Synthesis and phase transition of negative thermal expansion materials Zr1−xLuxW2O8−y

Zr1−xLuxW2O8−y solid solutions were newly synthesized by a solid sate reaction method. X-ray diffraction (XRD) experiments from 90 to 560 K revealed that the solid solutions were of a single phase up to x = 0.04 and showed a negative thermal expansion. Order–disorder phase transition temperatures (Ttrs) and saturated order parameters (ηs) associated with WO4 orientational order were determined from the XRD results. The linear relationship between the normalized Ttrs and ηs obtained for Zr1−xMxW2O8−y (M = Sc, Y, In) in our previous study was also found for Zr1−xLuxW2O8−y. A heat capacity anomaly due to the order–disorder phase transition was detected for Zr0.96Lu0.04W2O8−y by a relaxation calorimeter. Ttrs of the solid solutions drastically decreased with increasing Lu content. The drastic suppression of Ttrs can be explained by the model assuming the existence of a local nano-region including the WO4 pairs having the orientational disorder.