Crystal structure, phonon and luminescence properties of AgRE(WO4)2 tungstates, where RE = Y, Pr, Nd, Sm - Lu

The crystal structure of the all studied compounds was refined in the monoclinic C2/m (C-2h(3)) space group. The IR and Raman spectra of polycrystalline AgRE(WO4)(2) have been recorded and analysed using the factor group approach. In the theoretical considerations the C2/m, P2/c and C2/c unit cell structures were taken into account. The change of the unit cell parameters induced by the RE ions exchange has been analysed. The assignment of the observed bands to the internal and external modes has been proposed. The verification of the structure has been done on the basis of the vibrational behaviour of the studied tungstates. Absorption, emission and excitation spectra of the investigated AgRE(WO4)(2) polycrystals have been measured and analysed. The luminescence decay times of D-5(0) -> F-7(2) (Eu3+) and D-5(4) -> F-7(5) (Tb3+) transitions have been calculated. (c) 2018 Elsevier B.V. All rights reserved.