In this work, we propose a strategy for in situ construction of rod-like grains in Al2O3-TiO2 ceramics through Ba doping. Ba-doped Al2O3-13 wt% TiO2 composite powder was initially synthesized using combustion synthesis-air atomization, where feedstocks were melted by the Al-O2 combustion reaction and subsequently atomized and rapidly cooled in air, producing quenched powders rich in metastable phases. Upon heat treatment at 1100℃, the metastable phases transformed into stable forms, accompanied by phase separation and solid solution precipitation. Notably, Ba doping induced the formation of rod-like hollandite grains with preferential growth along the [001] direction. Bulk ceramics were prepared through pressureless sintering, and the sample sintered at 1350℃ exhibited a hardness of 14.14±0.61 GPa and a fracture toughness of 5.17±0.49 MPa∙m1/2. The toughening behavior of rod-like grains, including crack deflection and pull-out/bridging effects, was observed. This study provides insights into the evolution of quenched oxides and the design of ceramic microstructures.
{"title":"In situ construction of one-dimensional structures induced by Ba doping in Al2O3-TiO2 ceramics derived from quenched powders","authors":"Yuchen Yuan, Xudong Liu, Yongting Zheng, Renjie Wang, Shiyang Zhu, Canqing Fang, Hang Yin","doi":"10.1016/j.jeurceramsoc.2024.116965","DOIUrl":"10.1016/j.jeurceramsoc.2024.116965","url":null,"abstract":"<div><div>In this work, we propose a strategy for in situ construction of rod-like grains in Al<sub>2</sub>O<sub>3</sub>-TiO<sub>2</sub> ceramics through Ba doping. Ba-doped Al<sub>2</sub>O<sub>3</sub>-13 wt% TiO<sub>2</sub> composite powder was initially synthesized using combustion synthesis-air atomization, where feedstocks were melted by the Al-O<sub>2</sub> combustion reaction and subsequently atomized and rapidly cooled in air, producing quenched powders rich in metastable phases. Upon heat treatment at 1100℃, the metastable phases transformed into stable forms, accompanied by phase separation and solid solution precipitation. Notably, Ba doping induced the formation of rod-like hollandite grains with preferential growth along the [001] direction. Bulk ceramics were prepared through pressureless sintering, and the sample sintered at 1350℃ exhibited a hardness of 14.14±0.61 GPa and a fracture toughness of 5.17±0.49 MPa∙m<sup>1/2</sup>. The toughening behavior of rod-like grains, including crack deflection and pull-out/bridging effects, was observed. This study provides insights into the evolution of quenched oxides and the design of ceramic microstructures.</div></div>","PeriodicalId":17408,"journal":{"name":"Journal of The European Ceramic Society","volume":"45 3","pages":"Article 116965"},"PeriodicalIF":5.8,"publicationDate":"2024-10-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142586439","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-10-18DOI: 10.1016/j.jeurceramsoc.2024.116993
R.W. Harrison , J. Morgan , J. Buckley , S. Bostanchi , D. Pearmain , T. Abram , D. Goddard , N. Barron
Flash sintering (FS) has been shown to enhance the sintering kinetics in UO2. Using a bespoke AC-FS furnace, high density UO2 pellets, >95 % theoretical density (TD) have been produced followed by scale up and Gd2O3 doping trials. Increasing furnace temperature during FS increases pellet density to a plateau, however, increasing hold time and maximum current both increased the density of UO2 samples to >95 % TD and grain size to ∼4 µm, close to conventional sintering (CS). The optimised FS program reduced sintering temperature and cycle time by ∼50 % compared to CS. Scale up trials showed >96 %TD pellets could be achieved for 11.3 and 14.125 mm diameter green bodies, demonstrating typical fuel pellet diameters are feasible with FS. Gd doping experiments showed with 1 wt% Gd2O3 addition, a ∼92 %TD pellet with ∼2 µm grain size was obtainable, highlighting further optimisation is required for mixed oxide (MOx) materials.
