Microstructures and Piezoelectric Properties of Microwave-Sintered Pb(Mn1/3Nb2/3)0.1Zr0.52Ti0.38O3 Ceramics

Abstract

In this work, we study the microstructural modifications and the electrical properties of Pb(Mn1/3Nb2/3)0.1Zr0.52Ti0.38O3 + 1.5 wt% PbO (PMNZT) ceramics processed using microwave sintering (MS) and conventional sintering (CS) techniques. Dielectric and piezoelectric properties were evaluated via an impedance/gain phase analyzer and the corresponding microstructures were examined using transmission electron microscopy (TEM). The experimental results imply that smaller grain size and less loss of PbO obtained for specimens using MS process. The MS specimens (1200°C-15 min) show the remanent polarization (Pr) of 24.1 μC/cm2, coercive field (Ec) of 15.2 kV/cm, dielectric constants (ϵr) of 432 and electromechanical coupling coefficient (kp) of 0.47, which are superior to CS specimens (1200°C-2 h) with Pr = 19.5 μC/cm2, Ec = 16.1 kV/cm, ϵr = 395 and kp = 0.45. The results revealed that the MS process shows capability of fabrication of good quality PMNZT ceramics with advantages of lowing process temperature and shorten process time. TEM investigations of MS specimens show that smaller grain size and simpler domain arrangements exist inside the specimens. From the energy aspect, the domain structure in piezoelectric ceramics below the temperature of a ferroelectric structural phase transformation is a result of energy minimization. Homogeneous elastic strain energy is reduced at the expense of domain boundary energy during the phase transformation. Density of domain boundaries, 71° (109°) domains in particular, depends on and increases with the grain size. Base on the above argument, therefore, CS specimens exhibit more complicated domain arrangements because they possess larger grain size than MS specimens do. The microstructural investigations suggest that the electrical property difference is intimately related to different sintering methods since the complicated domain arrangements could hinder domain moving and deteriorate electrical performance. In addition, the microstructural characteristics in both MS and CS specimens will be discussed further in the context.