Shear Piezoelectric and Dielectric Properties of ${\hbox {LiNbO}}_{3}$, PMN-PT and PZT-5A at Low Temperatures

Abstract

We have measured the low-temperature shear piezoelectric and dielectric constants of single-crystal lithium niobate ($\hbox {LiNbO}_{3}$) and lead magnesium niobate–lead titanate (PMN-PT), and of ceramic lead zirconium titanate (PZT-5A) transducers between room temperature and 78 mK. The piezoelectric and dielectric coefficients $d_{15}$ and $K^{\sigma }_{15}$ all decrease with temperature, although the total change in $d_{15}$ is only about 7% for $\hbox {LiNbO}_3$. The values of $d_{15}$ for PZT-5A and PMN-PT are much larger at room temperature but decrease much more rapidly, by factors of 4 for PZT-5A and 10 for PMN-PT. For $\hbox {LiNbO}_3$, $d_{15}$ is constant below 50 K, but in both PZT-5A and PMN-PT $d_{15}$ continues to decrease nearly linearly to the lowest temperatures. The behavior of the dielectric constant of each material mirrors that of $d_{15}$, reflecting their common ferroelectric origins. The piezoelectric voltage constants $g_{15}$ are similar in the three materials and are only weakly temperature dependent. For actuator applications where large displacements are needed, PMN-PT and PZT-5A have much larger $d_{15}$ values than $\hbox {LiNbO}_3$, but this advantage essentially disappears at low temperatures and $\hbox {LiNbO}_3$ is a better choice in many applications. For sensor applications where $g_{15}$ determines a transducer’s output voltage, the three materials have similar sensitivity for high-frequency applications like ultrasonics. At low frequencies, however, they are less sensitive as voltage sensors and the use of charge or current amplifiers is preferable.