Pub Date : 2023-10-01DOI: 10.2109/jcersj2.131.h10-1
{"title":"Cover","authors":"","doi":"10.2109/jcersj2.131.h10-1","DOIUrl":"https://doi.org/10.2109/jcersj2.131.h10-1","url":null,"abstract":"","PeriodicalId":17246,"journal":{"name":"Journal of the Ceramic Society of Japan","volume":"18 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135372992","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Lieyang Li, Hiroshi Masuda, Hidenobu Murata, Atsushi Nakahira, Hidehiro Yoshida
Field-assisted sintering technique (FAST) and flash sintering experiments were conducted on hydroxyapatite (HAp) ceramics to attaining highly densified HAp body with uniform microstructure. FAST region, in which the densification was gradually accelerated, was observed from 800 °C under all fields examined. Under the field strength beyond 1000 V·cm−1, the FAST followed by flash sintering took place. The phase decomposition can be effectively suppressed by the FAST/flash sintering. During the FAST region, microstructure remained uniform and the relative density of 94 % was achieved. By the flash sintering at 1000 V·cm−1, the relative density of 97 % was achieved, but inhomogeneous microstructure appeared. By conducting controlled current rate sintering, the densification of the HAp with homogeneous microstructure was attained. The avoidance of current surge and localized current path through the specimen was crucial to attain the uniform, densified microstructure in the HAp ceramics.
{"title":"Densification of hydroxyapatite ceramics by field-assisted sintering followed by controlled current ramp sintering","authors":"Lieyang Li, Hiroshi Masuda, Hidenobu Murata, Atsushi Nakahira, Hidehiro Yoshida","doi":"10.2109/jcersj2.23074","DOIUrl":"https://doi.org/10.2109/jcersj2.23074","url":null,"abstract":"Field-assisted sintering technique (FAST) and flash sintering experiments were conducted on hydroxyapatite (HAp) ceramics to attaining highly densified HAp body with uniform microstructure. FAST region, in which the densification was gradually accelerated, was observed from 800 °C under all fields examined. Under the field strength beyond 1000 V·cm−1, the FAST followed by flash sintering took place. The phase decomposition can be effectively suppressed by the FAST/flash sintering. During the FAST region, microstructure remained uniform and the relative density of 94 % was achieved. By the flash sintering at 1000 V·cm−1, the relative density of 97 % was achieved, but inhomogeneous microstructure appeared. By conducting controlled current rate sintering, the densification of the HAp with homogeneous microstructure was attained. The avoidance of current surge and localized current path through the specimen was crucial to attain the uniform, densified microstructure in the HAp ceramics.","PeriodicalId":17246,"journal":{"name":"Journal of the Ceramic Society of Japan","volume":"19 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135372634","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Takuma Noda, Hanseul Kim, Kenta Watanabe, Kota Suzuki, Naoki Matsui, Ryoji Kanno, Masaaki Hirayama
The reaction distribution in the composite cathode of an all-solid-state battery (ASSB) was directly tracked by in situ scanning electron microscopy (SEM) combined with energy dispersive X-ray spectroscopy (EDX). Contact between an electrode active material and a solid electrolyte is important for improving the properties of ASSBs as a promising next-generation battery. An in situ analysis is significant for establishing strategies to obtain sufficient contact areas between the active material and solid electrolyte particles. SEM-EDX has the advantages of in-situ measurement in spatial/time resolution, non-destruction, and versatility. We investigated the sensitivity of EDX to the Na signal and distinguishable distance to ensure sufficient spatial/time resolution. The acceleration voltage of 5 kV for the electron beam provided the highest sensitivity to the Na signal among all acceleration voltages. The distinguishable distance decreased with increasing magnification owing to the decrease in pixel size. Cross-sectional SEM-EDX images of the TiS2–Na3PS4/Na3PS4/Na–Sn cell were collected during charge/discharge. The time variation of Na signal intensity confirms the deintercalation of Na+ in the TiS2–Na3PS4 cathode layer. Moreover, intercalation on the solid electrolyte side proceeded faster than that on the current collector side. This was because the rate-determining step was ionic conductivity rather than electronic conductivity based on the difference between ionic and electronic conductivities. Ex situ observations detected only a uniform distribution in the composite after Na+ diffusion had relaxed. Operando SEM-EDX is a new tool to directly explore the intermediate conditions of electrode materials under ASSB operation.
