Widely dual tunable visible and near infrared emission in Pr3+-doped yttrium tantalate: Pr3+ concentration dependence on radiative transitions from 3P0 to the 1D2

Abstract

A dual tunable visible (reddish, orangish, blueish and white emission) and near infrared energy conversion in Pr3+-doped yttrium tantalate prepared by sol-gel method were observed depending on the ratio of radiative transitions from the 3P0 and 1D2 excited states. The Pr3+ concentration influences the crystallization process of cubic Y3TaO7 and monoclinic M’-YTaO4 crystalline phases as attested by X-ray diffraction and Raman spectroscopy. Increasing the lanthanide concentration, the Y3TaO7 crystalline phase is stabilized, delaying the formation of the M’-YTaO4 one. Spectroscopic studies revealed a pronounced near-infrared (NIR) emission of Pr3+ ions, ascribed to 1D2→3F3,4 transition, under ultraviolet (UV) and visible excitation. Changes in the emission profile were also noticed and could be correlated with the crystalline structure. A reduced multiphonon relaxation from the 3P0 to the 1D2 was observed due to the low phonon energy of the host. An intense blue emission (3P0→3H4) was detected, which is increased in comparison to the red emission, for higher dopant concentration. Samples containing the highest Pr3+ concentration (5.0 mol %) exhibited a luminescence quenching on the visible and NIR transitions from the 1D2 level indicating the influence of a cross-relaxation process on depopulating the 1D2 level and tuning the color emission. All the above-mentioned structural and luminescent properties make these yttrium tantalates potential candidates for Photonic applications, especially as red-orange-white-blue light emitters and as energy converters for the enhancement of commercial Si solar cell efficiency.