Characterization of piezocrystals for practical configurations with temperature- and pressure-dependent electrical impedance spectroscopy

Abstract

Piezoelectric single crystal materials such as (x)Pb(Mg(1/3)Nb(2/3))O(3-)(1-x)PbTiO(3) (PMN-PT) have, by some measures, significantly better performance than established piezoelectric ceramics for ultrasound applications. However, they are also subject to phase transitions affecting their behavior at temperatures and pressures encountered in underwater sonar and actuator applications and in non-destructive testing at elevated temperatures. Materials with modified compositions to reduce these problems are now under development, but application-oriented characterization techniques need further attention. Characterization with temperature variation has been reported extensively, but the range of parameters measured is often limited and the effects of pressure variation have received almost no attention. Furthermore, variation in properties between samples is now rarely reported. The focus of this paper is an experimental system set up with commercially available equipment and software to carry out characterization of piezoelectric single crystals with variation in temperature, pressure, and electrical bias fields found in typical practical use. We illustrate its use with data from bulk thickness-mode PMN-29%PT samples, demonstrating variation among nominally identical samples and showing not only the commonly reported changes in permittivity with temperature for bulk material but also significant and complicated changes with pressure and bias field and additional ultrasonic modes which are attributed to material phase changes. The insight this provides may allow the transducer engineer to accelerate new material adoption in devices.

Functional Piezocrystal Characterisation under Varying Conditions

“…Given the variation in material properties along a crystal boule and potential variations in poling, the use of multiple samples to provide subsets of the elastoelectric matrix raises the possibility of inconsistency in the matrix and this has been found to be the case in practice [15]. Therefore, the alternative methods outlined previously are under development, with the aim to reduce the number of samples required [13,14].…”

“…Most measurements were carried out on Generation II and III, 33% PIN-PMN-PT and Mn:PIN-PMN-PT samples, respectively, while we also include measurement results on PMN-29% PT samples from the literature [15] where they provide useful data for this paper. Effects of increased environmental temperature and pressure were investigated under passive conditions, i.e.…”

“…Whilst the full elastoelectric matrix is necessary for detailed transducer design using contemporary computer-modelling and virtual prototyping tools such as finite element analysis (FEA, e.g., PZFlex, Weidlinger Associates Inc., Mountain View, CA, USA), it is also possible to gain significant insight into piezocrystal properties and behaviour through characterisation of specific sample configurations [15]. This approach is appropriate when new materials are in development, both piezocrystals and other types such as Pb-free piezoceramics [16].…”

Acoustic Devices for Particle and Cell Manipulation and Sensing

“…Relaxor-based ferroelectric piezocrystals, e.g., PMN-PT, PIN-PMN-PT, and Mn:PIN-PMN-PT, exhibit much higher piezoelectric constants and electromechanical coupling coefficients than conventional PZT [71,72], e.g., d 33 > 1300 pC/N and k 33 ≈ 0.9. These piezocrystals are usually implemented in the form of piezocomposites [72] because this form of material exploits the high values of d 33 and k 33 , allowing for the fact that k t ≈ 0.5 is similar to that of conventional piezoceramics.…”

“…In the models, PMN-PT was assigned properties reported in the literature [71] and other materials were assigned properties defined in the PZFlex libraries. The dimensions of each PMN-PT pillar were 100 × 100 × 450 μm 3 .…”