Characterization of pure and substituted 0.955Pb(Zn1/3Nb2/3)O3-0.045PbTiO3

Ferroelectric single crystals Pb(Zn1/3Nb2/3)O3-PbTiO3 (PZN-PT) are promising full materials for non-resonant or large bandwidth transducers due to the large values of their piezoelectric properties (dij, kij) and their low mechanical quality factor (Qij). The growth and characterization of pure and Mn-doped PZN-PT single crystals are reported in this paper. Crystals of pure and 1 mol% Mn-doped PZN-4.5PT were grown by a Flux technique. The typical single crystals obtained are brown yellow for the pure PZN-4.5PT and black for the Mn-doped PZN-4.5PT. The crystal lattice parameters of doped PZN-PT crystals are slightly increased compared with the pure one. The room temperature dielectric permittivity along the 〈0 0 1〉 direction is about 3500, which is lower than that of the pure PZN-4.5PT. The Curie temperature Tc of the doped crystal is about 178 °C (which is higher than that of the pure crystal (166 °C)), while the ferroelectric phase transition temperature is 124 °C (lower than that of the pure crystal (130 °C)). The remnant polarization and coercive field of 〈0 0 1〉 oriented doped crystal measured at 1 kHz are around 31 μC/cm2 and 4.46 kV/cm, respectively, 27 μC/cm2 and 3.32 kV/cm for the pure crystal. Piezoelectric charge coefficients of the 〈0 0 1〉 oriented doped crystal are about 1560 pC/N and −542 pC/N, respectively, for the longitudinal and the transverse modes. The mechanical quality factor Qm is around 400 for the doped single crystals at room temperature, larger than that of the pure single crystals. The valence state of the manganese dopant was determined by electron spin resonance indicating that the manganese is in majority in its lowest valence 2+. Physicochemical properties (such melting point, dilatation parameter and contents) were also determined. The variation of the piezoelectric coefficient d31 versus temperature and the d33 versus uniaxial stress shows that these coefficients are more stable for the doped crystals than for the pure one.