Study of Dielectric Properties and Phase Transformation of Thermally Modified Nano-Composite PbIn1/2Nb1/2O3

Abstract

Differential thermal analysis as well as Raman and dielectric studies of PbIn1/2Nb1/2O3 single crystals exhibiting a different degree of order were performed. For this purpose two ordering procedures were applied. In Procedure A the as grown crystals were annealed at 650°C for different periods of time. Whereas in Procedure B the crystals were annealed at various temperatures, ranging from 650 to 850°C, long enough to reach the thermodynamic equilibrium state. With the increase of the degree of order, the heat anomaly related to the antiferroelectric-paraelectric phase transitions in the ordered regions, increase and shifts towards higher temperatures. Simultaneously the diffuse and frequency dependent maximum of the dielectric permittivitty ϵ(T), characteristic for disordered crystals, gradually forms a sharp maximum typical for ordered crystals and shifts towards higher temperatures. The evolution of Raman spectra at room temperature also indicates their sensitivity to the ordering state. Systematic dielectric investigations allowed us to distinguish two contributions to the dielectric response, one originating from the antiferroelectric and other from the ferroelectric nano-regions. The diagrams showing temperatures of the observed phase transitions versus annealing conditions as well as the coexistence of different phases are given in the paper. The experiments performed showed that lead indium niobate presents a thermally modified nano-composite structure composed of ordered antiferroelectric regions embedded in a disordered ferroelectric matrix.