Thermophysical Properties of a New Nonlinear Optical Na3La9O3(BO3)8 Crystal

Abstract

New nonlinear crystal Na3La9O3(BO3)8 (NLBO) with good optical quality and weighing 45 g with size of 38 × 30 × 20 mm3 has been grown by the optimized top-seeded solution growth (TSSG) method. Thermophysical properties including melting point, specific heat, thermal expansion, thermal diffusion, and hardness were performed on the crystal to determine thermal behaviors along different crystallographic axes. The specific heat was measured to be 0.45−0.70 J·g−1·K−1 in the temperature range from 20 to 300 °C, which is lower than that of β-BaB2O4(BBO), LiB3O5 (LBO), and CsLiB6O10 (CLBO). The Vickers hardness were measured to be 1052.67 kg/mm2 for (100) and 1239.67 kg/mm2 for (001) faces, which are greater than most of the commonly used borate crystals such as BBO, LBO, CsB3O5 (CBO), BiB3O6 (BIBO), KBe2(BO3)F2 (KBBF), K2Al2B2O7 (KABO), etc. The thermal expansion coefficients were measured to be αx = αy = 7.8 × 10−6 K−1, and αz = 15.3 × 10−6 K−1, resulting in weaker expansion anisotropy than those of BBO, LBO, BIBO, CBO, CLBO, KBBF, La2CaB10O19 (LCB), etc.