{"title":"Direct tracking of reaction distribution in an all-solid-state battery using operando scanning electron microscopy with energy dispersive X-ray spectroscopy","authors":"Takuma Noda, Hanseul Kim, Kenta Watanabe, Kota Suzuki, Naoki Matsui, Ryoji Kanno, Masaaki Hirayama","doi":"10.2109/jcersj2.23067","DOIUrl":"https://doi.org/10.2109/jcersj2.23067","url":null,"abstract":"The reaction distribution in the composite cathode of an all-solid-state battery (ASSB) was directly tracked by in situ scanning electron microscopy (SEM) combined with energy dispersive X-ray spectroscopy (EDX). Contact between an electrode active material and a solid electrolyte is important for improving the properties of ASSBs as a promising next-generation battery. An in situ analysis is significant for establishing strategies to obtain sufficient contact areas between the active material and solid electrolyte particles. SEM-EDX has the advantages of in-situ measurement in spatial/time resolution, non-destruction, and versatility. We investigated the sensitivity of EDX to the Na signal and distinguishable distance to ensure sufficient spatial/time resolution. The acceleration voltage of 5 kV for the electron beam provided the highest sensitivity to the Na signal among all acceleration voltages. The distinguishable distance decreased with increasing magnification owing to the decrease in pixel size. Cross-sectional SEM-EDX images of the TiS2–Na3PS4/Na3PS4/Na–Sn cell were collected during charge/discharge. The time variation of Na signal intensity confirms the deintercalation of Na+ in the TiS2–Na3PS4 cathode layer. Moreover, intercalation on the solid electrolyte side proceeded faster than that on the current collector side. This was because the rate-determining step was ionic conductivity rather than electronic conductivity based on the difference between ionic and electronic conductivities. Ex situ observations detected only a uniform distribution in the composite after Na+ diffusion had relaxed. Operando SEM-EDX is a new tool to directly explore the intermediate conditions of electrode materials under ASSB operation.","PeriodicalId":17246,"journal":{"name":"Journal of the Ceramic Society of Japan","volume":"17 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135372804","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
A Fe-modified Na-P1 type artificial zeolite (Fe-P1) was prepared by mixing with the synthesized zeolite powder using chemical reagents and FeCl3 solution. The anion exchange capacity was generated by the iron hydroxyl group on the zeolite surface. Although the intensity of the X-ray diffraction (XRD) peaks for the zeolite phase decreased with an increase in the concentration of the mixed FeCl3 solution, the anion exchange ability for the phosphate was improved due to the increase in the surface area. The Fe-P1 zeolite showed a high selectivity for the anions of phosphoric acid and arsenic acid. The anion adsorption capacity was significantly increased under the acidic condition (pH 5) of the solution. Acidic treatment of the Fe-P1 zeolite was also effective for the anion adsorption.
{"title":"Anion adsorption capacity from the iron hydroxyl group of Fe-modified Na-P1 type zeolite","authors":"Hiromichi Aono, Yasutaka Matsumoto, Yoshiteru Itagaki","doi":"10.2109/jcersj2.23023","DOIUrl":"https://doi.org/10.2109/jcersj2.23023","url":null,"abstract":"A Fe-modified Na-P1 type artificial zeolite (Fe-P1) was prepared by mixing with the synthesized zeolite powder using chemical reagents and FeCl3 solution. The anion exchange capacity was generated by the iron hydroxyl group on the zeolite surface. Although the intensity of the X-ray diffraction (XRD) peaks for the zeolite phase decreased with an increase in the concentration of the mixed FeCl3 solution, the anion exchange ability for the phosphate was improved due to the increase in the surface area. The Fe-P1 zeolite showed a high selectivity for the anions of phosphoric acid and arsenic acid. The anion adsorption capacity was significantly increased under the acidic condition (pH 5) of the solution. Acidic treatment of the Fe-P1 zeolite was also effective for the anion adsorption.","PeriodicalId":17246,"journal":{"name":"Journal of the Ceramic Society of Japan","volume":"42 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135372978","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Mass transfer along a grain boundary (GB) in a Σ31 alumina bicrystal wafer was investigated using the oxygen permeation technique with 18O2 at 1873 K, where oxide ions migrated along the GB from the high oxygen partial pressure [PO2(hi)] surface to the low oxygen partial pressure [PO2(lo)] surface, and aluminum ions moved concurrently in the opposite direction. It was found that the application of an oxygen potential gradient more strongly inhibited the migration of oxide ions along the GB within a shorter distance from the PO2(hi) surface, compared with the case of the polycrystalline alumina. Moreover, in the case of high-angle GBs like Σ31 GB, as the GB gets close to the surface, the GB plane undergoes more pronounced lateral movement in the transverse direction. The GB movement is thought to be due to annihilation of aluminum vacancies stagnating in a nonequilibrium state near the surface.
