Thickness‐Dependent Properties of Relaxor‐PbTiO₃ Ferroelectrics for Ultrasonic Transducers

Abstract

The electrical properties of Pb(Mg1/3Nb2/3)O3-PbTiO3 (PMN-PT) based polycrystalline ceramics and single crystals were investigated as a function of scale ranging from 500 microns to 30 microns. Fine-grained PMN-PT ceramics exhibited comparable dielectric and piezoelectric properties to their coarse-grained counterpart in the low frequency range (<10 MHz), but offered greater mechanical strength and improved property stability with decreasing thickness, corresponding to higher operating frequencies (>40 MHz). For PMN-PT single crystals, however, the dielectric and electromechanical properties degraded with decreasing thickness, while ternary Pb(In1/2Nb1/2)O3-Pb(Mg1/3Nb2/3)O3-PbTiO3 (PIN-PMN-PT) exhibited minimal size dependent behavior. The origin of property degradation of PMN-PT crystals was further studied by investigating the dielectric permittivity at high temperatures, and domain observations using optical polarized light microscopy. The results demonstrated that the thickness dependent properties of relaxor-PT ferroelectrics are closely related to the domain size with respect to the associated macroscopic scale of the samples.

Mechanical Confinement: An Effective Way of Tuning Properties of Piezoelectric Crystals

“…[1][2][3][4][5][6][7][8][9][10] Due to their ultrahigh piezoelectric properties, these single crystals are of great interest for many different electromechanical device applications. [3,10] The piezoelectric properties of these crystals vary markedly with the chemical composition in the vicinity of the morphotropic phase boundary (MPB), which separates a rhombohedral perovskite structure at low PT-content from a tetragonal perovskite at high PT-content. [7][8][9] Detailed structural analysis on the PMN-PT system reveals that the MPB spans from 30 to 38 mol.% of PT within which a monoclinic (MC) phase coexists with the rhombohedral (30~32 mol.%) or the tetragonal (32~38 mol.%) phase.…”

[111]-oriented PIN-PMN-PT crystals with ultrahigh dielectric permittivity and high frequency constant for high-frequency transducer applications

“…For the [001]-poled rhombohedral crystals, as reported in previous literatures, 8 an obvious decrease of electromechanical properties appears when the operational frequency is higher than 10 MHz (i.e., the thickness of an [001]-poled rhombohedral PMN-PT crystal is less than 0.15 mm). Thus, scaling effects were also investigated for the [111]-poled tetragonal crystals.…”

“…The dielectric permittivity has been reported to be reduced with decreasing the thickness of both PZT ceramics and PMN-PT crystals due to the scaling effect. 8 To address the issues above from a material viewpoint, piezoelectric elements with significantly higher dielectric permittivities (electrically "soft") and higher frequency constants (elastically "stiff") are essential. For a piezoelectric element with fixed aspect ratio (r ¼ w/t, where w and t are width and thickness, respectively), its capacitance can be expressed by…”

Phase diagram and dielectric properties of Pb(In1/2Nb1/2)O3-Pb(Mg1/3Nb2/3)O3-PbTiO3 ceramics

“…[1][2][3][4][5][6][7] However, the low rhombohedral to tetragonal phase transformation temperature (T rÀt ) and Curie temperature (T c ) prevent the use of PMN-PT crystal in high temperature environment. PIN content was added in PMN-PT system to broader the temperature usage of relaxor-based crystals.…”