High-temperature solution growth and characterization of the piezo-/ferroelectric (1-x)Pb(Mg_1/3Nb_2/3)O₃-xPbTiO₃ [PMNT] single crystals

Relaxor ferroelectric-based single crystals (1-x)Pb(Mg_1/3Nb_2/3)O₃-xPbTiO₃ [PMNT] (x = 0.1-0.5) were grown from high-temperature solutions, using PbO or PbO/B₂O₃ as flux. The effects of chemical and thermodynamic parameters on the growth results were systematically studied. The optimum flux composition and concentration was found to be (49 wt% PbO+1 wt% B₂ O₃), which led to the stabilization of the perovskite crystals against the pyrochlore phase, and to the growth of high-quality PMNT crystals suitable for subsequent characterization. The B₂O₃ additive was shown to play an important role in improving the effectiveness of the PbO solvent by providing an optimum degree of complex formation and an adequate viscosity. Top seeding technique can substantially modify the nucleation kinetics. The crystal morphology was related to a layer growth mechanism controlled by two-dimensional nucleation and to the growth sectors. The local composition of the grown crystals was analyzed by laser ablation ICP mass spectrometry. It shows a fluctuation up to about ±5% of the Ti⁴⁺ concentration from its nominal composition for 0.65 PMN-0.35 PT crystals. The dielectric properties and phase transitions of the grown PMNT crystals were characterized and discussed in relation with the Ti-concentration on the B-site.