The microcrystals of monoclinic europium molybdate, α-Eu 2 (MoO 4 ) 3 , have been fabricated by solid-state synthesis at T = 753−1273 K for 300 h. The crystal structure of α-Eu 2 (MoO 4 ) 3 has been refined by the Rietveld method and was found to belong to the space group C2/c with unit cell parameters a = 7.5576(1), b = 11.4709(2), c = 11.5158(2) Å, and β = 109.278(1)°(R B = 3.39%). About 40 narrow Raman lines have been observed in the Raman spectrum of the α-Eu 2 (MoO 4 ) 3 powder sample. The luminescence spectra of α-Eu 2 (MoO 4 ) 3 under excitation at 355 and 457.9 nm reveal domination of induced electric dipole transition 5 D 0 → 7 F 2 and the presence of ultranarrow lines at 5 D 0 → 7 F 0 and 5 D 1 → 7 F 0 transitions.

New noncentrosymmetric double borate Rb3EuB6O12 was synthesized by solid state reaction method, and their crystallographic parameters were obtained by Rietveld analysis. This borate crystallizes in the trigonal space group R32 with cell parameters of a = 13.4604(2) Å, c = 30.7981(5) Å, Z = 15. Their structure features a three-dimensional framework composed of [B5O10] 5groups that are bridged by Eu-O polyhedra. The existence of B5O10 group in the structure was confirmed by vibrational spectroscopy. Rb3EuB6O12 melts incongruently at 1101 K. The second harmonic generation effect of Rb3EuB6O12 is 16 times higher than that of α-quartz standard. In the luminescence spectrum, the domination of a single prominent narrow line from hypersensitive 5 D0-7 F2 manifold of Eu 3+ ions is observed, while 5 D0-7 F1 manifold and ultranarrow 5 D0-7 F0 line are of comparable peak intensity. These features are explained by specific local symmetry of Eu ion within the crystal structure of Rb3EuB6O12..

Microcrystals of orthorhombic rubidium samarium molybdate, β-RbSm(MoO4)2, have been fabricated by solid state synthesis at T = 450 °C, 70 h, and at T = 600 °C, 150 h. The crystal structure has been refined by the Rietveld method in space group Pbcn with cell parameters a = 5.0984(2), b = 18.9742(6) and c = 8.0449(3) Å (R(B) = 1.72%). Thermal properties of β-RbSm(MoO4)2 were traced by DSC over the temperature range of T = 20-965 °C, and the earlier reported β ↔ α phase transition at T ∼ 860-910 °C was not verified. The electronic structure of β-RbSm(MoO4)2 was studied by employing theoretical calculations and X-ray photoelectron spectroscopy. It has been established that the O 2p-like states contribute mainly to the upper part of the valence band and occupy the valence band maximum, whereas the Mo 4d-like states contribute mainly to the lower part of the valence band. Chemical bonding effects have been analysed from the element core level binding energy data. In addition, it was found that the luminescence spectrum of β-RbSm(MoO4)2 is rather peculiar among the Sm(3+) containing materials. The optical refractive index dispersion in β-RbSm(MoO4)2 was also predicted by the first-principles calculations.

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