Synthesis of zirconium tungstate-zirconia core-shell composite particles

In this work, ZrW(2)O(8)-ZrO(2) core-shell composite particles were synthesized. ZrW(2)O(8) that was used in the core is a material with negative coefficient of thermal expansion, and it was synthesized from a high-pH precursor based on use of tungstic acid and zirconium acetate. Shell layer was composed of ZrO(2) nanocrystallites and precipitated from an aqueous solution by urea hydrolysis. While volume of the shell was effectively controlled by the initial zirconium ion concentration in the solutions, the rate of precipitation was a function of the ratio of initial concentrations of urea to zirconium ions. It is hypothesized that isolation of the ZrW(2)O(8) within a layer of ZrO(2), will be a key element in solving problems associated with reactivity of ZrW(2)O(8) towards other components in sintering of ceramic-ceramic composites with tuned or zero thermal expansion coefficient. (C) 2011 Elsevier Ltd. All rights reserved,