Bridgman growth and electrical properties of Nd-doped PMN–PT single crystal with ultrahigh piezoelectricity

Abstract

Using the polycrystalline material with a nominal composition of Nd_0.01Pb_0.985[(Mg_1/3Nb_2/3)_0.70Ti_0.30]O₃, an Nd-doped PMN–PT single crystal has been grown successfully by a vertical Bridgman process. The perovskite structure and the crystalline phase evolution of the as-grown crystal were confirmed by X-ray diffraction analysis. A series of (001)-oriented crystal wafers, fabricated from different regions of the as-grown crystal boule, were characterized systematically to verify their electrical properties. Compared to the undoped PMN–PT single crystal, the crystal wafers under direct current polarization exhibited an improved piezoelectric coefficient d₃₃ of 1780–2870 pC N⁻¹, along with a lower phase transition temperature T and a lower Curie temperature T_c in the range of 55–63 °C and 95–141 °C, respectively. The coercive field E_c and the remnant polarization P_r for the crystal wafers were measured to be 1.7–2.7 kV cm⁻¹ and 23.9–32.7 μC cm⁻², respectively. It was found that the piezoelectric coefficient d₃₃ of the crystal wafer could be even elevated to the range 2200–3650 pC N⁻¹ by applying alternating current polarization. The improved piezoelectricity for the crystal wafer under alternating current polarization may be associated with the increased domain density inside the crystal medium.