Single crystals of K5LaLi2F10:Er3+ and K5LaLi2F10 were synthesized and the
structural determination was made by x-ray diffraction analysis. The struct
ure is orthorhombic with space group Pnma. The unit cell parameters are: a
= 20.775, b = 7.822 and c = 6.963 Angstrom. The infrared transmission and R
aman scattering spectra of oriented single crystals were measured and discu
ssed in terms of factor group analysis and x-ray structure. A vibrational a
ssignment is proposed. Preliminary optical properties of Er3+ ions in K5LaL
i2F10 crystals have been investigated using absorption, luminescence and li
fetime measurements in the 5-300 K temperature range. The low temperature a
bsorption and luminescence spectra of EPC have allowed us to identify the S
tark levels of low-lying multiplets. The luminescence observed at 5 K has b
een attributed to the S-4(3/2) --> I-4(15/2) (18300 cm(-1)), F-4(9/2) --> I
-4(15/2) (15000 cm(-1)), S-4(3/2) --> I-4(13/2) (11800 cm(-1)) and I-4(11/2
) --> I-4(15/2) (10000 cm(-1)) transitions. The lifetimes of selected excit
ed states were measured at 5 and 300 K temperature. The obtained data gave
the first insight into the luminescent properties of Er3+ ions in the fluor
ine surroundings in K5LaLi2F10 crystals.