The constitutional supercooling in single crystal grown by Czoehralski method has been studied by observing grind and polished and etched specimen with microscopy method. Structure transition temperature of the SNLN crystals has been studied under high temperature utilizing polarization lightmicroscope. The constitutional supercooling and internal growth striation in the SNLN crystals have been overcome and the optical homogeneity of the crystals have been improved by employing optimum growth condition and technique.