate and titania formed P‐O‐Ti bonds with an increasing TiO<jats:sub>2</jats:sub> content in the glass, forming chain‐like structural units such as (‐O‐P‐O‐P‐O‐Ti‐O‐)<jats:italic><jats:sub>n</jats:sub></jats:italic>. The number of chain‐like structures increased with an increasing TiO<jats:sub>2</jats:sub> content in the glass, improving the chemical durability. Hence, the ion releasability of titanium‐containing PIGs prepared using the liquid‐phase method can be controlled by the glass structure. Additionally, the PIGs exhibited good cell viability. Therefore, the PIGs are candidates for carriers of therapeutic inorganic ions for biomedical applications.","PeriodicalId":200,"journal":{"name":"Journal of the American Ceramic Society","volume":null,"pages":null},"PeriodicalIF":3.9,"publicationDate":"2024-09-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142257192","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Yu Tian, Wei‐Ming Guo, Yi Liu, Si‐Yuan Tong, Zi‐Jian Huang, Hua‐Tay Lin
This study investigated the synthesis mechanism of tantalum boride (TaB2) powder via the boron/carbothermal reduction method, based on thermodynamic calculations and experimental results. The insufficient presence of the intermediate product B2O3 leads to the emergence of TaC and Ta3B4, while in the presence of a sufficient boron source in the reaction system, the primary products formed include TaB2, TaC, and B2O3, with TaC subsequently reacting with B2O3 and carbon to yield TaB2. TaB2 powder was successfully synthesized at 1500°C with the addition of an excess of 20 wt% B4C. The particle size of the powder was approximately 298 nm, and the oxygen content and carbon content in the powder were 0.6 and 0.1 wt.%, respectively.
{"title":"Synthesis mechanism and characterization of tantalum boride powder prepared by boron/carbothermal reduction","authors":"Yu Tian, Wei‐Ming Guo, Yi Liu, Si‐Yuan Tong, Zi‐Jian Huang, Hua‐Tay Lin","doi":"10.1111/jace.20116","DOIUrl":"https://doi.org/10.1111/jace.20116","url":null,"abstract":"This study investigated the synthesis mechanism of tantalum boride (TaB<jats:sub>2</jats:sub>) powder via the boron/carbothermal reduction method, based on thermodynamic calculations and experimental results. The insufficient presence of the intermediate product B<jats:sub>2</jats:sub>O<jats:sub>3</jats:sub> leads to the emergence of TaC and Ta<jats:sub>3</jats:sub>B<jats:sub>4</jats:sub>, while in the presence of a sufficient boron source in the reaction system, the primary products formed include TaB<jats:sub>2</jats:sub>, TaC, and B<jats:sub>2</jats:sub>O<jats:sub>3</jats:sub>, with TaC subsequently reacting with B<jats:sub>2</jats:sub>O<jats:sub>3</jats:sub> and carbon to yield TaB<jats:sub>2</jats:sub>. TaB<jats:sub>2</jats:sub> powder was successfully synthesized at 1500°C with the addition of an excess of 20 wt% B<jats:sub>4</jats:sub>C. The particle size of the powder was approximately 298 nm, and the oxygen content and carbon content in the powder were 0.6 and 0.1 wt.%, respectively.","PeriodicalId":200,"journal":{"name":"Journal of the American Ceramic Society","volume":null,"pages":null},"PeriodicalIF":3.9,"publicationDate":"2024-09-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142257199","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
In recent years, transparent terbium gallium garnet (TGG) ceramics have garnered significant interest for their application in high‐power Faraday isolators. However, challenges in achieving high transparency have led researchers to explore the addition of various sintering aids as a key strategy to enhance the optical quality of TGG ceramics. Through this work, the effect of germanium (Ge) addition on the microstructure and optical transparency of TGG magneto‐optical ceramics was investigated. TGG powders were synthesized by the co‐precipitation method, and the source Ge was Ge ethoxide added through a ball‐milling step. Transparent TGG ceramics were prepared by air pre‐sintering combined with hot isostatic pressing post‐treatment and subsequent annealing. The ceramics containing 200 ppm Ge exhibit optimal transmittance of 81.3% at 1064 nm (a value of theoretical transmittance), the Verdet constant was −133.0 rad·T−1·m−1 at 633 nm. When the addition of Ge reaches 600 ppm, a secondary phase can be observed on the surface of ceramic. Subsequently, TGG ceramics prepared from 1425°C to 1500°C with 200 ppm of Ge were analyzed, which revealed that the optimal pre‐sintering temperature is 1450°C.
