Structural and spectral characteristics of Pr-=SUB=-1-x-=/SUB=-Lu-=SUB=-x-=/SUB=-BO-=SUB=-3-=/SUB=- orthoborates

Abstract

The structure, IR absorption and luminescence spectra of Pr0.99-xLuxEu0.01BO3 orthoborates synthesized at 970oC were studied at 0≤ x≤0.99. An increase in the concentration of lutetium leads to a sequential change of the structural state of the orthoborates. At first, the orthoborates are single-phase and have an aragonite structure (0≤ x≤0.1). Then, they become two-phase and contain the aragonite and vaterite phases (0.1<x<0.6). With a further increase in x (0.6<x≤0.8), the compounds are single-phase with a vaterite structure, then they contain the vaterite and calcite phases (0.8<x≤0.95), and, finally, they become single-phase with a calcite structure (0.95<x≤0.99). An unambiguous correspondence between the structural modification and IR spectra of these compounds was established. It is shown that the emission of Eu3+ ions is observed in samples where the concentration of europium exceeds that of praseodymium. Keywords: rare earth orthoborates, X-ray diffraction analysis, crystal structure, IR spectroscopy, luminescence spectra.