{"title":"Effect of oxygen potential gradient on mass transfer along grain boundary in alumina bicrystal","authors":"Tsuneaki Matsudaira, Takafumi Ogawa, Miyuki Takeuchi, Jiake Wei, Bin Feng, Naoya Shibata, Yuichi Ikuhara, Satoshi Kitaoka","doi":"10.2109/jcersj2.23073","DOIUrl":"https://doi.org/10.2109/jcersj2.23073","url":null,"abstract":"Mass transfer along a grain boundary (GB) in a Σ31 alumina bicrystal wafer was investigated using the oxygen permeation technique with 18O2 at 1873 K, where oxide ions migrated along the GB from the high oxygen partial pressure [PO2(hi)] surface to the low oxygen partial pressure [PO2(lo)] surface, and aluminum ions moved concurrently in the opposite direction. It was found that the application of an oxygen potential gradient more strongly inhibited the migration of oxide ions along the GB within a shorter distance from the PO2(hi) surface, compared with the case of the polycrystalline alumina. Moreover, in the case of high-angle GBs like Σ31 GB, as the GB gets close to the surface, the GB plane undergoes more pronounced lateral movement in the transverse direction. The GB movement is thought to be due to annihilation of aluminum vacancies stagnating in a nonequilibrium state near the surface.","PeriodicalId":17246,"journal":{"name":"Journal of the Ceramic Society of Japan","volume":"18 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135372980","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
In the present study, tracer and conductivity diffusion coefficients (D* and Dσ), and the Haven ratio HR defined as D*/Dσ have been theoretically estimated in proton-conducting perovskite ceramics using the kinetic Monte Carlo (KMC) simulations. D* was estimated from the mean square displacement of protons in the equilibrium state by the ordinary KMC simulations, while Dσ was estimated from the drift velocity of protons in the non-equilibrium KMC simulations with an applied electric field. Taking proton-conducting yttrium-doped barium zirconate (BaZr1−xYxO3, 0 < x ≤ 0.3) with the cubic perovskite structure as a model system, the D*, Dσ, and HR of protons were estimated at intermediate temperatures. The estimated HR are almost unity in the range of 0.99 and 1.04, indicating that the conventional mobility and conductivity estimation using the tracer diffusion coefficient D* through the Nernst-Einstein equation is reasonable approximation for this model system. Exactly, the estimated HR are slightly higher than unity in the case of high doping levels particularly at low temperatures, which is an opposite trend to the general HR (≤ 1) in solid state ionic conductors.
{"title":"A kinetic Monte Carlo study for Haven ratio of proton transport in perovskite ceramics","authors":"Kazuaki Toyoura, Tsukasa Takahashi","doi":"10.2109/jcersj2.23020","DOIUrl":"https://doi.org/10.2109/jcersj2.23020","url":null,"abstract":"In the present study, tracer and conductivity diffusion coefficients (D* and Dσ), and the Haven ratio HR defined as D*/Dσ have been theoretically estimated in proton-conducting perovskite ceramics using the kinetic Monte Carlo (KMC) simulations. D* was estimated from the mean square displacement of protons in the equilibrium state by the ordinary KMC simulations, while Dσ was estimated from the drift velocity of protons in the non-equilibrium KMC simulations with an applied electric field. Taking proton-conducting yttrium-doped barium zirconate (BaZr1−xYxO3, 0 < x ≤ 0.3) with the cubic perovskite structure as a model system, the D*, Dσ, and HR of protons were estimated at intermediate temperatures. The estimated HR are almost unity in the range of 0.99 and 1.04, indicating that the conventional mobility and conductivity estimation using the tracer diffusion coefficient D* through the Nernst-Einstein equation is reasonable approximation for this model system. Exactly, the estimated HR are slightly higher than unity in the case of high doping levels particularly at low temperatures, which is an opposite trend to the general HR (≤ 1) in solid state ionic conductors.","PeriodicalId":17246,"journal":{"name":"Journal of the Ceramic Society of Japan","volume":"15 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135372991","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Ayaka Endo, Ryosuke Nitta, Yuta Kubota, Nobuhiro Matsushita
Crystalline Cu2O films were fabricated via the spin-spray method at substrate temperature (Ts) below 90 °C, without the post heat treatment. Grain size, crystal orientation and optical band gap controls of Cu2O films were achieved by changing Ts. The film orientation was delicately tuned in sequence from {111} to {200} with Ts increasing from 50 to 90 °C. The Cu2O film fabricated at Ts of 70 °C had a film thickness of 1.19 µm and consisted of a columnar structure with an average diameter size of 0.8 µm. In contrast, the films fabricated at Ts of 90 °C were composed of nanoparticles with diameters less than 0.1 µm. It was observed that a smaller grain size on the film surface corresponded to a wider optical band gap. Notably, the film fabricated at Ts of 50 °C exhibited a relatively wide band gap of 2.97 eV due to the quantum size effect.
