Key role of Tb3+ doping on structural and photoluminescence properties of Gd2Ti2O7 pyrochlore oxide

Pyrochlore structured compounds form a special class of ceramics as host matrices in phosphors with better luminescent properties. In the present work, the optical properties of pyrochlore oxide Gd2-xTbxTi2O7 (0 <= x <= 0.16) were investigated and linked with structural properties via examination of structural distortion produced with the doping of rare-earth element. These oxide compositions were produced through standard solid-state reaction method. The investigations using advanced characterization techniques; X-ray diffraction and Raman spectroscopy give a signature of single phasic pyrochlore structure in the synthesized samples optimized through multiple heating protocol. The diffraction patterns and Raman spectra, both were continuously being shifted towards lower 2 theta value and lower wave-number side, respectively with the doping concentration which can be interpreted by the production of defects in cationic lattice. A similar decreasing trend in particle size has been observed from W-H plot (728 angstrom to 616 angstrom) and Scanning electron micrographs (0.82 mu m-0.78 mu m) with the introduction of Tb3+ ion. The band-gap for the host matrix Gd2Ti2O7 through UV absorption pattern came out to be 2.26 eV. From photoluminescence excitation (lambda(em) = 545 nm), a broad excitation band was observed in the wavelength range 305 nm-380 nm due to the f -> d transition of 4f shell of Tb ion. Furthermore, emission spectra (lambda(ex) = 375 nm) consist of bands at 489 nm, 545 nm, 585 nm and 623 nm due to the transitions at D-5(4) -> F-7(6,5,4, and 3), respectively with doping. For an optimum doping concentration with x = 0.12, a high intensity green emission line at 545 nm came out as D-5(4) -> F-7(5) dominating transition of terbium ion. Hence, the results explore the application of Gd2Ti2O7 composition as Tb-fluorescence with the optimum doping concentration of 6%.

Automated summary

This study investigates the optical and structural properties of pyrochlore oxide Gd2-xTbxTi2O7, and finds that the doping of rare-earth element leads to structural distortion and the production of defects. With increasing doping concentration, the particle size and spectral characteristics of the compounds change accordingly.