{"title":"Flash sintering of UO2 pellets for nuclear fuel and wasteform applications","authors":"R.W. Harrison , J. Morgan , J. Buckley , S. Bostanchi , D. Pearmain , T. Abram , D. Goddard , N. Barron","doi":"10.1016/j.jeurceramsoc.2024.116993","DOIUrl":"10.1016/j.jeurceramsoc.2024.116993","url":null,"abstract":"<div><div>Flash sintering (FS) has been shown to enhance the sintering kinetics in UO<sub>2</sub>. Using a bespoke AC-FS furnace, high density UO<sub>2</sub> pellets, >95 % theoretical density (TD) have been produced followed by scale up and Gd<sub>2</sub>O<sub>3</sub> doping trials. Increasing furnace temperature during FS increases pellet density to a plateau, however, increasing hold time and maximum current both increased the density of UO<sub>2</sub> samples to >95 % TD and grain size to ∼4 µm, close to conventional sintering (CS). The optimised FS program reduced sintering temperature and cycle time by ∼50 % compared to CS. Scale up trials showed >96 %TD pellets could be achieved for 11.3 and 14.125 mm diameter green bodies, demonstrating typical fuel pellet diameters are feasible with FS. Gd doping experiments showed with 1 wt% Gd<sub>2</sub>O<sub>3</sub> addition, a ∼92 %TD pellet with ∼2 µm grain size was obtainable, highlighting further optimisation is required for mixed oxide (MOx) materials.</div></div>","PeriodicalId":17408,"journal":{"name":"Journal of The European Ceramic Society","volume":"45 3","pages":"Article 116993"},"PeriodicalIF":5.8,"publicationDate":"2024-10-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142527643","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-10-18DOI: 10.1016/j.jeurceramsoc.2024.116997
Nadejda Horchidan , Vlad Alexandru Lukacs , Mihai Asandulesa , George Stoian , Cristina Elena Ciomaga , Liliana Mitoseriu
This study investigates BaGexTi1-xO3 ceramics with varying compositions (x = 0.010, 0.018, 0.100) produced by solid-state reaction, exploring the impact of composition and sintering temperatures (1150 °C, 1200 °C, 1300 °C) on functional characteristics (low-field dielectric, tunability, ferroelectric switching). Increasing Ge amount and sintering temperatures enhances sinterability of BaGexTi1-xO3 to almost complete densification. Room temperature permittivity ranges from 1000 to 2000, with dielectric losses below 10%. For small Ge additions, the dielectric behavior and phase transitions mirror BaTiO3 ceramics. Increasing Ge addition results in a slight increase of the Curie temperature. Dielectric relaxation mechanisms involve two activation energy ranges related to oxygen vacancies and ionic conduction. Ceramics with larger grain sizes exhibit well-defined ferroelectric P(E) loops, while fine-grained ones contain extrinsic contributions. The highest tunability performances are found for the lowest Ge additions, sintered at 1150 °C, which are able to withstand the application of the highest dc field.
本研究调查了通过固态反应生产的不同成分（x = 0.010、0.018、0.100）的 BaGexTi1-xO3 陶瓷，探讨了成分和烧结温度（1150 °C、1200 °C、1300 °C）对功能特性（低场介电、可调性、铁电开关）的影响。增加 Ge 的用量和烧结温度可提高 BaGexTi1-xO3 的烧结性，使其几乎完全致密化。室温介电常数在 1000 到 2000 之间，介电损耗低于 10%。在添加少量 Ge 的情况下，介电行为和相变反映了 BaTiO3 陶瓷。增加 Ge 添加量会导致居里温度略有上升。介电弛豫机制涉及与氧空位和离子传导有关的两个活化能范围。晶粒尺寸较大的陶瓷表现出定义明确的铁电 P(E) 环，而晶粒较细的陶瓷则包含外在贡献。在 1150 °C 下烧结的 Ge 添加量最低的陶瓷具有最高的可调谐性能，能够承受最高直流电场的应用。
{"title":"Exploring grain size and composition effects on the functional properties of BaGexTi1-xO3 ceramics","authors":"Nadejda Horchidan , Vlad Alexandru Lukacs , Mihai Asandulesa , George Stoian , Cristina Elena Ciomaga , Liliana Mitoseriu","doi":"10.1016/j.jeurceramsoc.2024.116997","DOIUrl":"10.1016/j.jeurceramsoc.2024.116997","url":null,"abstract":"<div><div>This study investigates BaGe<sub>x</sub>Ti<sub>1-x</sub>O<sub>3</sub> ceramics with varying compositions (x = 0.010, 0.018, 0.100) produced by solid-state reaction, exploring the impact of composition and sintering temperatures (1150 °C, 1200 °C, 1300 °C) on functional characteristics (low-field dielectric, tunability, ferroelectric switching). Increasing Ge amount and sintering temperatures enhances sinterability of BaGe<sub>x</sub>Ti<sub>1-x</sub>O<sub>3</sub> to almost complete densification. Room temperature permittivity ranges from 1000 to 2000, with dielectric losses below 10%. For small Ge additions, the dielectric behavior and phase transitions mirror BaTiO<sub>3</sub> ceramics. Increasing Ge addition results in a slight increase of the Curie temperature. Dielectric relaxation mechanisms involve two activation energy ranges related to oxygen vacancies and ionic conduction. Ceramics with larger grain sizes exhibit well-defined ferroelectric P(E) loops, while fine-grained ones contain extrinsic contributions. The highest tunability performances are found for the lowest Ge additions, sintered at 1150 °C, which are able to withstand the application of the highest dc field.</div></div>","PeriodicalId":17408,"journal":{"name":"Journal of The European Ceramic Society","volume":"45 3","pages":"Article 116997"},"PeriodicalIF":5.8,"publicationDate":"2024-10-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142539898","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-10-18DOI: 10.1016/j.jeurceramsoc.2024.116996
