Low phonon energy BaCl2 nanocrystals in Nd3+-doped fluorozirconate glasses and their influence on the photoluminescence properties

Nd3+-doped fluorozirconate glasses, which were additionally doped with chlorine ions, were investigated for their photoluminescence (PL) properties. Upon heat treatment of the asmade glass, hexagonal phase BaCl 2 nanocrystals are formed within the material, which undergo a phase transformation to orthorhombic BaCl2 upon annealing at a higher temperature. The glasses with hexagonal phase BaCl2 nanocrystals show an enhanced Nd3+PL in the visible spectral range. Time-resolved spectroscopy on the 4G5/2 / 2G7/2 4I9/2 transition shows that the existence of hexagonal BaCl2 nanocrystals results in a significantly longer decay time. The temperature dependence of the lifetime yielded that the enhanced PL is due to a reduced multi-phonon relaxation rate.