Electron spin-resonance study on Ce3+ in BaLiF3

Three distinct Ce3+ sites in BaLiF3 crystals estimated from the optical spe ctra are associated with configurations of Ce3+ accompanied by different ch arge compensators. This assignment is consistent with the electron spin-res onance (ESR) result that there are two tetragonal Ce3+ centres distorted al ong the [001] axis and two orthorhombic Ce3+ centres distorted along the [1 10] axis in the absence of the cubic centre. The configurations of the Ce3 centres correspond to the substitution for Ba2+ ions along the [001] and [ 110] axes with Li+ ions and the Ba2+-ion vacancies along the [001] and [110 ] axes. The dominant component of the Ce3+ luminescence spectrum with the p eak at similar to 320 nm and the large Stokes shift energy (similar to 8300 cm(-1)) is assigned as due to the substitution for a Ba2+ ion along the [0 01] axis with a Li+ ion. As the ionic radius (0.74 Angstrom) of Li+ is much smaller than that (1.60 Angstrom) of Ba2+, the Li substitution produces mo re space, resulting in the large lattice relaxation in the 5d excited state of Ce3+.