Interstitial oxide positions in oxygen-excess oxy-apatites |
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| Institution: | 1. School of Physics, University of Electronic Science and Technology of China, Chengdu, 611731, People''s Republic of China;2. Glasgow College, University of Electronic Science and Technology of China, Chengdu, 611731, People''s Republic of China;3. College of Physics, Taiyuan University of Technology, Taiyuan, 030024, People''s Republic of China;1. Guangdong Provincial Key Laboratory of New Drug Screening, School of Pharmaceutical Sciences, Southern Medical University, Guangzhou 510515, China;2. Guangxi Key Laboratory of Calcium Carbonate Resources Comprehensive Utilization, College of Materials and Environmental Engineering, Hezhou University, Hezhou 542899, China;3. State Key Laboratory Base of Eco-chemical Engineering, Laboratory of Inorganic Synthesis and Applied Chemistry, College of Chemistry and Molecular Engineering, Qingdao University of Science and Technology, Qingdao 266042, China;1. Department of Physics, Indian Institute of Technology Jodhpur, 342037, India;2. Materials Characterization Division, Solid State Physics Laboratory, New Delhi, 110054, India;3. Center for Solar Energy, Indian Institute of Technology Jodhpur, Rajasthan, 342037, India;1. College of Chemistry & Pharmacy, Northwest A&F University, Yangling, Shaanxi, 712100, PR China;2. College of Chemistry & Biology and Environmental Engineering, Xiangnan University, Chenzhou, Hunan, 423043, PR China;3. College of Materials and Chemical Engineering, Key Laboratory of Inorganic Nonmetallic Crystalline and Energy Conversion Materials, China Three Gorges University, Yichang, Hubei, 443002, PR China;4. Hunan Provincial Key Laboratory of Xiangnan Rare-Precious Metals Compounds Research and Application, Chenzhou, Hunan, 423043, PR China;1. Academic Area of Earth Sciences and Materials, Autonomous University of Hidalgo State, Road Pachuca-Tulancingo km 4.5, Mineral de la Reforma zip code 42184, Hidalgo, Mexico;2. Department of Metallurgical and Materials Engineering, ESIQIE, National Polytechnic Institute, UPALM, Zacatenco, Mexico City, zip code 07738, Mexico;3. Industrial Engineering Department, Technological Institute of Pachuca, Road México-Pachuca km. 87.5, Pachuca de Soto zip code 42080, Hidalgo, Mexico |
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| Abstract: | Several oxy-apatites materials, La8.65Sr1.35(Si6O24)O2.32, La8.65Sr1.35(Ge6O24)O2.32, La9Sr1(Si5.5Al0.5O24)O2.25, La9.67□0.33(Si5.5Al0.5O24)O2.25, La8.5Sr1.5(Si5.5Al0.5O24)O2 and La9.5□0.5(Si5.5Al0.5O24)O2 have been prepared as crystalline phases. The impedance study showed that all samples are oxide ion conductors and their conductivities are similar to those previously reported for related oxy-apatites. A thorough study on the oxygen sublattices for oxygen excess samples has been carried out using neutron powder diffraction data by the Rietveld method. The structural study shows the presence of interstitial oxide anions close to the periphery apatite channels. However, the interstitial oxide position in cation stoichiometric silicates, f. i. La8.65Sr1.35(Si6O24)O2.32, is different from that in germanates, f. i. La8.65Sr1.35(Ge6O24)O2.32. This is likely due to the different structural flexibility of the two tetrahedral groups and it explains the previously reported evidence of higher oxygen contents for germanates oxy-apatites. The structural characteristics of these oxide anion conductors are discussed. |
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