{"title":"Crystallized Cu<sub>2</sub>O films fabricated at low substrate temperature of 50–90 °C by spin-spray method","authors":"Ayaka Endo, Ryosuke Nitta, Yuta Kubota, Nobuhiro Matsushita","doi":"10.2109/jcersj2.23034","DOIUrl":"https://doi.org/10.2109/jcersj2.23034","url":null,"abstract":"Crystalline Cu2O films were fabricated via the spin-spray method at substrate temperature (Ts) below 90 °C, without the post heat treatment. Grain size, crystal orientation and optical band gap controls of Cu2O films were achieved by changing Ts. The film orientation was delicately tuned in sequence from {111} to {200} with Ts increasing from 50 to 90 °C. The Cu2O film fabricated at Ts of 70 °C had a film thickness of 1.19 µm and consisted of a columnar structure with an average diameter size of 0.8 µm. In contrast, the films fabricated at Ts of 90 °C were composed of nanoparticles with diameters less than 0.1 µm. It was observed that a smaller grain size on the film surface corresponded to a wider optical band gap. Notably, the film fabricated at Ts of 50 °C exhibited a relatively wide band gap of 2.97 eV due to the quantum size effect.","PeriodicalId":17246,"journal":{"name":"Journal of the Ceramic Society of Japan","volume":"4 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135372638","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Alkaline earth (AE) metal-alloyed SnS films with a bandgap of 1.8 eV were demonstrated to us promising for their use in widegap photovoltaic absorbers by forming a p-n junction with an n-type CdS layer. The Ba-alloyed-SnS film exhibited the highest efficiency among the three types of AE-alloyed SnS films (barium, calcium, and strontium alloyed-SnS films). Electricity generation by the formation of the junction of p-AE-alloyed SnS/n-CdS indicates the possibility of realizing Si-based tandem solar cells.
{"title":"Fabrication of the bandgap-tuned alkaline earth-alloyed SnS solar cell","authors":"Fumio Kawamura, Yelim Song, Hidenobu Murata, Hitoshi Tampo, Takehiko Nagai, Takashi Koida, Jaeeun Jeon, Masataka Imura, Naoomi Yamada","doi":"10.2109/jcersj2.22162","DOIUrl":"https://doi.org/10.2109/jcersj2.22162","url":null,"abstract":"Alkaline earth (AE) metal-alloyed SnS films with a bandgap of 1.8 eV were demonstrated to us promising for their use in widegap photovoltaic absorbers by forming a p-n junction with an n-type CdS layer. The Ba-alloyed-SnS film exhibited the highest efficiency among the three types of AE-alloyed SnS films (barium, calcium, and strontium alloyed-SnS films). Electricity generation by the formation of the junction of p-AE-alloyed SnS/n-CdS indicates the possibility of realizing Si-based tandem solar cells.","PeriodicalId":17246,"journal":{"name":"Journal of the Ceramic Society of Japan","volume":"29 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135372808","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Bin Feng, Sena Hoshino, Bin Miao, Jiake Wei, Yu Ogura, Atsutomo Nakamura, Eita Tochigi, Katsuyuki Matsunaga, Yuichi Ikuhara, Naoya Shibata
Mobility of dislocations in compound semiconductor materials can be changed by light illumination because the core structure of dislocations is supposed to be reconstructed by photoexcited carriers. However, the atomic structure of such dislocation cores has not been observed and is still poorly understood. In this study, we introduced dislocations in ZnS, one of the typical II–VI type compound semiconductors, by deformation under darkness, and investigated the atomic structure of the dislocation cores using scanning transmission electron microscopy (STEM) combined with theoretical calculations. Direct observation of the Zn core partial dislocation revealed that its atomic structure is in good agreement with the theoretically predicted dislocation core without electron trapping. Moreover, the dislocations were observed to move along a slip plane during the observation. These results indicate that the electron-trap-free dislocation is mobile and could be the origin of plasticity in the dark.