Yichen Chen , Liping Pan , Yawei Li , Ning Liao , Qingyou Zhu
Corundum-spinel castable is a vital refractory material used in steel ladle linings. Conventional approaches for assessing the thermal shock resistance of corundum-spinel refractory are not entirely representative of the actual application scenarios. This study investigates the influence of spinel-calcium aluminate composite aggregate on the thermal shock resistance of corundum castable using supersonic frequency induction heating technology. The research uncovers how CMA aggregate enhances the thermal shock resistance of corundum castable by cyclic thermal shock tests under varying operational conditions. Results reveal that the incorporation of CMA aggregate led to significant improvements in cold crushing strength and strength retention ratio following thermal shocks. The observed enhancement predominantly stems from the presence of CA/CA2 phase within the CMA aggregate, which undergoes a solid-liquid phase transition at high temperatures, enabling the absorption and retention of substantial heat and aiding in the repair of microcracks within the materials and at the interfacial regions.
{"title":"Phase transition heat storage and self-healing mechanism of spinel-calcium aluminate composite aggregate in corundum castable","authors":"Yichen Chen , Liping Pan , Yawei Li , Ning Liao , Qingyou Zhu","doi":"10.1016/j.jeurceramsoc.2024.116996","DOIUrl":"10.1016/j.jeurceramsoc.2024.116996","url":null,"abstract":"<div><div>Corundum-spinel castable is a vital refractory material used in steel ladle linings. Conventional approaches for assessing the thermal shock resistance of corundum-spinel refractory are not entirely representative of the actual application scenarios. This study investigates the influence of spinel-calcium aluminate composite aggregate on the thermal shock resistance of corundum castable using supersonic frequency induction heating technology. The research uncovers how CMA aggregate enhances the thermal shock resistance of corundum castable by cyclic thermal shock tests under varying operational conditions. Results reveal that the incorporation of CMA aggregate led to significant improvements in cold crushing strength and strength retention ratio following thermal shocks. The observed enhancement predominantly stems from the presence of CA/CA<sub>2</sub> phase within the CMA aggregate, which undergoes a solid-liquid phase transition at high temperatures, enabling the absorption and retention of substantial heat and aiding in the repair of microcracks within the materials and at the interfacial regions.</div></div>","PeriodicalId":17408,"journal":{"name":"Journal of The European Ceramic Society","volume":"45 3","pages":"Article 116996"},"PeriodicalIF":5.8,"publicationDate":"2024-10-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142527609","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-10-18DOI: 10.1016/j.jeurceramsoc.2024.116999
Xinyu Wang, Wei Feng, Xuechao Wang, Lefan Yang, Jian Chen, Ping Wang, Lei Liu
C/C-SiC-AlSi composites with uniform distribution of SiC ceramic phase were prepared by ultrasound-assisted slurry injection combined with the PIP+PI process. Ablation tests were performed by alternant plasma and surface cooling airflow for 0.2 s×200 cycles under the flame temperature of 2600 K. Results showed that the mass and linear ablation rates continued to decrease with the increasing of airflow rate from 0 to 3 m3/h, the minimum ablation rates were 0.1525 mg/s and 3.1725 μm/s, respectively. Micro-morphologies and surface temperature analysis suggested that ablation behavior of the composites was affected by the cooling effect of airflow and mechanical erosion. On the one hand, surface temperature of composites reduced and local physical and chemical reactions of the composites alleviated; on the other hand, the increase of airflow rate caused surface cracks and fragments of the composites. According to the ablation results, the former should play a leading role more than the latter.
