Defects and Lattice Instability in Doped Lead-Based Perovskite Antiferroelectrics: Revisited

Dariusz Kajewski

doi:10.3390/cryst10060501

Abstract

This paper is a summary of earlier results that have been completed with recent investigations on the nature and sequence of phase transitions evolving in the antiferroelectric PbZrO3 single crystals doped with niobium and Pb(Zr0.70Ti0.30)O3 ceramics doped with different concentration of Bi2O3. It was found that these crystals undergo new phase transitions never observed before. To investigate all phase transitions, different experimental methods were used to characterize the crystal properties. Temperature and time dependencies have been tentatively measured in a wide range, including a region above Tc, where precursor dynamics is observed in the form of non-centrosymmetric regions existing locally in crystal lattices. Also, coexistence of antiferroelectric phase and one of the intermediate phases could be observed in a wide temperature range. The phase transition mechanism in PbZrO3 is discussed, taking into account the local breaking of the crystal symmetry above Tc and the defects of crystal lattices, i.e., those generated during crystal growth, and intentionally introduced by preheating in a vacuum or doping with hetero-valent dopant.

Highlights

Ferroelectrics and antiferroelectrics with perovskite structure which contain oxygen octahedrons are of great interest to scientists because of their numerous applications, and because of their versatile properties
The results presented in this report were obtained using the following experimental methods:
The summary can be divided into four main sections: 1. The effect of defects on phase transitions in pure PbZrO3 crystals [31]

Summary

Introduction

Ferroelectrics and antiferroelectrics with perovskite structure which contain oxygen octahedrons are of great interest to scientists because of their numerous applications, and because of their versatile properties. Many of them have been known for over 60 years and many theoretical and experimental works have already been reported, there is a range of newly discovered phenomena that remain unknown They concern mainly lattice dynamics and type-of-phase transitions, i.e., whether they are of the order–disorder or displacement type [1]. With the lowering of temperature, these regions increase in volume and eventually merge into the ferroelectric state below Tc [10]. Such scenario explains well the surprising occurrence of birefringence in BaTiO3 single crystals above Tc , i.e., in the centrosymmetric phase that excludes birefringence altogether [11]

Methods

Results

Conclusion