Thermal Dilatation in Pb(Zn_1/3Nb_2/3)O₃Crystal

The temperature dependence of the cell dimension of Pb(Zn_1/3Nb_2/3)0₃. crystal was investigated in the temperature range between liquid nitrogen temperature and 400°C by using an X-ray diffractometer and a thermal dilatometer of differential transformer type. The latticeconstant a increases with increasing temperature and the rhombohedral angle α approaches 90° at about 150°C. An anomaly in thermal dilatation was observed over a wide range of temperatures, corresponding to a diffuse transition from ferroelectric to paraelectric phase. The linear thermal expansion coefficient decreases with increasing temperature in the ferroelectric phase, reaches a minimum at about 120°C, and then gradually increases to a constant value(10.0×10^-6K^-1)in the higher temperature region.