New Nanosized Luminophores Obtained via Evaporation of REE Silicates and Germanates

Resumo

Nanophosphors in the amorphous state are first obtained via pulsed electron beam evaporation of targets made of polycrystalline phosphors with the compositions Ca₂M₈(SiO₄)₆O₂:Eu (M = Y and Gd) and Ca₂La₈(GeO₄)₆O₂:Eu with the structure of oxyapatite. Reduction of ions Eu³⁺ → Eu²⁺ in the electron beam is found. Modification of the Raman scattering (RS) spectra of the samples in the case of a decrease in the size of the particles from bulk to a nanosized state is found. The change in the forbidden band width E_g of the samples in the case of transition from a bulk powder to an NP is considered. The spectral and luminescence characteristics of the samples in the polycrystalline and nanoamorphous states are studied. It is shown that, in the case of transition to nanosamples, the ligand field around Eu²⁺ changes. This may be due to the violation of the translational symmetry in the NP. The bond between the 4f and 5d electrons weakens. Degeneracy of the ²e_g level appears. Presumably, the reduction of ions Eu³⁺ → Eu²⁺ in the electron beam due to the breaking of the Si(Ge)–O bond in the process of evaporation of the samples and capture of the released electron by the Eu³⁺ ions is found.