Synthesis and Characterization of a New Family of Mixed Oxide−Proton Conductors Based on Tristrontium Oxysilicate

详细信息    查看全文

• 作者：Jos&#xe9 ; M. Porras-V&#xe1 ; zquez ; Enrique R. Losilla ; Laura Leó ; n-Reina ; Mar&#xed ; a Mart&#xed ; nez-Lara ; Miguel A. G. Aranda
• 刊名：Chemistry of Materials
• 出版年：2008
• 出版时间：March 11, 2008
• 年：2008
• 卷：20
• 期：5
• 页码：2026 - 2034
• 全文大小：440K
• 年卷期：v.20,no.5(March 11, 2008)
• ISSN：1520-5002

文摘

A new Sr₃(Si_1−xAl_xO₄)O_1−x/2□_x/2 (0.0 ≤ x ≤ 0.2) oxysilicate series has been prepared, existing as a single phase for x ≤ 0.11. The evolution of the cell parameters was smooth along the series. The crystal structure of Sr₃(Si_0.9Al_0.1O₄)O_0.95□_0.05 was determined from neutron powder diffraction data at room temperature. This compound crystallizes in the P4/ncc space group, Z = 4, with a = 6.9427(1) Å, c = 10.7992(1) Å, and V = 520.53(1) ų. The Rietveld R values were R_WP = 2.54% and R_F = 1.33%. The Si⁴⁺/Al³⁺ aliovalent substitution is accompanied by oxygen vacancies for charge compensation. The crystal structure is described, as is a possible pathway for the “loosely bound” oxide anions that justifies the observed oxygen conductivity. Impedance data showed that the overall conductivity increased by more than 2 orders of magnitude from Sr₃(SiO₄)O to Sr₃(Si_0.89Al_0.11O₄)O_0.945□_0.055. Further electrochemical characterization under various atmospheres (dry air, wet air, dry 5% H₂ in Ar, and wet 5% H₂ in Ar) and impedance data as a function of the oxygen partial pressure indicated that there was a significant proton contribution to the overall conductivity. The oxide ion transference numbers, determined using a modified electromotive force method, ranged from 0.98 to 0.95 under strong reducing conditions. A large p-type electronic contribution was also observed for Sr₃(Si_0.89Al_0.11O₄)O_0.945□_0.055 under oxidizing conditions, decreasing the oxide ion transference number to ~0.01 at 1173 K.