Growth of (Na0.5K0.5)NbO3 single crystals by abnormal grain growth method from special shaped nano-powders

Using the composite powders of (Na0.5K0.5)NbO3 (NKN) nano-particles and nano-rods as starting materials, the NKN single crystals were prepared by abnormal grain growth (AGG) method. The morphology evolution and the formation mechanism in the crystal growth process were investigated in detail. The results revealed that the average size and the apparent quantity of abnormal grains increased gradually with the increase of sintering temperature. The biggest NKN single crystals with size of about 3 mm were obtained at 950 °C for 2 h. Though the nano-particles and nano-rods have the same composition, the driving forces are distinctively different due to the diversity of grain morphology. The nano-rods have the large driving forces especially at high sintering temperature, which plays a dominant role in facilitating the formation of NKN single crystals during AGG process.