Growth of Single Crystals of High-Curie-Temperature Pb(In1/2Nb1/2)O3–Pb(Mg1/3Nb2/3)O3–PbTiO3 Ternary Systems near Morphotropic Phase Boundary

Abstract

Crystal growth in xPb(In1/2Nb1/2)O3–yPb(Mg1/3Nb2/3)O3–zPbTiO3 (PIMNT100x/100y/100z) ternary systems near the morphotropic phase boundary was investigated by the conventional flux method using PbO and PbO–B2O3 flux. The PIMNT crystals were obtained easily by the slow cooling of a 50PIMNT:40PbO:10B2O3 (mol%) molten solution from 1230°C to 850°C. The PbO–B2O3 flux is effective for PIMNT single crystal growth. The largest PIMNT 16/51/33 crystal had dimensions of about 20 mm × 10 mm × 5 mm. The (001) wafers cut from the obtained crystal had transparent and opaque areas. The electron probe X-ray microanalysis (EPMA) results revealed that the compositions of the two areas differ slightly; the Ti content in the opaque area is lower than that in the transparent area. The temperature dependence of the dielectric constant showed a maximum at the tetragonal to cubic phase-transition temperature (Tc=187°C), which is 30°C–40°C higher than that for a 0.68Pb(Mg1/3Nb2/3)O3–0.32PbTiO3 (PMNT 68/32) single crystal. A dielectric constant (ε33T/ε0) of 4000, a coercive field (Ec) of 7.0 kV/cm, an electromechanical coupling factor (k33') of 80%, and a frequency constant (N33'r) of 1160 Hzm were obtained.