Tunable dislocations overcome mechano-functional tradeoff in perovskite oxides

TL;DR

This study demonstrates how tunable dislocation densities in KTaO3 can induce a brittle-ductile-brittle transition, enabling simultaneous optimization of mechanical and functional properties in perovskite oxides.

Contribution

It uncovers a novel dislocation density-dependent transition in ceramics and introduces a framework for designing materials with balanced mechanical and functional performance.

Findings

Dislocation densities cause a brittle-ductile-brittle transition in KTaO3.

Intermediate dislocation densities enable over 20% ductility.

Higher dislocation densities decrease thermal conductivity, revealing a tradeoff.

Abstract

Recent advancements in dislocation engineering are reshaping the traditional view towards ceramics being brittle. Here, we use KTaO3 (KTO), a perovskite oxide that is newly discovered with room-temperature bulk plasticity, and demonstrate that the seeded dislocations can effectively tune both mechanical and functional properties. We uncover a novel brittle-ductile-brittle (BDB) transition: low dislocation densities lead to brittle failure, intermediate densities (~10*14 m-2) enable superior ductility with strains over 20%, and high dislocation densities (~10*15 m-2) induce again brittle fracture. This dislocation density-dependent non-monotonic mechanical response challenges the traditional behavior of ceramics and offers new design opportunities. Furthermore, dislocation densities can monotonically decrease thermal conductivity, revealing a tradeoff between mechanical strength and functionality. The findings reveal a critical threshold of dislocation density in optimizing the performance of functional oxides, and provide a new framework for using dislocations to design advanced materials where mechanical durability and enhanced functionality are intertwined.