Comparative study of crystal field analysis in Pr3+ and Yb3+-doped K2LaX5 (X = Cl−, Br−) ternary halides and Yb3+-doped A3Lu(PO4)2 (A = Na+, Rb+) double phosphates. Charge transfer band observations of Yb3+-doped systems

The spectroscopic properties of praseodymium and ytterbium-doped ternary halides of K2(La,Ln)X5 (X = Cl−, Br−) type and ytterbium-doped double phosphates of formula A3Lu(PO4)2 (A = an alkali metal: Na, Rb) were presented. Absorption, emission and luminescence excitation spectra were measured at 4, 10 and 293 K in the wide spectral range (VUV–IR). Luminescence of the samples was excited using various pumping lines, including the synchrotron radiation. In the Pr3+ ion systems the Stark components determined from the absorption and emission spectra were simulated by using a phenomenological crystal field model for 4f2 configuration of the Pr3+ ion in the K2(La,Pr)X5 crystals. The difference in the emission behaviour of the ternary chloride and bromide crystals were explained basing on C.F. effect and vibrational mode in the discussed systems.For the Yb3+-doped samples the strong fundamental 2F5/2 → 2F7/2 emission in the IR range as well as the CT emission bands were observed. The influence of the host lattice on charge transfer luminescence was investigated. The temperature effect and mechanisms of the observed phenomena are discussed.