The largest Pb(In1/2Nb1/2)O-3-PbTiO3(PIN-PT) binary system single crystal (about 20 mm x 10 mm x 5 mm, 4.5 g) near the morphotropic phase boundary composition with well-developed (1 0 0) planes was grown by the flux method using PbO-PbF2-B2O3 flux. The PIN-PT(72/28) single crystal was found by simultaneous microdifferential thermal analysis and thermogravimetric analysis to show a peritectic melting at 1283 degreesC with a partial decomposition of the perovskite crystal into a pyrochlore phase, followed by a liquidus point at 1294 degreesC. The electromechanical coupling coefficient in rectangular bar mode, k(33)' =78%, for phased array ultrasonic transducers was obtained by using the rhombohedral PIN-PT(72/28) single crystal oriented along the [0 0 1] axis. k(33)' = 78% is the highest value reported so far among all the piezoelectric materials with a T-c > 250 degreesC and is almost independent of temperature, and even at 200 degreesC decreased only by about 5%. The piezoelectric constant d(33)=700pC/N was obtained. The relative permittivity E, decreases after poling. For instance, the epsilon (r) value of 2650 before poling, decreases to 1500 after poling.