Evolution of Microstructure and Relaxor Ferroelectric Properties in (La_zBa_(1-z)(Ti0.80Sn0.20)O3

TL;DR

This study explores how lanthanum doping influences the microstructure and relaxor ferroelectric properties of barium stannate-titanate ceramics, revealing microstructure evolution and relaxor behavior at specific doping levels.

Contribution

It provides new insights into the microstructure-property relationship in La-doped BTS ceramics, highlighting the effects of La on grain growth and relaxor behavior.

Findings

La doping inhibits grain growth at low levels

Higher La doping leads to leafy grain microstructures

Relaxor behavior observed at 2-3% La doping

Abstract

We report a study on a series of lanthanum doped barium stannate-titanate (LBTS) ceramics towards correlating their microstructure with ferroelectric properties. The samples were prepared by solid state reaction technique and the XRD analysis indicated predominantly single phase microstructure. Scanning Electron Microscopy revealed that while a low La doping of 1 atomic % yielded inhibited grain growth in 1LBTS, higher amounts of La doping yield larger leafy grains. This peculiar grain growth and microstructure evolution could be attributed to the combination of the following two competing factors: (i) suppression of O vacancies due to La doping leading to grain growth inhibition and (ii) enhancement of mechanism leading to nucleation and growth of 2-D (leafy) grains for La doping higher than 2 atomic % due to eutectic phenomena. Dielectric permittivity measurements indicate that addition of La enhances diffused phase transition in BTS, but its frequency dependence is observed only at 2 atomic % La doping. This signature relaxor behaviour and the increase in the intensity of a particular Raman peak with La doping, as well as non-saturated PE hysteresis loops confirm the presence of polar nano-regions for 2 and 3 atomic % La doped BTS. However significant enhancement in dielectric permittivity could not be achieved due to reduced grain size.