Preparation and spectroscopic properties of La2Hf2O7:Tb

Poorly crystallized La2Hf2O7 powders doped with different Tb concentrations were directly synthesized through a combustion process, using glycine as a fuel. Single-phase and well-crystallized cubic pyrochlore La2Hf2O7:Tb phosphors were obtained after calcinations at 1500 degreesC. The combustion-made powders could be easily sintered to transparent ceramic La2Hf2O7:Tb in H-2 atmosphere at 1900 degreesC. The PL excitation and emission spectra were recorded for both types of the materials. Emission spectra of both type of the materials were found to be typical for Tb3+. resulting from radiative relaxation of D-5(3) and D-5(4) levels, and the integrated emission intensity ratio of 5133 to 5D4 decreases with the increase of Tb3+ concentration due to the cross-relaxation between Tb3- ions. The excitation spectra revealed that the energy absorbed by the photoionization of Tb3+ can be transferred to the dopant much more efficiently in the transparent ceramic La2Hf2O7:Tb than in powders. (C) 2004 Elsevier B.V. All rights reserved.