{"title":"Effect of surface air cooling on the high frequent cyclic ablation of C/C-SiC-AlSi composite prepared by slurry injection technique","authors":"Xinyu Wang, Wei Feng, Xuechao Wang, Lefan Yang, Jian Chen, Ping Wang, Lei Liu","doi":"10.1016/j.jeurceramsoc.2024.116999","DOIUrl":"10.1016/j.jeurceramsoc.2024.116999","url":null,"abstract":"<div><div>C/C-SiC-AlSi composites with uniform distribution of SiC ceramic phase were prepared by ultrasound-assisted slurry injection combined with the PIP+PI process. Ablation tests were performed by alternant plasma and surface cooling airflow for 0.2 s×200 cycles under the flame temperature of 2600 K. Results showed that the mass and linear ablation rates continued to decrease with the increasing of airflow rate from 0 to 3 m<sup>3</sup>/h, the minimum ablation rates were 0.1525 mg/s and 3.1725 μm/s, respectively. Micro-morphologies and surface temperature analysis suggested that ablation behavior of the composites was affected by the cooling effect of airflow and mechanical erosion. On the one hand, surface temperature of composites reduced and local physical and chemical reactions of the composites alleviated; on the other hand, the increase of airflow rate caused surface cracks and fragments of the composites. According to the ablation results, the former should play a leading role more than the latter.</div></div>","PeriodicalId":17408,"journal":{"name":"Journal of The European Ceramic Society","volume":"45 3","pages":"Article 116999"},"PeriodicalIF":5.8,"publicationDate":"2024-10-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142527707","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The main objective of this study is to investigate the influence of several experimental parameters on the evolution of the joint microstructure and interfaces during brazing of zirconia with titanium using pure gold foils 25–150 µm thick. The brazing experiments were carried out under high vacuum at 1080–1100°C with 3–60 minutes of holding time. Cross sections of the joints were characterized by SEM with EDX analysis, TEM and X-ray diffraction. Four intermetallics and a Ti-Au solid solution were formed at Au / Ti interface and a submicron Ti2O3 layer at Au / ZrO2 interface. The interdiffusion in Au-Ti intermetallics is so fast that brazing with thin gold foils (25–50 µm) can lead to a total consumption of the liquid Au. To avoid isothermal solidification of the joint and obtain a thin and continuous Ti2O3 layer, low temperature, thick gold foil and short holding time are recommended for the brazing process.
{"title":"Brazing of zirconia to titanium using pure gold: Physicochemical aspects","authors":"Marie Fischer , Valérie Chaumat , Camille Flament , Fiqiri Hodaj","doi":"10.1016/j.jeurceramsoc.2024.117000","DOIUrl":"10.1016/j.jeurceramsoc.2024.117000","url":null,"abstract":"<div><div>The main objective of this study is to investigate the influence of several experimental parameters on the evolution of the joint microstructure and interfaces during brazing of zirconia with titanium using pure gold foils 25–150 µm thick. The brazing experiments were carried out under high vacuum at 1080–1100°C with 3–60 minutes of holding time. Cross sections of the joints were characterized by SEM with EDX analysis, TEM and X-ray diffraction. Four intermetallics and a Ti-Au solid solution were formed at Au / Ti interface and a submicron Ti<sub>2</sub>O<sub>3</sub> layer at Au / ZrO<sub>2</sub> interface. The interdiffusion in Au-Ti intermetallics is so fast that brazing with thin gold foils (25–50 µm) can lead to a total consumption of the liquid Au. To avoid isothermal solidification of the joint and obtain a thin and continuous Ti<sub>2</sub>O<sub>3</sub> layer, low temperature, thick gold foil and short holding time are recommended for the brazing process.</div></div>","PeriodicalId":17408,"journal":{"name":"Journal of The European Ceramic Society","volume":"45 3","pages":"Article 117000"},"PeriodicalIF":5.8,"publicationDate":"2024-10-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142572809","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-10-17DOI: 10.1016/j.jeurceramsoc.2024.116995
Lang Xiao , Weiping Gong , Zhao-hui Long , Jiahui Zhao , Duoduo Zhang , Ting Wang , Kai Li , Alexandra Navrotsky
Formation kinetics and equilibrium thermodynamics are fundamental knowledge for predicting microstructure and properties during materials processing and utilization. This work prepared high purity Bi12TiO20, Bi4Ti3O12 and Bi2Ti4O11 compounds and characterized these compounds by in-suit X-ray diffraction, scanning electron microscope, energy dispersive spectrometer as well as calorimetry. Based on the experimental data obtained in this work and the literature, a thermodynamic description of the Bi2O3–TiO2 system was carried out, a thermodynamic database as well as the calculated phase diagram of the system was provided. The discrepancy between the present calculation with the experimental data were discussed, the formation kinetics of the compounds was explained and the bismuth titanate ceramics with tailored structure and specific physical properties were sintered.
