Defect formation and transport in La0.95Ni0.5Ti0.5O3−δ
- 作者：S.O. Yakovlev ; V.V. Kharton ; E.N. Naumovich ; J. Zekonyte ; V. Zaporojtchenko ; A.V. Kovalevsky ; A.A. Yaremchenko ; J.R. Frade
- 关键词：Lanthanum nickelate-titanate ; A-site deficiency ; Defect association ; Oxygen ionic conductivity ; Hole transport ; Atomistic modelling ; Thermal expansion
- 刊名：Solid State Sciences
- 出版年：2006
- 期刊代码：98_12932558
- 类别：ch
- 出版时间：November 2006
- 卷：8
- 期：11
- 页码：1302-1311
- 文件大小：570 K
摘要
Deficiency in the A sublattice of orthorhombic perovskite-type La1−xNi0.5Ti0.5O3−δ, with maximum at ve&_udi=B6W6W-4M4KR81-3&_mathId=mml10&_user=10&_cdi=6609&_rdoc=7&_acct=C000050221&_version=1&_userid=10&md5=fe55671dce60214f4d09a8158d1add3f" title="Click to view the MathML source">x=0.07–0.08, is compensated by the formation of trivalent nickel and oxygen vacancies. The atomistic computer simulations showed that these defects are trapped near the A-site cation vacancies, resulting in the stabilization of Ni3+ cations and low electronic and oxygen-ionic transport. The average thermal expansion coefficient of La0.95Ni0.5Ti0.5O3−δ ceramics, calculated from dilatometric data in air, increases from at 300–800 K to at 1300–1500 K. The data on Seebeck coefficient and total conductivity, predominantly p-type electronic, suggest a broadband mechanism of hole transport. The activation energies for the hole and ionic conductivities are 89 and 430 kJ/mol, respectively. The oxygen ion transference numbers determined by the faradaic efficiency measurements in air, vary in the range ve&_udi=B6W6W-4M4KR81-3&_mathId=mml13&_user=10&_cdi=6609&_rdoc=7&_acct=C000050221&_version=1&_userid=10&md5=dc85e79018ad2e21637cbdbf5d59ce5e" title="Click to view the MathML source">9.5×10−5–ve&_udi=B6W6W-4M4KR81-3&_mathId=mml14&_user=10&_cdi=6609&_rdoc=7&_acct=C000050221&_version=1&_userid=10&md5=19f0c3e93c9cac1ddccf10f49b4938be" title="Click to view the MathML source">8.1×10−4 at 1173–1248 K, increasing with temperature. Reducing oxygen partial pressure leads to a moderate decrease of the conductivity, followed by phase decomposition in the ve&_udi=B6W6W-4M4KR81-3&_mathId=mml15&_user=10&_cdi=6609&_rdoc=7&_acct=C000050221&_version=1&_userid=10&md5=147274f4263e7fb1a7df2ec92272c960" title="Click to view the MathML source">p(O2) range ve&_udi=B6W6W-4M4KR81-3&_mathId=mml16&_user=10&_cdi=6609&_rdoc=7&_acct=C000050221&_version=1&_userid=10&md5=409f7738a1b1cbf95accabba4e2b1806" title="Click to view the MathML source">9×10−11 to at 1073–1223 K. The low-ve&_udi=B6W6W-4M4KR81-3&_mathId=mml18&_user=10&_cdi=6609&_rdoc=7&_acct=C000050221&_version=1&_userid=10&md5=f9c6d6dfdb7ec8ef39df7ad38ce9fe5a" title="Click to view the MathML source">p(O2) stability limit of La0.95Ni0.5Ti0.5O3−δ perovskite was found between that of La3Ni2O7 and Ni/NiO boundary.