EPR study of the CaF2 powder mechanochemical doping with rare-earth ions

In the present work we show with electron paramagnetic resonance (EPR) spectroscopy that in the process of the mechanochemical doping of the CaF2 fine particles with Er3+ and Yb3+ ions the cubic symmetry rare-earth (RE) ion centers are formed with the concentration proportional to the particles surface in the sample. Amount of the mechano-doped RE-ion centers is proportional to ηα, where η is the weight fraction of the RE fluoride in the initial mixture and α ~ 0.8. Cubic symmetry centers dominate in the EPR spectrum up to η = 0.1. A hypothesis of the cubic RE-ion center formation is proposed according to which its origin is associated with the presence of the ideal cleavage planes in the CaF2 crystals: during the mechano-doping a considerable fraction of the rare-earth ions is trapped between the cleavage planes of the agglomerating particles, thereby getting into the crystal field of the cubic symmetry. © Kazan Federal University (KFU)