Piezoelectric Properties of a High Curie Temperature Pb(In1/2Nb1/2)O3–PbTiO3 Binary System Single Crystal near a Morphotropic Phase Boundary

High-quality piezoelectric (1-x)Pb(In1/2Nb1/2)O3–xPbTiO3 binary system single crystals near a morphotropic phase boundary were successfully grown by a conventional flux method using PbO–PbF2–B2O3 flux. The largest crystal had dimensions of about 20 mm×10 mm×5 mm. The permittivity shows a shoulder at the ferroelectric rhombohedral to tetragonal phase transition temperature, T fr=100°C, and then has a maximum (35000 at 1 kHz) at the ferroelectric tetragonal to paraelectric cubic phase transition temperature, T c=260°C. The electromechanical coupling coefficient in rectangular bar mode, k 33 ′=78%, for phased array ultrasonic transducers was obtained by using the rhombohedral 0.72Pb(In1/2Nb1/2)O3–0.28PbTiO3 single crystal oriented along the [001] axis in the shape of a rectangular bar of 0.2 mm in width, 0.5 mm in thickness and 9 mm in length. The k 33 ′=78% is the highest value reported so far among all the piezoelectric materials with a T c more than 250°C.