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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.

The Pb(Yb1/2Nb1/2)O3–PbTiO3 (PYN–PT) binary system single crystal near the morphotropic phase boundary (MPB) composition with (100) planes of 1–2 mm length on one side was successfully grown by the flux method using PbO–PbF2–B2O3 flux. The PYN–PT (47/53) single crystal was found, by simultaneous microdifferential thermal analysis and thermogravimetric analysis, to show a peritectic melting point at 1205°C with a decomposition of the perovskite crystals into a pyrochlore phase and a liquidus point at 1253°C. The structure of the PYN–PT (47/53) single crystal was determined by X-ray diffraction study to be tetragonal with a=4.05±0.01 A and c=4.14±0.01 A at room temperature. The PYN–PT single crystal shows the maximum value of the relative permittivity ε r of 16000 at 1 kHz at a Curie temperature T c of 404°C, which is as high as that in the Pb(Zr, Ti)O3 system near the MPB and the value of the remanent polarization P r of about 26 µC/cm2 at 140°C.