Photoluminescence of Eu3+-activated GdTaO4 with both M type and M′ type structures

A series of Eu3+ doped M and M' type gadolinium orthotantalate Gd1-xEuxTaO4 (x = 0-0.20) have been synthesized by high temperature solid state reaction. The emission and excitation spectra for M and M' type gadolinium orthotantalate are studied in detail. The structural difference between M and M' type structure obviously influences their luminescence properties. The main excitation bands in M' type Gd1-xEuxTaO4 shift to shorter wavelength because of a shorter distance of Ta-O in comparison with M type. The strong evidence from excitation spectra, emission spectra and diffusive reflection spectra of these two system show Gd3+ can play an intermediate role of energy transfer in the process of luminescence. There is energy transfer from TaO43- to Gd3+ and finally to Eu3+ via the charge transfer states and spectral overlap. (C) 2000 Kluwer Academic Publishers.