Optical properties of rare earth and alkali metal double molybdates and tunstates with sheelite structure

The optical properties of monocrystals of compounds with sheelite structure of the following compositions: NaNd(WO4)2, NaLa(MoO4)2, NaLa(MoO4)2:Nd3+, β-KLa(MoO4)2, β-KLa(MoO4)2:Nd3+, Na5Nd(WO4)4, Na5Bi(WO4)4, Na5Bi(WO4)4:Nd3+ and monocrystal layers α-KLa(MoO4)2 are investigated. The transmission spectra of the given crystals are taken, the spectral dependence of their absorption coefficients on incident photon energy is presented. It is established that refractive indices of the crystals measured by the immersion, ellipsometric and spectrometric methods coincide with the measurement error limits. It is noted that among the studied compounds Na5Nd(WO4)4 has the lowest refractive index and the greatest energy gap