The crystallization and optical properties of LiNbO3 single crystals

LiNbO3 single crystals were grown by the Czochralski technique in an air atmosphere. The critical crystal diameter D-c = 1.5 cm and the critical rate of rotation omega(c) = 35 rpm were calculated from the dynamic of fluids equations for buoyancy-driven and forced convections under which thr: shape of the melt/crystal interface changed. The domain inversion was carried out at 1473 K using a 10 min 3.75 V/cm electric field. The obtained crystals were cut, polished and etched to determine the presence of dislocations and single domain structures. The lattice parameters n = 0.51494 nm, c = 3 were determined by X-lay powder diffraction. The 1.38620 nm and V = 0.3186 nm(3) optical properties were studied by infrared spectroscopy in the wave number range 20-5000 cm(-1). With decreasing temperature, an atypical behaviour of the phonon modes, due to the ferroelectric properties of LiNbO3 single crystal, could be seen. The optical constants were calculated by Kramers-Kronig analysis and the value of the critical temperature was estimated. The obtained results are discussed and compared with published data.