形成动力学和平衡热力学是预测材料加工和利用过程中微观结构和性能的基础知识。本研究制备了高纯度的 Bi12TiO20、Bi4Ti3O12 和 Bi2Ti4O11 化合物，并通过 X 射线衍射、扫描电子显微镜、能谱仪和量热仪对这些化合物进行了表征。根据本研究获得的实验数据和文献资料，对 Bi2O3-TiO2 体系进行了热力学描述，并提供了该体系的热力学数据库和计算相图。讨论了当前计算与实验数据之间的差异，解释了化合物的形成动力学，并烧结出了具有定制结构和特定物理性质的钛酸铋陶瓷。
{"title":"Formation kinetics and equilibrium thermodynamics study on the Bi2O3-TiO2 system for synthesis of the bismuth titanate ceramics","authors":"Lang Xiao , Weiping Gong , Zhao-hui Long , Jiahui Zhao , Duoduo Zhang , Ting Wang , Kai Li , Alexandra Navrotsky","doi":"10.1016/j.jeurceramsoc.2024.116995","DOIUrl":"10.1016/j.jeurceramsoc.2024.116995","url":null,"abstract":"<div><div>Formation kinetics and equilibrium thermodynamics are fundamental knowledge for predicting microstructure and properties during materials processing and utilization. This work prepared high purity Bi<sub>12</sub>TiO<sub>20</sub>, Bi<sub>4</sub>Ti<sub>3</sub>O<sub>12</sub> and Bi<sub>2</sub>Ti<sub>4</sub>O<sub>11</sub> compounds and characterized these compounds by in-suit X-ray diffraction, scanning electron microscope, energy dispersive spectrometer as well as calorimetry. Based on the experimental data obtained in this work and the literature, a thermodynamic description of the Bi<sub>2</sub>O<sub>3</sub>–TiO<sub>2</sub> system was carried out, a thermodynamic database as well as the calculated phase diagram of the system was provided. The discrepancy between the present calculation with the experimental data were discussed, the formation kinetics of the compounds was explained and the bismuth titanate ceramics with tailored structure and specific physical properties were sintered.</div></div>","PeriodicalId":17408,"journal":{"name":"Journal of The European Ceramic Society","volume":"45 3","pages":"Article 116995"},"PeriodicalIF":5.8,"publicationDate":"2024-10-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142593773","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-10-16DOI: 10.1016/j.jeurceramsoc.2024.116989
Akinori Kan , Yuta Niwa , Susumu Takahashi , Hirotaka Ogawa
The influence of Ca substitution for R (R = La, Nd, Sm, Gd, Dy, Y, and Yb) on the electrical conductivity of double perovskite-structured Ba2R1-xCaxNbO6-δ (x = 0 and 0.2) ceramics was characterized in this study. Crystal structure analysis of Ba2R0.8Ca0.2NbO6-δ showed three types of lattices, monoclinic (R= La and Nd), tetragonal (R= Sm, Gd, and Dy) and cubic (R= Y and Yb), resulting the reduction of structural distortion for monoclinic structure by the Ca substitution for R. The significant differences in the electrical conductivity between the Ba2LaNbO6 and Ba2La0.8Ca0.2NbO6-δ ceramics may be related to the decrease in the structural distortion, as suggested by the changes in HT-XRPD patterns. Ba2La0.8Ca0.2NbO6 ceramic exhibited the highest electrical conductivity of 2.21 × 10−3 S/cm at 800 ℃ measured under a wet 1 % H2/Ar atmosphere. EMF measurements using a hydrogen concentration cell with water vapor and a water vapor concentration cell revealed that the predominant charge carriers in the Ba2R1-xCaxNbO6-δ ceramics were protons in the temperature range of 600–800 ℃.
