Low temperature phase transition in zirconium-rich PZT ceramics

Abstract

Measurements of thermal expansion and complex Young's modulus in ferroelectric ceramics of zirconium-rich compositions and formula PbZr 1-x Ti x O 3 , x = 15.0-5.0%, and Pb 1-x/2 (Zr 1-x Ti x ) 1-y Nb y O 3 with x = 3.5-3.0%, y = 2.6% as a function of the temperature were performed. In composition with x = 5% dielectric measurements as a function of the temperature were also don The results of the measurements show anomalies in the studied characteristics at temperatures of 145°C(x=15%), 110°C(x = 5%), 35°C(x =3.5%) and 28°C(x=3%), apart of those of the ferro-paraelectric phase transition. The phase diagram indicates that, at room temperature, compositions with x<6% should be in the antiferroelectric phase with an orthorrombic structure and that with x=15% in the ferroelectric phase with rhomboedric structure. In the composition x =5% all the measurements show anomalies at 110°C in the first heating run, where the antiferroelectric phase changes to the ferroelectric phase of rhomboedric structure. In the cooling run the ferroelectric phase remains till 28°C. At this temperature the antiferroelectric phase is again obtained A large thermal hysteresis is present. The ferro- ferroelectric temperature phase transition of the composition with x=15% behaves according to the phase diagram and that with x=3.5% is quite far away of the phase diagram values, Explanations for these results are given.