Résumé
Crystals of the barium molybdates BaKYb(MoO4)3 and BaMoO4 were obtained by spontaneous nucleation from high-temperature flux experiments. The compounds were characterized by energy-dispersive spectrometry (EDS) and Raman spectroscopy, and their structure was solved from single-crystal X-ray diffraction data at room temperature. BaMoO4 crystallizes in the tetragonal I41/a symmetry with a = b = 5.5723(4) and c = 12.7954(9) Å. With the scheelite-type structure, BaMoO4 displays sharp and intense lines in its FT-Raman spectrum registered at room temperature. The new triple molybdate BaKYb(MoO4)3 is described in a monoclinic lattice C2/c of parameters a = 17.3517(5), b = 12.1477(4), c = 5.2481(2) Å, = 105.344(2)°. The Yb 3+ ions are surrounded by oxygen leading to YbO8 coordination polyhedra while atomic disorder is observed for the cations Ba 2+ and K + , statistically sharing their positions inside 8-vertex coordination polyhedra. The Raman spectrum confirms the presence of distorted MoO4 tetrahedra for the BaKYb(MoO4)3 molybdate. Investigation of its magnetic properties was undertaken in order to check whether a magnetic ordering occurs at low temperature.