Structural and Optical Characterization of Ytterbium Doped Lutetium Double Phosphates

Powder samples of the ternary phosphates A3Lu(PO4)2:Yb3+ (A = Na, Rb) have been synthesised by solid state reactions. The spectroscopic properties of Yb3+ in double phosphate host lattices were investigated using absorption, emission and excitation spectra at 4, 10 and 293 K in the VUV to IR range. The results obtained for both types of phosphates are compared. Together with the fundamental 2F5/2 2F7/2 emission in the IR range, a broad band emission with two peaks in the UV region were observed in Yb3+-activated Na3Lu(PO4)2. The second emission is due to a charge–transfer transition type. The influence of the alkali metal cation site of the host lattice on the luminescence properties was investigated. The tentative energy level scheme of the ground and excited 2FJ (J=7/2, 5/2) levels is described.