Phase transition and materials design of PbZrO3-based antiferroelectric ceramics

Abstract

The recent two decades witnessed a surging enthusiasm in searching for advanced functional materials, of which antiferroelectrics have gained much attention for many potential applications, especially for high-energy-density capacitors. The antiferroelectric-to-ferroelectric phase transformation process is at the heart of such applications. PbZrO3-based ceramics are still the main choice of materials due to their superb properties. In-situ transmission electron microscopy (TEM) is an advanced characterization tool for studying various nanoscale dynamic processes in real-time. External stress can influence the antiferroelectric-to-ferroelectric phase transformation. An in-situ heating TEM work in this dissertation elucidates the micromechanisms of the excellent pyroelectricity in a PbZrO3-based antiferroelectric with ZnO ceramic composite. The interaction between the antiferroelectric matrix and the second phase is observed to produce residual stresses and their impact on the ferroelectric → antiferroelectric phase transformation is directly revealed. The response of antiferroelectric with regard to electric field is a primary research interest in the antiferroelectric study. In this dissertation, an in-situ biasing TEM work on a PbZrO3-based ceramic reveals the ferroelectric phase nucleation and growth out of the antiferroelectric phase. The faceting behavior at the moving phase boundary during phase transition is observed in real space for the first time. For applications in the energy-storage capacitors, the electric hysteresis of the antiferroelectric-ferroelectric phase transition needs to be minimized for extended charge-discharge lifetime and enhanced energy efficiency. Guided by the concept of relaxor antiferroelectrics, a novel doping scheme, equal molar fraction co-doping of Li+ and Bi3+, is demonstrated in an antiferroelectric PbZrO3-based ceramic. Strong relaxor characteristics are imparted, and electric hysteresis is significantly suppressed and ultrahigh energy efficiency (94%) is realized.