Thermochemical and luminescent properties of the K2MgV2O7 and M2CaV2O7 (M = K, Rb, Cs) vanadates

We have studied the compounds K2MgV2O7 and M2CaV2O7 with M = K, Rb, and Cs. These vanadates melt incongruently in the range 635-717A degrees C. Cooling their decomposition products to room temperature leads to the formation of nonequilibrium phase assemblages characteristic of the corresponding oxide systems. The compounds offer broadband photo- and radioluminescence with an essentially white (to the human eye) emission spectrum. A model is proposed for luminescence centers in the vanadates, which involves the formation of defects in vanadium-oxygen groups, and an energy level diagram of the emission centers is constructed in the form of configuration curves in the harmonic oscillator approximation. The luminescent properties of these compounds suggest that they can be used as basic components of cathodo- and roentgenoluminescent screens and white-light-emitting diodes with improved color performance.