Synthesis of zirconium tungstate–zirconia core–shell composite particles

[Display omitted] ► ZrW 2O 8–ZrO 2 core–shell particles to offer solutions for sintering problems. ► Core synthesis by a precursor based on tungstic acid and zirconium acetate. ► Shell phase by urea hydrolysis in the presence of zirconium ions. ► [Urea]/[ZrOCl 2] ratio controls the rate of shell precursor precipitation. In this work, ZrW 2O 8–ZrO 2 core–shell composite particles were synthesized. ZrW 2O 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 2O 8 within a layer of ZrO 2, will be a key element in solving problems associated with reactivity of ZrW 2O 8 towards other components in sintering of ceramic–ceramic composites with tuned or zero thermal expansion coefficient.