Influence of Al3+ co-doped ions for the improvement of orange-reddish light emitting photoluminescence characteristics of Gd2Ti2O7:Eu3+ pyrochlore

Abstract

Series of Al3+ doped Gd1.92Ti2-xO7:Eu0.08Al3+x (where x = 0, 0.02, 0.04, 0.06, & 0.08), powdered samples had been successfully developed using the solid-state reaction strategy. The purity of the produced samples was confirmed using X-ray diffraction analysis, while through Raman spectroscopy analysis and deconvolution, it has been observed that high intensity vibrational bands exhibited a blue shift (from 312.3 to 313.9 cm−1 and 518.2–518.6 cm−1) upon the introduction of Al3+ substitution in the Gd1.92Eu0.08Ti2O7 host lattice. Photoluminescence excitation spectra showed absorption in the ultraviolet & near-ultraviolet regions for Gd1.92Eu0.08Ti2O7, monitored at a wavelength of 588 nm. On the other hand, the Al3+ doped Gd1.92Eu0.08Ti2O7 oxides exhibited distinct absorption bands in 250–500 wavelength region, in addition to the host excitation bands. Under 322 nm excitation, the Al3+ doped Gd1.92Eu0.08Ti2O7 pyrochlore oxides displayed a dominant orange-reddish emission spike at 588 nm occurring due to 5D0→7F1 transition, along with weak emission peaks at 612 nm originating from 5D0→7F2 transition of trivalent europium ions. Similarly, under 394 nm excitation, the whole series exhibited analogous emission spikes, with the highly intense peak centered at 588 nm and weak band at 612 nm but in this case the emission intensity for all the peaks are relatively low as compared to when excited to 322 nm. The energy transfer processes and their relative possible reasons for concentration quenching above a Al3+ ion concentration of 2.0 mol% were discussed in detail. The optimized sample showed CIE chromaticity coordinates of (0.605, 0.392) under 322 nm excitation, indicating its positioning in the orange-reddish region. The CIE coordinates measured, depends on the emission profile under 322 nm excitation closely matched those of the economic phosphor Y2O2S:Eu3+ (x = 0.622 and y = 0.351). Overall, these results highlight the potential of Al3+ doped Gd1.92Eu0.08Ti2O7 pyrochlore oxides as orange-reddish emitting components for luminescent devices.