Growth, optical and thermal properties of near-stoichiometric LiNbO3 single crystal

A near-stoichiometric LiNbO3 (N-SLN) single crystal of 40 mm in diameter and 60 mm in length has been grown by Czochralski method from a 58.5% Li melt in a platinum crucible. The fundamental absorption edge and IR absorption spectra were used for determining Li/Nb of the crystal. The measured specific heat of the crystal to be 0.6995 J g-1 K-1 is larger than that of congruent LiNbO3 (CLN) crystal to be 0.6010 J g-1 K-1 at 303.15 K. The thermal expansion coefficients along the two crystallographic directions in the measuring temperature range of 303.15-767.15 K have been measured to be aa = ab = 17.1807 K X 10-6 K and ac = 2.8769 K X 10-6 K, respectively. Thermal conductivity of near-stoichiometric LiNbO3 crystal is 5.234 W/m K and 4.434 W/m K at room temperature. The reason for larger anisotropic thermal expansion coefficients and larger thermal conductivity of N-SLN crystal than those of CLN crystal were discussed according to the structure of LiNbO3 crystal.