Diffuse phase transition in mechanically activated (Pb < inf > 1−x < /inf > La < inf > x < /inf > )(Zr < inf > 0.60 < /inf > Ti < inf > 0.40 < /inf > )O < inf > 3 < /inf > electro-ceramics

Abstract

In this paper, the dielectric properties of (Pb1−xLax)(Zr0.60Ti0.40)O3 (referred to from now on as PLZT x/60/40) ceramics were investigated for the optimization of La substitution at the A-site of PZT ceramics. The PLZT x/60/40 ceramic powders were synthesized by mechanical activation and compaction of these fine scale nano powders was done using cold isostatic pressing. The present study suggests that lanthanum substitution affects the nature of the ferroelectric phase transition of PZT showing a deviation from normal to the diffuse type phase transition (DPT). The parameters of this DPT, such as the degree of deviation from Curie–Weiss law (ΔTm), diffuseness empirical parameters γ and ΔTdiff were calculated for different compositions of PLZT ceramics at 1 kHz. The large value of γ (1 < γ < 2) and ΔTdiff confirms the deviation from normal phase transition and the high degree of disorderliness in the material. It is also found that the Curie temperature Tc and maximum dielectric constant εmax both decrease with increasing La3+ content. The maximum value of dielectric constant for the PLZT 8/60/40 ceramics was found to be ~1975.