Scaling effects of relaxor-PbTiO3 crystals and composites for high frequency ultrasound

The dielectric and piezoelectric properties of Pb(Mg1/3Nb2/3)O3–PbTiO3 (PMN-PT) and Pb(In1/2Nb1/2)O3–Pb(Mg1/3Nb2/3)O3–PbTiO3 (PIN-PMN-PT) ferroelectric single crystals were investigated as a function of thickness/scale in monolithic and piezoelectric/polymer 1–3 composites. For the case of PMN-PT single crystals, the dielectric (ε33T/ε0) and electromechanical properties (k33) were found to significantly decrease with decreasing thickness (500–40 μm), while minimal thickness dependency was observed for PIN-PMN-PT single crystals. Temperature dependent dielectric behavior of the crystals suggested that the observed thickness dependence in PMN-PT was strongly related to their relatively large domain size (>10–20 μm). As anticipated, 1–3 composite comprised of PIN-PMN-PT crystals exhibited superior properties to that of PMN-PT composite at high frequencies (>20 MHz). However, the observed couplings, being on the order of 80%, were disappointedly low when compared to their monolithic counterparts, the result of surface damage introduced during the dicing process, as evidenced by the broadened [002] peaks in the x-ray diffraction pattern.