What is it about?
There is a growing demand for integration of miniaturized piezoelectric devices in different applications due to their high efficiency compared to electromagnetic devices. Since many of high-power piezoelectric devices are working under external mechanical stress loads, their overall performance is largely affected by these external biases. Therefore, we have studied the effect of external mechanical bias on a popular piezoelectric material. We have addressed different setbacks in the conventional methodologies used for study of mechanical stress effect on piezoelectric material properties, including spurious modes and clamping effect. Accordingly, we have developed a novel methodology which was able to overcome these setbacks using a unique transducer design. We have measured the stress dependency of piezoelectric loss parameters for the first time, and we have found that external mechanical loads can improve the device performance, especially in applications such as underwater transducer. The elastic loss showed a significant decrease compared to dielectric loss, which shows that the material heat generation at high power applications and resonance frequency applications can be considerably enhanced. Also, we have reported that piezoelectric loss increases under compressive stress, for the first time.
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Why is it important?
Our studies are very important for achieving a better understanding of the loss mechanism as a physical phenomenon, while additionally improving the performance of existing simulation software. In contrast with IEEE standard the quality factors at resonance (QA) and antiresonance (QB) are not equal. In the case of PZT it is well known that QB>QA. According to our study quality factor at both resonance and antiresonance increases under compressive stress. Accordingly, not only using antiresonance frequency is recommended application of pre-stress can also improve the performance of PZT at antiresonance frequency. Overall, our findings allow for better approaches for design, production, and development of piezoelectric devices, in a wide range of piezoelectric applications.
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This page is a summary of: Compressive stress effect on the loss mechanism in a soft piezoelectric Pb(Zr,Ti)O3, Review of Scientific Instruments, July 2019, American Institute of Physics, DOI: 10.1063/1.5096905.
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DC bias electric field and stress dependence of piezoelectric parameters in lead zirconate titanate ceramics – Phenomenological approach
The piezoelectric material behavior, including loss mechanism, under external DC electric field and stress biases have been extensively studied in lead zirconate titanate ceramics. However, in order to achieve a better understanding of these effects, development of a comprehensive model is required. The purpose of this paper is to develop a phenomenological model to explain the nonlinear nature of piezoelectric parameters under DC bias electric field and stress. Therefore, the Landau-Devonshire energy function considering external biases was developed and accordingly the material properties were derived, based on first order approximation. In order to explain the compliance and piezoelectric constants change higher order elastic and electrostrictive terms were introduced into the Gibb's free energy function. Accordingly, thermodynamic theory parameters, including higher order parameters, of a soft PZT were measured and characterized based on inverse permittivity behavior near Curie temperature. Finally, the phenomenological model predictions of material property changes under DC bias electric field and compressive stress were compared with experimental data reported by our group. The proposed model succeeded to explain the material properties change under external biases. Furthermore, the effect of DC electric field and compressive stress on loss parameters were explained based on domain wall motion.
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