Synthesis of nanostructured La2Zr2O7 by a non-alkoxide sol-gel method: From gel to crystalline powders

Nanocrystalline La2Zr2O7 powders of single prochlore phase were synthesized by a non-alkoxide sol-gel process. Homogeneous sol, free of precipitation, was prepared by addition of citric acid, polyethylene glycol and formamide to aqueous solutions of Zr4+ and La3+ inorganic salt precursors. We found that fluorite structure La2Zr2O7 was crystallized at 1000 degrees C, and then transformed to pyrochlore structure at 1200 degrees C. With further increase in temperature, the crystalline degree of pyrochlore La2Zr2O7 powders increased. The particle size of the as-prepared La2Zr2O7 powders at 1200 degrees C was about 80-200 nm. With temperature increase, sintering of La2Zr2O7 particles resulted in grain size growth. Mechanism of La2Zr2O7 nano-particles as function of temperature during heat treatment was analyzed. The density of the powders sintered at 1600 degrees C was 96.0% of the theoretical value, and thermal conductivity ranged from 0.65 to 0.85 W.m(-1).K-1, which was much lower than that of 7YSZ. (C) 2014 Elsevier Ltd. All rights reserved.