Three in one: a cadmium bismuth vanadate NLO crystal exhibiting a large second-harmonic generation response and enhanced birefringence†
Abstract
Inorganic nonlinear optical (NLO) crystals have attracted considerable attention due to their profound applications in laser technology. In this study, we present the synthesis of a novel cadmium bismuth vanadate crystal, Cd2BiVO6, through a spontaneous crystallization approach. The title compound, containing d0 V5+, d10 Cd2+, and stereo-active lone pair effect (Bi3+) cations, crystallizes in the non-centrosymmetric orthorhombic space group Cmc21 (No. 36), characterized by isolated [VO4] tetrahedra, twisted 1D chains [Bi2O8]∞ and pseudo-2D layers [Cd6O30]∞. Remarkably, the structural characteristics endow Cd2BiVO6 with a strong second harmonic generation response of around 1.4 × KDP (25–53 μm), and a notably enlarged birefringence of 0.127 at 1064 nm, exceeding 6 times that of the vanadate NLO crystal Li3VO4 (∼0.021). Thermophysical analyses unveil its exceptional thermal stability up to 900 °C with a commendable congruent nature. Moreover, Cd2BiVO6 features a wide transparency range, with the UV and IR cutoff absorption edges observed at 0.395 and ∼5.8 μm, respectively. Besides, the observed optical characteristics associated with the microstructure of Cd2BiVO6 are explained through electronic structure calculations.