Tuning the piezoelectric and mechanical properties of the AlN system via alloying with YN and BN

TL;DR

This study uses density functional theory to demonstrate how co-alloying AlN with YN and BN can simultaneously enhance piezoelectric response and mechanical stiffness, enabling better design of multifunctional piezoelectric materials.

Contribution

It introduces a co-alloying strategy with YN and BN to tune both piezoelectric and mechanical properties of AlN, balancing electromechanical performance with stiffness.

Findings

YN increases piezoelectric response but softens the lattice.

Co-alloying with BN improves elastic properties.

The combined approach retains piezoelectric enhancements while enhancing stiffness.

Abstract

Recent advances in microelectromechanical systems often require multifunctional materials, which are designed so as to optimize more than one property. Using density functional theory calculations for alloyed nitride systems, we illustrate how co-alloying a piezoelectric material (AlN) with different nitrides helps tune both its piezoelectric and mechanical properties simultaneously. Wurtzite AlN-YN alloys display increased piezoelectric response with YN concentration, accompanied by mechanical softening along the crystallographic c direction. Both effects increase the electromechanical coupling coefficients relevant for transducers and actuators. Resonator applications, however, require superior stiffness, thus leading to the need to decouple the increased piezoelectric response from a softened lattice. We show that co-alloying of AlN with YN and BN results in improved elastic properties while retaining most of the piezoelectric enhancements from YN alloying. This finding may lead to new avenues for tuning the design properties of piezoelectrics through composition-property maps. Keywords: piezoelectricity, electromechanical coupling, density functional theory, co-alloying