Study of Structural Electrical and Optical Properties of Some Rare Earth Co Doped Strontium Titanate Ceramics

Abstract

The lead-free perovskite materials have attracted much attention for their newlinecharacteristics properties like super-conductivity, insulator-metal transition, newlineferroelectricity, insulator property, and ionic conductivity. These properties can be newlineexploited for modern device applications. For this present work, polycrystalline newlineLa0.1Sr0.9-xNdxTiO3 (series-1) and La0.1Sr0.9-xGdxTiO3 (series-2) with x=0.05, 0.07, newline0.09, and 0.11 samples are synthesized using solid state reaction technique and newlineinvestigated for their structural, microstructure, dielectric, electrical, and optical newlineproperties. X-ray diffraction (XRD) analysis using Fullprof software confirms the newlineformation of desired structures. The SEM results show a coherent change in grain size newlinefor both the series of samples by observing the arrangement of grains, grain newlineboundaries, and pores in the synthesized materials. The electrical characterization of newlinethe samples has been carried out over a wide temperature range (RT-4000C) and newlinefrequency (1kHz 1MHz) using a HIOKI 3570 LCR meter (Impedance analyzer). the newlinedielectric studies for series-1 samples, reflect an unprecedented increase in the newlinedielectric constant and subsequent decrease in tangent loss, with an increase in Nd newlinedoping. The superior dielectric behavior is attributed to the containment of the mobile newlinecharge carrier inside the grain due to the substantial increase in grain boundary barrier newlineproperties. However, in series-2 samples an unprecedented increase in the dielectric newlineconstant and subsequent decrease in tangent loss, with an increase in Gd doping is newlineobserved. The superior dielectric behavior is attributed to the containment of the newlinemobile charge carrier inside the grain due to the substantial increase in grain boundary newlinebarrier properties. The frequency dependent ac conductivity obeys Jonscher s newlineuniversal power law. The study of complex impedance spectroscopy for the samples newlinereveals that the conductivity has contribution from grains and grain boundaries, and newlinehas effects on the electrical properties. The evolution of grain boundary property is newlinefound to be due to the formation of double Schottky barrier ( newline newline newline). The PL newlineresults strongly support the presence of newline newlineand newline defects and formation of the newlinedouble Schottky barrier. But the same is due to the evolution of the secondary phase newlinein case of series-2 samples. The bandgap of all the samples in both series reduced newlinewith an increase in the Nd and Gd concentration. The La/Nd and La/Gd co-doped newlineSTO with a higher dielectric constant, lower dielectric loss, reduced bandgap, and inherent oxygen vacancies can be a novel paradigm for energy storage devices, newlinememory devices, and photocatalytic applications. newline newline