# Mechanisms of Concentric Ring Electrodes in Tuning the Performance of Z-Cut Lithium Niobate Ultrasonic Transducers

## TL;DR

This paper explores how concentric ring electrode designs affect the performance of lithium niobate ultrasonic transducers, showing that electrode geometry can significantly improve their efficiency and signal strength.

## Contribution

The study introduces a parametrized finite element model to systematically analyze how electrode geometry influences ultrasonic transducer performance.

## Key findings

- Optimizing electrode ring width increased the effective electromechanical coupling coefficient to 35.2%.
- Increasing electrode gap spacing further improved the coupling coefficient to 50.8%.
- Optimized electrode configurations boosted echo signal amplitude by up to 4.94 times compared to suboptimal designs.

## Abstract

Z-cut lithium niobate single crystal demonstrates considerable promise for contact-based ultrasonic nondestructive testing and structural health monitoring (SHM) transducers due to its high piezoelectric coefficients, strong electromechanical coupling capability, and environmentally friendly lead-free composition. As a simulation-based theoretical exploration, this study systematically investigates the impact of gap spacing and electrode width in concentric ring configurations on the resonant characteristics and pulse-echo response of ultrasonic transducers by establishing a parametrized finite element model. Numerical simulations reveal that electrode geometry plays a critical role in determining both the effective electromechanical coupling coefficient and echo signal strength. Optimizing the electrode ring width achieved an effective electromechanical coupling coefficient (keff) of 35.2%, while systematic enlargement of the electrode gap further enhanced this value to 50.8%. The study also demonstrates that optimized ring width and adjusted electrode spacing increased the echo signal’s peak-to-peak amplitude (Vpp) by factors of 4.94 and 2.03, respectively, compared to the poorest-performing configuration within each parameter group. This study establishes that precise design of concentric electrode configurations serves as an effective strategy for tuning lithium niobate ultrasonic transducer characteristics, providing critical design guidelines for developing high-performance ultrasonic transducers for solid medium coupling.