Physical Properties of a Promising Nonlinear Optical Crystal K3Ba3Li2Al4B6O20F

Beryllium-free nonlinear optical (NLO) crystal K3Ba3Li2Al4B6O20F (KBLABF) is a newly reported promising candidate in the generation of the significant UV coherent light. A 17 × 12 × 8 mm3 bulk single crystal is successfully grown with an optimized flux molar ratio. The crystal specific heat increases from 0.65 J·g–1·°C–1 to 0.96 J·g–1·°C–1 with the increasing temperature. Meanwhile, the a-direction thermal conductivity of KBLABF is 1.11 W·m–1·K–1 at 25 °C, which is also equivalent to that of the famous NLO crystal β-BaB2O4 (1.25 W·m–1·K–1). The KBLABF crystal has moderate Vickers hardness along the a-axis and c-axis (165.1 HV0.1 and 257.7 HV0.1, respectively), which indicates it is easy to be cut and polished. Remarkably, the laser damage threshold of KBLABF is 3.32 GW·cm–2 (1064 nm, 8 ns), which even exceeds those of some famous commercial NLO crystals. This result demonstrates that KBLABF is suitable for high-power NLO applications. This work will establish the foundation for the future NLO applications of the KBLABF crystal.