Grain growth control and solid-state crystal growth by Li2O/PbO addition and dislocation introduction in the PMN-35PT system

Grain growth behavior and solid-state single crystal growth (SSCG) in the Pb(Mg1/3Nb2/3)O-3-35 mol% PbTiO3 (PMN-35PT) system have been investigated with varying Li2O/PbO ratios. The effect of dislocation density on crystal growth has also been studied. For SSCG, a BaTiO3 single-crystal seed was embedded in a polycrystalline PMN-PT matrix. During annealing, a PMN-PT single crystal grew from the seed at the cost of the small matrix grains. Addition of Li2O dopant first enhanced and then reduced abnormal grain growth in the matrix. In the 2 mol% Li2O and 6 mol% PbO excess PMN-PT samples annealed at 1200 degrees C, considerable single-crystal growth occurred without formation of abnormally large grains in the matrix. Increasing the dislocation density in the BaTiO3 seed crystal resulted in enhanced growth of single crystals. These results were explained in terms of interface reaction-controlled nucleation and growth, based on crystal growth theories.