{"title":"Direct observation of intrinsic core structure of a partial dislocation in ZnS","authors":"Bin Feng, Sena Hoshino, Bin Miao, Jiake Wei, Yu Ogura, Atsutomo Nakamura, Eita Tochigi, Katsuyuki Matsunaga, Yuichi Ikuhara, Naoya Shibata","doi":"10.2109/jcersj2.23065","DOIUrl":"https://doi.org/10.2109/jcersj2.23065","url":null,"abstract":"Mobility of dislocations in compound semiconductor materials can be changed by light illumination because the core structure of dislocations is supposed to be reconstructed by photoexcited carriers. However, the atomic structure of such dislocation cores has not been observed and is still poorly understood. In this study, we introduced dislocations in ZnS, one of the typical II–VI type compound semiconductors, by deformation under darkness, and investigated the atomic structure of the dislocation cores using scanning transmission electron microscopy (STEM) combined with theoretical calculations. Direct observation of the Zn core partial dislocation revealed that its atomic structure is in good agreement with the theoretically predicted dislocation core without electron trapping. Moreover, the dislocations were observed to move along a slip plane during the observation. These results indicate that the electron-trap-free dislocation is mobile and could be the origin of plasticity in the dark.","PeriodicalId":17246,"journal":{"name":"Journal of the Ceramic Society of Japan","volume":"35 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135372803","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Artificial-neural-network (ANN) interatomic potentials for Al–Y–O and Al–Hf–O systems are constructed using density-function-theory (DFT) data and combined with Monte Carlo (MC) simulations in order to predict Y and Hf segregation behavior at the ∑7(4510)/[0001] grain boundary (GB) in α-Al2O3. The ANN potentials are demonstrated to accurately predict preferential substitutional sites of not only an isolated but also multiple dopant ions. This enables us to circumvent DFT calculations for MC trial moves, thereby greatly reducing computational cost. There is a tendency that both Y and Hf ions substitute for 6-fold Al ions with elongated Al–O bonds at the GB and have coordination numbers greater than 6 after structural relaxation. This may suggest that even at the GB, Y and Hf ions prefer atomic environments in Y- and Hf-containing oxides with 7- and 8-fold coordination. Furthermore, effects of dopant species and concentrations on band-gap reduction at the GB are elucidated by analyzing partial density of states for the dopant-segregated GBs. The ANN-MC method with DFT analysis will pave the way for systematically determining atomic and electronic structures of GBs involving dopants, as demonstrated in this work.
{"title":"Grain boundary segregation of Y and Hf dopants in α-Al<sub>2</sub>O<sub>3</sub>: A Monte Carlo simulation with artificial-neural-network potential and density-functional-theory calculation","authors":"Tatsuya Yokoi, Akihiro Hamajima, Yu Ogura, Katsuyuki Matsunaga","doi":"10.2109/jcersj2.23044","DOIUrl":"https://doi.org/10.2109/jcersj2.23044","url":null,"abstract":"Artificial-neural-network (ANN) interatomic potentials for Al–Y–O and Al–Hf–O systems are constructed using density-function-theory (DFT) data and combined with Monte Carlo (MC) simulations in order to predict Y and Hf segregation behavior at the ∑7(4510)/[0001] grain boundary (GB) in α-Al2O3. The ANN potentials are demonstrated to accurately predict preferential substitutional sites of not only an isolated but also multiple dopant ions. This enables us to circumvent DFT calculations for MC trial moves, thereby greatly reducing computational cost. There is a tendency that both Y and Hf ions substitute for 6-fold Al ions with elongated Al–O bonds at the GB and have coordination numbers greater than 6 after structural relaxation. This may suggest that even at the GB, Y and Hf ions prefer atomic environments in Y- and Hf-containing oxides with 7- and 8-fold coordination. Furthermore, effects of dopant species and concentrations on band-gap reduction at the GB are elucidated by analyzing partial density of states for the dopant-segregated GBs. The ANN-MC method with DFT analysis will pave the way for systematically determining atomic and electronic structures of GBs involving dopants, as demonstrated in this work.","PeriodicalId":17246,"journal":{"name":"Journal of the Ceramic Society of Japan","volume":"39 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135372986","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"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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