{"title":"Proton conductivity of Ca-doped Ba2R1-xCaxNbO6-δ (R = La, Nd, Sm, Gd, Dy, Y, and Yb) ceramics with double perovskite structure","authors":"Akinori Kan , Yuta Niwa , Susumu Takahashi , Hirotaka Ogawa","doi":"10.1016/j.jeurceramsoc.2024.116989","DOIUrl":"10.1016/j.jeurceramsoc.2024.116989","url":null,"abstract":"<div><div>The influence of Ca substitution for <em>R</em> (<em>R</em> = La, Nd, Sm, Gd, Dy, Y, and Yb) on the electrical conductivity of double perovskite-structured Ba<sub>2</sub><em>R</em><sub>1-<em>x</em></sub>Ca<sub><em>x</em></sub>NbO<sub>6-δ</sub> (<em>x</em> = 0 and 0.2) ceramics was characterized in this study. Crystal structure analysis of Ba<sub>2</sub><em>R</em><sub>0.8</sub>Ca<sub>0.2</sub>NbO<sub>6-δ</sub> showed three types of lattices, monoclinic (<em>R</em>= La and Nd), tetragonal (<em>R</em>= Sm, Gd, and Dy) and cubic (<em>R</em>= Y and Yb), resulting the reduction of structural distortion for monoclinic structure by the Ca substitution for <em>R</em>. The significant differences in the electrical conductivity between the Ba<sub>2</sub>LaNbO<sub>6</sub> and Ba<sub>2</sub>La<sub>0.8</sub>Ca<sub>0.2</sub>NbO<sub>6-δ</sub> ceramics may be related to the decrease in the structural distortion, as suggested by the changes in HT-XRPD patterns. Ba<sub>2</sub>La<sub>0.8</sub>Ca<sub>0.2</sub>NbO<sub>6</sub> ceramic exhibited the highest electrical conductivity of 2.21 × 10<sup>−3</sup> S/cm at 800 ℃ measured under a wet 1 % H<sub>2</sub>/Ar atmosphere. EMF measurements using a hydrogen concentration cell with water vapor and a water vapor concentration cell revealed that the predominant charge carriers in the Ba<sub>2</sub><em>R</em><sub>1-<em>x</em></sub>Ca<sub><em>x</em></sub>NbO<sub>6-δ</sub> ceramics were protons in the temperature range of 600–800 ℃.</div></div>","PeriodicalId":17408,"journal":{"name":"Journal of The European Ceramic Society","volume":"45 3","pages":"Article 116989"},"PeriodicalIF":5.8,"publicationDate":"2024-10-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142527610","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-10-16DOI: 10.1016/j.jeurceramsoc.2024.116990
Shaoyong Qin , Changhai Zhang , Jiaji Zhang , Zaichun Sun , Wuxiao Wang , Lei Xu
Cr3+: SrF2 nanopowders were synthesized using a chemical co-precipitation method. The nanoparticles exhibited a structure consistent with the pure SrF2 phase. Cr3+: SrF2 transparent ceramics were fabricated by hot-pressed (HP) sintering technique. The transmittance of 1 at% Cr3+: SrF2 transparent ceramics reached up to 83 % at 1054 nm, which is superior to other SrF2 transparent ceramics with different Cr3+ doping concentration. Furthermore, the mechanical properties of Cr3+: SrF2 transparent ceramics improved with increasing Cr3+ doping levels. The 1 at% Cr3+: SrF2 transparent ceramics exhibited the best mechanical properties, with a microhardness of 2.573 GPa, fracture toughness of 0.70 MPa·m1/2, and compressive strength of 38.1 MPa. The luminescence spectra and fluorescence lifetimes of the SrF2 transparent ceramics as a function of Cr3+ doping concentration were also analyzed and discussed.
