Optical Properties of Molybdates Containing a Combination of Rare-Earth Elements

— We have synthesized new molybdates, Cs 2 LnZrTi(MoO 4 ) 6.5 (Ln = Eu + Yb, Eu + Dy, and Gd + Dy lanthanides), containing pairs of rare-earth elements in the ratio 1 : 1. The synthesized compounds have been shown to be single-phase and isostructural with each other. We have determined their crystallographic characteristics and assessed their thermal stability. In the dysprosium-containing molybdates, the Dy 3+ luminescence intensity is low as a result of concentration quenching. The molybdate containing the Eu + Dy pair of rare-earth elements shows predominant high-intensity luminescence in the red spectral region. In addition to usual infrared emission due to ytterbium, the Eu + Yb compound demonstrates emission in the ultraviolet spectral region. We have measured luminescence decay kinetic characteristics at the peak emission wavelengths. In the case of the molybdate containing the Eu + Yb pair of rare-earth elements, energy transfer from europium ions to ytterbium has been observed. We have demonstrated high-intensity luminescence that can be excited both on intraconfigurational transitions and in the region of charge transfer bands of oxygen–molybdenum complexes.