Growth, spectroscopic and thermal properties of Nd-doped disordered Ca9(La/Y)(VO4)7 and Ca10(Li/K)(VO4)7crystals

Pure and Nd-doped disordered calcium vanadate Ca10K(VO4)7, Ca10Li(VO4)7, Ca9La(VO4)7 and Ca9Y(VO4)7 single crystals with high optical quality were grown by Czochralsky technique in inert atmosphere. Their polarized absorption spectra were investigated in details. Spectroscopic parameters for Nd3+ ion were determined with Judd–Ofelt theory (J–O) and theory of f–f transition intensities for systems with intermediate or anomalously strong configuration interaction (ICI or ASCI approximation). Spectral and temporal characteristics of luminescence associated with 4F3/2→4I9/2, 4I11/2 and 4I13/2 transitions were analyzed, luminescence branching ratios and radiative lifetimes were calculated. Thermal expansion coefficients were determined for Ca9La(VO4)7 and Ca9Y(VO4)7 crystals in the directions of a and c crystallographic axes. Principal thermo-optic coefficients dno/dT and dne/dT were measured for Ca9La(VO4)7 crystal in the spectral range of 0.4–1.1 μm. The potential of disordered vanadates for laser applications was analyzed from the point of thermal effects.