Growth and electrical properties of (Mn,F) co-doped 0.92Pb(Zn _1/3Nb_2/3)O₃-0.08PbTiO₃ single crystal

The growth and characterization of (Mn,F) doped Pb(Zn_1/3Nb _2/3)O₃-PbTiO₃ (PZNT) single crystals are reported in this paper. The typical single crystal obtained is up to 30mm size with dark brown color. The crystal lattice parameters of doped PZNT crystal are slightly decreased compared to the pure one. The room temperature dielectric permittivity along 〈001〉 direction is about 6000, which is lower than that of the pure PZNT8 because of the dopants. The Curie temperature of the doped crystal is about 180°C while the ferroelectric phase transition temperature is around 100°C, which are higher than those of the pure PZNT8 single crystal. The remnant polarization and coercive field of 〈001〉 oriented doped crystal measured at 1Hz and 10kV/cm field are about 27μC/cm² and 4.2kV/cm, respectively. The room temperature mechanical quality factor is ∼300. Piezoelectric coefficient of 〈001〉 oriented doped crystal is higher than 3500pC/N and the longitudinal electromechanical coupling factor is larger than 93%. The piezoelectric properties of doped PZNT single crystal with temperature and orientations are also reported in this paper. The valence state of the manganese dopant was determined by electron spin resonance, indicating no Mn⁴⁺ in the crystals, suggesting the valence of manganese ions in PZNT crystals may be 2+, which acts as a hardener, stabilizes the domain wall and pins the domain wall motion, on the other hand, the dopant will enter Ti⁴⁺ position, shifting the crystal composition to higher PT content.