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The luminescent nanocrystalline KEu(WO4)2 and KGd0.98Eu0.02(WO4)2 have been prepared by the Pechini method. X-ray diffraction, infrared and Raman spectroscopy as well as optical spectroscopy were used to characterise the obtained materials. The crystal structure of KEu(WO4)2 was refined in I2/c space group indicating the isostructurality to KGd(WO4)2. The size of the crystalline grains depended on the annealing temperature, increasing with the increase of the temperature. The average size of crystallites of both crystals formed at 540 °C was about 50 nm. Vibrational spectra showed noticeable changes as a function of size due to, among others, phonon confinement effect. Luminescence studies did not reveal significant changes for the nanocrystallites with the lowest grain size in comparison with the bulk material. The differences observed in luminescence spectra in form of slight inhomogeneous broadening of the spectral lines and increase of the hypersensitive I0–2/I0–1 ratio point to very low symmetry of Eu3+ ions and change of the polarisation of the local vicinities of Eu3+. X-ray diffraction, vibrational and optical studies showed that the structure of the synthesised nanocrystalline KEu(WO4)2 and KGd(WO4)2:Eu is nearly the same as that found for the bulk material. The size-driven phase transitions were established for both compounds.

Crystals of NaMg3Al(MoO4)5 doped with 0.5% Cr3+ ions have been synthesized and characterized by a single-crystal X-ray structure analysis and IR, Raman, electron absorption and luminescence spectroscopic studies. It has been shown that NaMg3Al(MoO4)5 crystallizes in the P 1 ¯ structure, with a=6.8744(8) A, b=6.9342(7) A, c=17.605(2) A, α=87.788(8)°, β=87.727(9)°, γ=78.501(9)°, Z=2. The characteristic feature of the structure is its enormously large thermal displacement parameter for sodium, even at 105 K. The IR and Raman spectra indicate significant interactions between the MoO42− ions in the structure. The electron absorption, excitation and luminescence studies have shown that there are at least two different sites of incorporated Cr3+ ions in the NaMg3Al(MoO4)5 crystal structure. They differ themselves by strength of crystalline field. One of them is characterized by Cr3+ in low ligand field and 4T2→4A2 emission whereas the second is characterized by higher strength of the crystal field and dominant 2E→4A2 emission. Temperature-dependent studies show that the compound does not exhibit any phase transition.

IR, Raman, X-ray, electron absorption and luminescence studies have been performed for novel laser Nd 3 BWO 9 and Eu 3 BWO 9 borotungstates exhibiting non-centrosymmetric crystal structures. The assignment of observed vibrational modes to respective symmetry and vibrations of atoms has been proposed. These studies have shown that vibrational and electronic properties of these crystals can be better explained when P 6 3 symmetry is assumed, instead of previously proposed P 3 one. The crystal structure refinement has also confirmed that symmetry of the Eu 3 BWO 9 borotungstates is P 6 3 , not P 3.