Growth and characterization of single-crystal lead magnesium niobate–lead titanate via high-pressure vertical Bridgman method

Abstract

We have grown lead magnesium niobate–lead titanate (PMN–PT) single crystals, using the high-pressure vertical Bridgman (HPVB) technique, around the stoichiometric composition of 0.7 PMN–0.3PT [0.7Pb(Mg1/3Nb2/3)O3 + 0.3(PbTiO3)]. The final ingot (about 50-mm diameter, 25-mm long) was machinable using an inner diameter saw. The room-temperature x-ray diffraction on the starting powders and the final single crystal revealed a desirable perovskite structure. The natural growth direction in most of the crystals, as determined using orientation image microscopy, was (110). Examination of the final microstructures and phases/inclusions had been done using optical and infrared microscopy, energy dispersive spectroscopy, and x-ray backscatter techniques. Microstructural characterizations of the final ingots have revealed the presence of pores filled with Mg–Si–O-rich impurity phase, usually found along the cell boundary–like structures, in all the growths. We have measured some piezoelectric properties including d33 (1200 pC/N), k33 (0.85), kt (0.5), and the dielectric constant at the Curie temperature.