Growth of potassium sodium niobate single crystals by solid state crystal growth

Single crystals of (K0.5Na0.5)NbO3 have been grown for the first time by the solid state crystal growth process. A KTaO3 seed crystal was embedded in a matrix of (KxNa1−x)NbO3 powder with a nominal composition of (K0.5Na0.5)NbO3. K4CuNb8O23 was used as a liquid-phase sintering aid. During sintering a single crystal of (K0.5Na0.5)NbO3 grew on the KTaO3 seed. Scanning electron microscopy energy dispersive X-ray spectroscopy (SEM-EDS) showed that Ta did not migrate into the single crystal and that the single crystal had a composition very close to that of the nominal value. SEM-EDS showed that the single crystal and the matrix grains had the same composition within the limits of experimental error. Transmission electron microscopy (TEM) confirmed that the grown material was indeed single crystalline and had grown epitaxially on the seed crystal. The single crystal contained a considerable amount of porosity, which could be reduced by pre-densification of the matrix by hot pressing.