Synthesis of negative thermal expansion materials ZrW_(2-x)Mo_xO_8 (0<=x<=2) using hydrothermal method

摘要

Negative thermal expansion materials ZrW_(2-x)Mo_xO_8 (0<= x<=2) have been successfully synthesized by the reaction of a mixture of ammonium tungstate and ammonium molybdate with zirconium oxynitrate using a hydrothermal method. Effect of substituted ion Mo on the microstructure, alpha-to-beta and cubic to trigonal phase transition in resulting ZrW_(2-x)Mo_xO_8 powders was examined by the XRD experiments. It was found that the structural phase transition temperature decreased slightly with increasing substituted content. The cubic to trigonal phase transition was also influenced by substituted content. The resulting products decomposed to WO_3/MoO_3 and ZrO_2 as temperature increasing when x<=0.5 and while x>0.5, the cubic phase transited to trigonal phase. The effect of substituted Mo on the morphology of resulting products was also investigated by SEM experiments.