Optical studies of the partially disordered crystals langasite (La_3Ga_5SiO_(14)) and langatate (La_3Ga_(5.5)Ta_(0.5)O_(14)) doped with Eu~(3+)

摘要

We analyze, using the fluorescence spectroscopy of Eu~(3+), two partially disordered crystals from the langasite family: langasite and langatate. There are two main differences between these crystals: (a) the randomly occupied positions (Ga~(3+) - Si~(4+) in tetrahedral positions for langasite and Ga~(3+) - Ta~(5+) in octahedral positions for langatate) and (b) the charge difference between the ions in these positions (le for langasite and 2e for langatate). For LGS:Eu, the presence of multiple fluorescent centers could not be evidenced, while for LGT:Eu the splitting of the fluorescence lines clearly indicates the presence of multiple fluorescent centers.