Improvement of thermochromic property at low temperatures of CuMo0.94W0.06O4 by Zn substitution

Zinc-doped copper molybdenum oxide, Zn-doped CuMo0.94W0.06O4, was synthesized, and the effects of the Zn doping on the thermochromic property of CuMo0.94W0.06O4 were investigated at low temperatures. X-ray diffractometry and diffuse reflectance UV–Vis spectroscopy clarified that Zn doping for CuMo0.94W0.06O4 promoted the structural phase transition of the γ-phase to the α-phase of CuMo0.94W0.06O4 at low temperatures and Zn-doped CuMo0.94W0.06O4 exhibited a drastic color change in the temperature range of 30–70 °C. Differential scanning calorimetry also confirmed that Zn doping changed the phase transition temperature of CuMo0.94W0.06O4. Consequently, Cu1−xZnxMo0.94W0.06O4 with x = 0.01 exhibited a larger thermal change in the diffuse reflectance spectrum in the visible light range, compared with CuMo0.94W0.06O4. An appropriate Zn-doping ratio was effective for enhancing the thermochromic property of the CuMo0.94W0.06O4 pigment in the visible region in the temperature range of 30–70 °C.