Loss characterisation of piezocrystals under elevated environmental conditions

摘要

Relaxor-based piezoelectric single crystals have experienced three generations of development, from binary (e.g. PMN-PT) through ternary (e.g. PIN-PMN-PT) to doped ternary (e.g. Mn:PIN-PMN-PT). With improved composition and other relevant factors, these materials exhibit an extraordinary degree of piezoelectricity and ultrahigh electromechanical coupling coefficients, making them suitable for applications requiring high sensitivity and high bandwidth. With further increases in rhombohedral-to-tetragonal phase transition temperature (TRT), coercive field (EC) and mechanical quality factor (Qm), these piezocrystals can now be expected to work at elevated temperature, T, and pressure, P, and with high electric field drive. However, in operation, material properties can vary and performance can degrade significantly because of these elevated conditions, and the situation can be exacerbated by losses in the materials, necessitating proper characterisation of loss factors. In this paper, we report an investigation of three different loss characterisation methods then propose one combined method, demonstrating its use on TE-mode plates of PIN-PMN-PT and Mn:PIN-PMN-PT. Characterisation was performed using impedance spectroscopy for 20°C ≤ T ≤ 100°C and 0 MPa ≤ P ≤ 60 MPa. Results relating to dielectric, elastic and piezoelectric losses are reported, with detailed analysis and comparisons.