{"title":"Influence of germanium concentration on the microstructure and optical transparency of terbium gallium garnet ceramics","authors":"Xiao Li, Lixuan Zhang, Danyang Zhu, Junlin Wu, Chen Hu, Tingsong Li, Lexiang Wu, Dariusz Hreniak, Jiang Li","doi":"10.1111/jace.20140","DOIUrl":"https://doi.org/10.1111/jace.20140","url":null,"abstract":"In recent years, transparent terbium gallium garnet (TGG) ceramics have garnered significant interest for their application in high‐power Faraday isolators. However, challenges in achieving high transparency have led researchers to explore the addition of various sintering aids as a key strategy to enhance the optical quality of TGG ceramics. Through this work, the effect of germanium (Ge) addition on the microstructure and optical transparency of TGG magneto‐optical ceramics was investigated. TGG powders were synthesized by the co‐precipitation method, and the source Ge was Ge ethoxide added through a ball‐milling step. Transparent TGG ceramics were prepared by air pre‐sintering combined with hot isostatic pressing post‐treatment and subsequent annealing. The ceramics containing 200 ppm Ge exhibit optimal transmittance of 81.3% at 1064 nm (a value of theoretical transmittance), the Verdet constant was −133.0 rad·T<jats:sup>−1</jats:sup>·m<jats:sup>−1</jats:sup> at 633 nm. When the addition of Ge reaches 600 ppm, a secondary phase can be observed on the surface of ceramic. Subsequently, TGG ceramics prepared from 1425°C to 1500°C with 200 ppm of Ge were analyzed, which revealed that the optimal pre‐sintering temperature is 1450°C.","PeriodicalId":200,"journal":{"name":"Journal of the American Ceramic Society","volume":null,"pages":null},"PeriodicalIF":3.9,"publicationDate":"2024-09-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142257193","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Ahmad Sayyadi-Shahraki, Till Frömling, Fangping Zhuo
Dislocations in oxide ceramics significantly influence their physical properties by creating substantial local strain fields, new electronic states, and space-charge layers. In this study, we investigated the effects of mechanically introduced dislocations on the electrical conductivity of BaTiO3 single crystals. High-temperature plastic deformation was employed to introduce a high dislocation density with a {100}〈100〉 slip system. Impedance measurements revealed a significant anisotropy in the conductivity due to the presence of oriented dislocation structures. The crystals with dislocation lines aligned parallel to the measurement axis ([001] crystallographic direction) exhibited 16-fold higher conductivity compared to those measured across the dislocations. Compared to the pristine crystals, this means an increase in conductivity when the measurements were carried out parallel to dislocation lines and a decrease in perpendicular measurements. Our study demonstrates that not only ferroelectric properties but also charge transport can be modified by dislocation introduction in BaTiO3.
{"title":"Tailoring charge transport in BaTiO3 crystals through dislocation engineering","authors":"Ahmad Sayyadi-Shahraki, Till Frömling, Fangping Zhuo","doi":"10.1111/jace.20147","DOIUrl":"https://doi.org/10.1111/jace.20147","url":null,"abstract":"Dislocations in oxide ceramics significantly influence their physical properties by creating substantial local strain fields, new electronic states, and space-charge layers. In this study, we investigated the effects of mechanically introduced dislocations on the electrical conductivity of BaTiO<sub>3</sub> single crystals. High-temperature plastic deformation was employed to introduce a high dislocation density with a {100}〈100〉 slip system. Impedance measurements revealed a significant anisotropy in the conductivity due to the presence of oriented dislocation structures. The crystals with dislocation lines aligned parallel to the measurement axis ([001] crystallographic direction) exhibited 16-fold higher conductivity compared to those measured across the dislocations. Compared to the pristine crystals, this means an increase in conductivity when the measurements were carried out parallel to dislocation lines and a decrease in perpendicular measurements. Our study demonstrates that not only ferroelectric properties but also charge transport can be modified by dislocation introduction in BaTiO<sub>3</sub>.","PeriodicalId":200,"journal":{"name":"Journal of the American Ceramic Society","volume":null,"pages":null},"PeriodicalIF":3.9,"publicationDate":"2024-09-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142257145","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
