Raman spectra of chillagite, wulfenite, stolzite, scheelite and wolframite were obtained at 298 and 77 K using a Raman microprobe in combination with a thermal stage. Chillagite is a solid solution of wulfenite and stolzite. The spectra of these molybdate minerals are orientation dependent. The band at 695 cm-1 is interpreted as an antisymmetric bridging mode associated with the tungstate chain. The bands at 790 and 881 cm-1 are associated with the antisymmetric and symmetric Ag modes of terminal WO2 whereas the origin of the 806 cm-1 band remains unclear. The 4(Eg) band was absent for scheelite. The bands at 353 and 401 cm-1 are assigned as either deformation modes or as r(Bg) and (Ag) modes of terminal WO2. The band at 462 cm-1 has an equivalent band in the infrared at 455 cm-1 assigned as as(Au) of the (W2O4)n chain. The band at 508 cm-1 is assigned as sym(Bg) of the (W2O4)n chain.

Raman spectroscopy of the molybdate minerals chillagite (tungsteinian wulfenite-I4), stolzite, scheelite, wolframite and wulfenite

http://staff.mbi-berlin.de/mauricio/publications/2ndWPEM2004.pdf

The optical spectroscopy of lanthanides R3+ in ABi(XO4)2 (A = Li, Na; X = Mo, W) and LiYb(MoO4)2 multifunctional single crystals: Relationship with the structural local disorder

Microwave-assisted synthesis and characterisation of divalent metal tungstate nanocrystalline minerals: ferberite, hübnerite, sanmartinite, scheelite and stolzite

Polarized Raman spectra of the oriented NaY(WO4)2 and KY(WO4)2 single crystals

NaBi(WO4)2 (NBW), NaBi(MoO4)2 (NBMo) and LiBi(MoO4)2 (LBMo) single crystals grown by the Czochralski technique have been doped up to a praseodymium concentration of in the crystal. 10 K polarized optical absorption and photoluminescence measurements have been used to determine the energy position of 32, 39 and 36 Pr3+ Stark levels in NBW, NBMo and LBMo crystals, respectively. These energy levels were labelled with the appropriate irreducible representations corresponding to a C2 local symmetry of an average optical centre. Single-electron Hamiltonians including free-ion and crystal field interactions have been used in the fitting of experimental energy levels and in the simulation of the full sequence of the 4f2 Pr3+ configuration. 300 K absorption spectra of different 2S+1LJPr3+ multiplets were determined and used in the context of the Judd–Ofelt theory and for the calculation of the 1D2-related emission cross sections of this average Pr3+ centre. Non-radiative electron relaxation from the 3P0 level feeds the 1D2 multiplet. This latter level efficiently decays radiatively to the ground 3H4 multiplet but still there is a significant rate of radiative decay to the praseodymium laser channel. For , non-radiative electric dipole–dipole Pr pair energy transfer limits the radiative yield.

https://iopscience.iop.org/article/10.1088/0953-8984/16/12/023/pdf

Optical spectroscopy of Pr3+ in M+Bi(XO4)2, M+ = Li or Na and X = W or Mo, locally disordered single crystals

The structure of the tetragonal NaBi(MoO4)2 crystal was determined. The space group is I4=S42 with cell dimensions a=5.267, c=11.565 A and Z=2. The molybdenum atoms occupy two different sites of 4 symmetry. The Na+ and Bi3+ cations are situated on two positions with different occupancy factors and are short-range ordered. The IR and Raman polarized spectra are discussed on the basis of the factor group analysis and phonon calculations. The modified Urey–Bradley force field and potential energy distribution were applied for three molecular models of local disorder. Polarization properties are explained and related to the crystal structure. © 1997 John Wiley & Sons, Ltd.

A. Lemiec

Papers

Structure and vibrational properties of tetragonal scheelite NaBi(MoO4)2