Conoscopic study of strontium-barium niobate single crystals

Aleksandr Kolesnikov,Olga Malyshkina,Tadeusz Łukasiewicz,Aleksandra Ivanova,Yury Malyshkin,Jan Dec,Rostislav Grechishkin

doi:10.1088/1757-899x/49/1/012010

Abstract

Optically transparent single crystals of strontium-barium niobate, SrxBa1-xNb2O6, of different compositions (x = 0.26...0.7) were examined with the aid of conoscopic light interference figures. A regular change of the isochrome concentric ring number and diameters consistent with the temperature variation of the value of birefringence is demonstrated by direct observations of polar cuts of optically uniaxial samples. Anomalous violations of the conventional (uniaxial) interference patterns occur occasionaly in some samples being indicative of the existence of biaxial trait in their behaviour even though no voltage is applied. These features may depend on annealing treatments at elevated temperatures. The results of the study show that conoscopic images may serve as a sensitive indicator of the structural state of SBN crystals related to the effects of stress–induced change of optical anisotropy and temperature dependent birefringence parameters.

Highlights

Strontium barium niobate SrxBa1-xNb2O6 (SBN:x) lead-free environmentally friendly system represents a specific group of materials in which ferroelectric–relaxor behaviour depends on the x ratio Sr/(Ba+Sr) [1,2,3,4,5,6,7]
In the present work we applied the method of conoscopic light interference pattern to the study optical properties of SBN single crystals with different concentrations of strontium
It is seen that at room temperature (RT) the interference pattern is presented by isochromes in the form of regular concentric rings having superimposed isogyres in the shape of a maltese cross

Summary

IOP Publishing

A regular change of the isochrome concentric ring number and diameters consistent with the temperature variation of the value of birefringence is demonstrated by direct observations of polar cuts of optically uniaxial samples. Anomalous violations of the conventional (uniaxial) interference patterns occur occasionaly in some samples being indicative of the existence of biaxial trait in their behaviour even though no voltage is applied. These features may depend on annealing treatments at elevated temperatures. The results of the study show that conoscopic images may serve as a sensitive indicator of the structural state of SBN crystals related to the effects of stress–induced change of optical anisotropy and temperature dependent birefringence parameters

Introduction

Results and Discussion

Conclusion