Rare-earth effect on the physical properties of Na$_{0.5}$Bi$_{0.5}$TiO$_3$ system: A Density Functional Theory investigation

TL;DR

This study uses density functional theory to explore how different rare-earth elements influence the structural, electronic, and magnetic properties of Na$_{0.5}$Bi$_{0.5}$TiO$_3$ compounds, revealing correlations between composition, polarization, and disorder.

Contribution

It provides a comprehensive first-principles analysis of rare-earth doping effects on Na$_{0.5}$Bi$_{0.5}$TiO$_3$, including polarization, electronic structure, and chemical ordering insights.

Findings

High polarization correlates with increased TiO$_6$ distortion.

Rare-earth elements induce magnetization via 4f orbitals.

Dysprosium doping increases A-site disorder and relaxor behavior.

Abstract

Na$_{0.5}$(Bi$_3$/4RE$_{1/4}$)$_{0.5}$TiO$_3$ (RENBT, RE = Nd, Gd, Dy, and Ho) compounds were investigated in the framework of first-principles calculations using the full potential linearized augmented plane wave (FP-LAPW) method based on the spin-polarized density functional theory implemented in the WIEN2k code. Combined charge density distribution and Ti K-edge x-ray absorption spectra revealed that the RENBT compositions with high polarization values were accompanied by a higher TiO$_6$ distortion, DyNBT, and NdNBT compounds. The effect of the rare-earth elements on the polarization were confirmed experimentally with the collection of the hysteresis loops. The investigation of the electronic properties of the compounds highlighted the emergence of a magnetization owing to the 4f orbital effect of the rare-earth elements. Besides, the investigation of the chemical ordering showed a short-range chemical ordering for the pure composition and an increased A-site disorder for dysprosium doped NBT system. The increased disorder may speak for increased relaxor properties in the RE doped compositions.