The Peculiarities of the Spectral Characteristics of Different Lu 1 – x RE x BO 3 Structural Modifications

The structure, the IR absorption spectra, and the luminescence spectra of microcrystals of orthoborates Lu 1 – x Eu x BO 3 , Lu 0.99 – x Tb x Eu 0.01 BO 3 , and Lu 0.99 – x Y x Eu 0.01 BO 3 with 0 < x < 0.25 synthesized at 970°C have been studied. An increase in x leads to a sequential change in the structural state of the orthoborates. At x ≤ 0.07–0.1, the compounds form the solid solution with the calcite structure and the microcrystal sizes 8–20 μm, then they become two-phase: the vaterite phase appears along with the calcite structure. At x ≥ 0.2–0.25, a whole sample volume has the vaterite structure. It is found that there is correlation between the structure and the spectral characteristics of these compounds. The luminescence spectra are studied at various wavelengths of the exciting light, which allowed the obtainment of the information on the structure of the near- surface layer and the bulk of microcrystals of these samples. The vaterite phase is shown to form both in the coarse microcrystal bulks (8–20 μm), and as fine microcrystals (1–2 μm).