# Bulk Acoustic Wave Resonance Characteristics of PMN-PT Orthorhombic Crystal Plates Excited by Lateral Electric Fields

## TL;DR

This paper studies how lateral electric fields affect acoustic wave resonance in PMN-PT crystal plates, offering insights for optimizing sensor designs.

## Contribution

A new model using Mindlin theory and FEM simulations to analyze and optimize LFE BAW devices based on orthorhombic crystals.

## Key findings

- Motional capacitance, resonant frequency, and mode shape were determined for LFE BAW devices.
- Electrode parameters significantly influence resonance characteristics of the devices.
- Structural parameters affect mass sensitivity, verified through FEM simulations.

## Abstract

For relaxor ferroelectric single crystal (1 − x)Pb(Mg1/3Nb2/3)O3 − xPbTiO3 (PMN-PT), through reasonable component regulation and electric field polarization, an orthogonal mm2 point group structure can be obtained, which has high piezoelectric constants and is, therefore, a desired substrate material for lateral-field-excited (LFE) bulk acoustic wave (BAW) devices. In this work, acoustic wave resonance characteristics of (zxt) 45° PMN-PT BAW devices with LFE are investigated. Firstly, Mindlin first-order plate theory is used to obtain vibration governing equations of orthorhombic crystals excited by a lateral electric field. By analyzing the electrically forced vibrations of the finite plate, the basic vibration characteristics, such as motional capacitance, resonant frequency, and mode shape are obtained, and influences of different electrode parameters on resonance characteristics of the device are investigated. In addition, the effects of the structure parameters on the mass sensitivity of the devices are analyzed and further verified by FEM simulations. The model presented in this study can be conveniently used to optimize the structural parameters of LFE bulk acoustic wave devices based on orthorhombic crystals, which is crucial to obtain good resonance characteristics. The results provide an important basis for the design of LFE bulk acoustic wave resonators and sensors by using PMN-PT orthorhombic crystals.