Thickness-dependent properties of relaxor-PbTiO3 ferroelectrics for ultrasonic transducers

The electrical properties of Pb(Mg1/3Nb2/3)O 3-PbTiO3 (PMN-PT)-based polycrystalline ceramics and single crystals were investigated as a function of scale ranging from 500 μm to 30 μm. Fine-grained PMN-PT ceramics exhibited comparable dielectric and piezoelectric properties to their coarsegrained counterpart in the low frequency range (\u3c10 \u3eMHz), but offered greater mechanical strength and improved property stability with decreasing thickness, corresponding to higher operating frequencies (\u3e40 MHz). For PMN-PT single crystals, however, the dielectric and electromechanical properties degraded with decreasing thickness, while ternary Pb(In1/2Nb1/2)O3- Pb(Mg 1/3Nb2/3)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 ferro- electrics are closely related to the domain size with respect to the associated macroscopic scale of the samples. 2010 WILEY-VCH Verlag GmbH & Co. KGaA