Stabilization mechanism of tetragonal structure in hydrothermal synthesized BaTiO$_3$ nanocrystal

TL;DR

This study investigates the stabilization of tetragonal BaTiO$_3$ nanocrystals synthesized hydrothermally with high OH concentration, revealing that OH anion configurations favor tetragonal distortion through combined experimental and ab initio analysis.

Contribution

It provides a microscopic understanding of how OH anions stabilize the tetragonal structure in BaTiO$_3$ nanocrystals, combining experimental FTIR/XRD data with ab initio calculations.

Findings

High OH concentration does not destabilize tetragonal BaTiO$_3$ nanocrystals.

Trans-type OH configurations favor tetragonal distortion.

Experimental data supports the ab initio geometric models.

Abstract

Higher OH concentration is identified in tetragonal barium titanate (BaTiO$_3$) nanorods synthesized by a hydrothermal method with 10 vol% ethylene glycol solvent [Inada, M. $et$ $al$. $Ceram.$ $Int.$ $2015$, $41$, 5581-5587]. This is apparently inconsistent with the known fact that higher OH concentration in the conventional hydrothermal synthesis makes pseudo-cubic BaTiO$_3$ nanocrystals more stable than the tetragonal one. To understand where and how the introduced OH anions are located and behave in the nanocrystals, we applied $ab$ $initio$ analysis to several possible microscopic geometries of OH locations, confirming the relative stability of the tetragonal distortion over the pseudo-cubic one due to the preference of trans-type configurations of OH anions. We also performed FTIR and XRD analysis, all being in consistent with the microscopic picture established by the $ab$ $initio$ geometrical optimizations.