Crystal Structure, Electronic Structure, and Luminescence of Cs2KYF6:Pr3+

The crystal structure, electronic states and VUV spectroscopic behaviour of Cs2KYF6doped with Pr3+ions have been investigated both by experimental and theoretical methods. Cs2KYF6(${\rm F}m{\bar 3}m$, Z = 4, a = 945.5(3) pm, R1all= 0.0297) crystallizes with the cubic elpasolite type of structure. The local relaxation of the activator ions in the host lattices has been calculated by the projector augmented wave method (computer code VASP). The electronic states have been calculated using a spin density functional procedure based on the atomic sphere approximation (computer code ASW). VUV spectroscopic measurements show fast 4f15d1→ 4f2emission of nanosecond duration as well as slow 4f2→ 4f2emission depending on the excitation energy which indicates the occupation of different sites in the host lattice. This assumption was verified by a recently developed quantum mechanical method. The combination of the experimental and the theoretical results show that the Pr3+ions are occupying three different sites, namely the Y3+and the Cs+site as well as the K+site.