Lanthanide doped strontium barium niobate: Optical spectroscopy and local structure at the impurity sites

Strontium barium niobate (SBN), SrxBa1−xNb2O6 single crystals and nanocrystalline powders doped with different Ln3+ ions have been obtained for various values of x. Their optical spectroscopy and Ln edge EXAFS have been investigated in detail, in particular in order to identify the classes of sites occupied by the dopant ions. Whilst Eu3+ appears to enter mainly sites with coordination number 12 in the single crystals, the smaller ion Er3+ is mainly accommodated in octahedral sites. The luminescence spectra of the nanocrystalline materials are strong and similar to the ones of the single crystals, although some broadening appears to be present. Strong green upconversion is obtained upon excitation at 800 nm for nanocrystalline Sr0.5Ba0.5Nb2O6 doped with 1 mol% Er3+.