{"title":"Effect of Cr3+ doping concentration on the microstructure, mechanical properties and optical properties of Cr3+: SrF2 transparent ceramics","authors":"Shaoyong Qin , Changhai Zhang , Jiaji Zhang , Zaichun Sun , Wuxiao Wang , Lei Xu","doi":"10.1016/j.jeurceramsoc.2024.116990","DOIUrl":"10.1016/j.jeurceramsoc.2024.116990","url":null,"abstract":"<div><div>Cr<sup>3+</sup>: SrF<sub>2</sub> nanopowders were synthesized using a chemical co-precipitation method. The nanoparticles exhibited a structure consistent with the pure SrF<sub>2</sub> phase. Cr<sup>3+</sup>: SrF<sub>2</sub> transparent ceramics were fabricated by hot-pressed (HP) sintering technique. The transmittance of 1 at% Cr<sup>3+</sup>: SrF<sub>2</sub> transparent ceramics reached up to 83 % at 1054 nm, which is superior to other SrF<sub>2</sub> transparent ceramics with different Cr<sup>3+</sup> doping concentration. Furthermore, the mechanical properties of Cr<sup>3+</sup>: SrF<sub>2</sub> transparent ceramics improved with increasing Cr<sup>3+</sup> doping levels. The 1 at% Cr<sup>3+</sup>: SrF<sub>2</sub> transparent ceramics exhibited the best mechanical properties, with a microhardness of 2.573 GPa, fracture toughness of 0.70 MPa·m<sup>1/2</sup>, and compressive strength of 38.1 MPa. The luminescence spectra and fluorescence lifetimes of the SrF<sub>2</sub> transparent ceramics as a function of Cr<sup>3+</sup> doping concentration were also analyzed and discussed.</div></div>","PeriodicalId":17408,"journal":{"name":"Journal of The European Ceramic Society","volume":"45 3","pages":"Article 116990"},"PeriodicalIF":5.8,"publicationDate":"2024-10-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142444738","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-10-15DOI: 10.1016/j.jeurceramsoc.2024.116991
D. Keith Coffman , Shen J. Dillon
The master sintering curve was developed assuming diffusion-limited coarsening and densification kinetics. A key limitation of the model is that it is only valid for a single set of initial conditions, i.e., grain size and density. Recent in situ sintering experiments suggest that densification follows nucleation-limited kinetics. A model for sintering can be formulated based on a thermodynamic energy balance between interfacial energy dissipation and work required to overcome the nucleation barrier. A feature of this model is that it inherently relates coarsening and densification, providing a basis for formulating a generalized master sintering curve that is not sensitive to initial conditions. This paper develops the model and demonstrates its practical application to several oxide systems, including ZnO, Al2O3, and Y2O3-doped tetragonal ZrO2.
{"title":"A generalized master sintering curve based on nucleation-limited densification kinetics","authors":"D. Keith Coffman , Shen J. Dillon","doi":"10.1016/j.jeurceramsoc.2024.116991","DOIUrl":"10.1016/j.jeurceramsoc.2024.116991","url":null,"abstract":"<div><div>The master sintering curve was developed assuming diffusion-limited coarsening and densification kinetics. A key limitation of the model is that it is only valid for a single set of initial conditions, i.e., grain size and density. Recent in situ sintering experiments suggest that densification follows nucleation-limited kinetics. A model for sintering can be formulated based on a thermodynamic energy balance between interfacial energy dissipation and work required to overcome the nucleation barrier. A feature of this model is that it inherently relates coarsening and densification, providing a basis for formulating a generalized master sintering curve that is not sensitive to initial conditions. This paper develops the model and demonstrates its practical application to several oxide systems, including ZnO, Al<sub>2</sub>O<sub>3</sub>, and Y<sub>2</sub>O<sub>3</sub>-doped tetragonal ZrO<sub>2</sub>.</div></div>","PeriodicalId":17408,"journal":{"name":"Journal of The European Ceramic Society","volume":"45 3","pages":"Article 116991"},"PeriodicalIF":5.8,"publicationDate":"2024-10-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142527702","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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