This study presents the successful synthesis of Sr2Ta2O7 with a pyrochlore crystal structure, which was previously unreported. Traditionally, Sr2Ta2O7 is synthesized in an orthorhombic layered perovskite-type structure using traditional solid-state reaction and batch-type subcritical hydrothermal methods. Here, we utilize a continuous-flow supercritical hydrothermal method, a technique primarily applied for nanoparticle synthesis and minimally explored for the synthesis of metastable crystals. Through detailed evaluations employing X-ray diffraction and scanning electron microscopy, we confirmed the synthesis of the pyrochlore phase, characterized by particles with a diameter of less than 100 nm, synthesized at 633 K. Notably, the synthesized pyrochlore structure demonstrated remarkable stability, even after thermal treatment at 773 K for 1 h. Pyrochlore Sr2Ta2O7 stands out as a rare exception to the traditional tolerance factor approach among 278 known A2B2O7 compositions. Systematic evaluation of formation energies through first-principles calculations revealed that the pyrochlore Sr2Ta2O7 synthesized in this study is located 0.06 eV/atom above the convex hull. This achievement underscores the potential of the continuous-flow supercritical hydrothermal method in automating the exploration and discovery of novel crystal structures, suggesting a systematic pathway for advancing the field of material synthesis.
本研究成功合成了具有热绿体晶体结构的 Sr2Ta2O7，这是以前从未报道过的。传统上，Sr2Ta2O7 是采用传统的固态反应和间歇式亚临界水热法合成的正交层状包晶型结构。在这里，我们采用了一种连续流超临界水热法，这种技术主要用于纳米粒子合成，而很少用于合成可移动晶体。通过使用 X 射线衍射和扫描电子显微镜进行详细评估，我们证实了火成岩相的合成，其特征是在 633 K 下合成的颗粒直径小于 100 nm。通过第一原理计算对形成能进行系统评估后发现，本研究合成的热绿体 Sr2Ta2O7 比凸壳高出 0.06 eV/原子。这一成果凸显了连续流超临界水热法在自动探索和发现新型晶体结构方面的潜力，为推进材料合成领域的发展提供了一条系统化途径。
{"title":"Synthesis of pyrochlore Sr2Ta2O7 via continuous-flow supercritical hydrothermal approach","authors":"Hiroyuki Hayashi, Yuki Matsukuma, Kazunori Murakami, Isao Tanaka","doi":"10.1111/jace.20122","DOIUrl":"https://doi.org/10.1111/jace.20122","url":null,"abstract":"This study presents the successful synthesis of Sr<sub>2</sub>Ta<sub>2</sub>O<sub>7</sub> with a pyrochlore crystal structure, which was previously unreported. Traditionally, Sr<sub>2</sub>Ta<sub>2</sub>O<sub>7</sub> is synthesized in an orthorhombic layered perovskite-type structure using traditional solid-state reaction and batch-type subcritical hydrothermal methods. Here, we utilize a continuous-flow supercritical hydrothermal method, a technique primarily applied for nanoparticle synthesis and minimally explored for the synthesis of metastable crystals. Through detailed evaluations employing X-ray diffraction and scanning electron microscopy, we confirmed the synthesis of the pyrochlore phase, characterized by particles with a diameter of less than 100 nm, synthesized at 633 K. Notably, the synthesized pyrochlore structure demonstrated remarkable stability, even after thermal treatment at 773 K for 1 h. Pyrochlore Sr<sub>2</sub>Ta<sub>2</sub>O<sub>7</sub> stands out as a rare exception to the traditional tolerance factor approach among 278 known A<sub>2</sub>B<sub>2</sub>O<sub>7</sub> compositions. Systematic evaluation of formation energies through first-principles calculations revealed that the pyrochlore Sr<sub>2</sub>Ta<sub>2</sub>O<sub>7</sub> synthesized in this study is located 0.06 eV/atom above the convex hull. This achievement underscores the potential of the continuous-flow supercritical hydrothermal method in automating the exploration and discovery of novel crystal structures, suggesting a systematic pathway for advancing the field of material synthesis.","PeriodicalId":200,"journal":{"name":"Journal of the American Ceramic Society","volume":null,"pages":null},"PeriodicalIF":3.9,"publicationDate":"2024-09-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142257142","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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