Modifications of Light Emission Spectra and Atomic Structure of Europium Molibdate Bulk Crystals Caused by High Pressure and Heat Treatment

Essential enhancement of light emission ability of europium molybdate - Eu
₂
(MoO
₄
)
₃
(EMO) crystals has been achieved by combined application of high pressure (9 GPa) and heat treatment (a procedure was repeated from 3 to 25 times for different samples). Multifold increase in light emission of EMO single crystals can be achieved, without deterioration of the optical transparency of the material. Simultaneously the light emission spectra change substantially. Nature of this phenomenon is explained by the modifications of the crystal field caused by structural transformations induced by the treatments. These modifications of the crystal fields bring to increase in probability of light emission optical transitions between 4f sublevels of europium ions.