Stability of (Ln0.8Ca0.1Ln′0.1)2Ti2O7-δ (Ln=Dy, Yb; Ln′=Ce, Tb) and (Tb0.9Ca0.1)2Ti2O7-δ pyrochlores under redox conditions

被引：5

作者：

Savvin, S. N. ^{[2
]}

Shlyakhtina, A. V. ^{[1
]}

Belov, D. A. ^{[3
]}

Ruiz-Morales, J. C. ^{[2
]}

Shcherbakova, L. G. ^{[1
]}

Nunez, P. ^{[2
]}

机构：

[1] Russian Acad Sci, NN Semenov Chem Phys Inst, Moscow 119991, Russia

[2] Univ La Laguna, Dept Inorgan Chem, Tenerife 38200, Spain

[3] Moscow MV Lomonosov State Univ, Dept Chem, Moscow 119991, Russia

来源：

SOLID STATE IONICS | 2012年 / 225卷

关键词：

Pyrochlore; Donor doping; High-temperature conductivity; Ionic conductivity; Solid electrolyte; Electronic conductivity; FT-IR SPECTRA; ELECTRICAL-CONDUCTIVITY; ELECTRONIC CONDUCTION; SM; CA; GD; FLUORITE; ZR; TI; DY;

D O I：

10.1016/j.ssi.2012.02.009

中图分类号：

O64 [物理化学（理论化学）、化学物理学];

学科分类号：

070304 ; 081704 ;

摘要：

The stability of (Ln(0.8)Ca(0.1)Ln'(0.1))(2)Ti2O7-delta(Ln=Dy, Yb; Ln'=Ce, Tb) pyrochlores under different redox conditions (air, dry and wet H-2) has been studied. The bulk conductivity of the terbium-containing materials is slightly higher under reducing conditions (5% H-2 + 95% Ar) than in air, reaching similar to 6 x 10(-2) and 2.5 x 10(-2) S/cm at 800 degrees C for (Yb0.8Ca0.1Tb0.1)(2)Ti2O7-delta and (Dy0.8Ca0.1Tb0.1)(2)Ti2O7-delta, respectively. In air-hydrogen-air cycles, the bulk conductivity returns to its original level in air: similar to 2 x 10(-2) and 1 x 10(-2) S/cm at 800 degrees C in (Yb0.8Ca0.1Tb0.1)(2)Ti2O7-delta and (Dy0.8Ca0.1Tb0.1)(2)Ti2O7-delta respectively. Exposure of (Dy0.8Ca0.1Tb0.1)(2)Ti2O7-delta to a flowing mixture of 5% H-2 and 95% Ar for 100 h slightly reduces its conductivity: from 0.029 to 0.023 S/cm at 900 degrees C. The cerium-containing materials (Yb0.8Ca0.1Tb0.1)(2)Ti2O7-delta and (Dy0.8Ca0.1Ce0.1)(2)Ti2O7-delta were found to be unstable under reducing conditions. The bulk conductivity of (Yb0.8Ca0.1Ce0.1)(2)Ti2O7-delta is practically independent on the atmosphere while the grain boundary conductivity increased from 5.6 x 10(-8) in air to similar to 1 x 10(-5) S/cm at 425 degrees C on reducing the sample in 5%H-2-Ar gas mixture. However, after two redox cycles air-5%H-2-Ar-air the sintered pellet of (Yb0.8Ca0.1Ce0.1)(2)Ti2O7-delta fractured whereas (Dy0.8Ca0.1Ce0.1)(2)Ti2O7-delta degraded immediately under reducing conditions. It was observed that the size mismatch between Ln and Ln cations strongly affects the bulk to grain boundary conductivity ratio in (Ln(0.8)Ca(0.1)Ln'(0.1))(2)Ti2O7-delta (Ln=Dy, Yb; Ln'=Ce, Tb) pyrochlores. (C) 2012 Elsevier B.V. All rights reserved.

引用

页码：457 / 463

页数：7

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