A Temperature Responsive Copper Molybdate Polymorph Mixture Near to Water Boiling Point by a Simple Cryogenic Quenching Route

Smart temperature responsive inorganic materials in accessible temperature ranges open up new positions in the technology. Herein, we present for the first time a CuMoO4 polymorph mixture prepared by a simple cryogenic quenching approach, which offers a fast temperature response close to water boiling temperature for use as a permanent temperature recorder. The new cryogenic quenching technique initiates the formation of a unique polymorph mixture of a deep brown color with a non-uniform combination of γ and α-CuMoO4, with the γ phase confined to the outer region of α-CuMoO4, which has been prepared by conventional solid-state synthesis. In situ structural analysis and refinement results confirm the presence of CuMoO4 α and γ polymorphs, in which the amount of γ polymorph decreases and that of the α phase increases with temperature, accounting for the irreversible thermochromic behavior. The thermal analysis reveals that the polymorph mixture exhibits a fast response with the color changing from deep brow...