Widely dual tunable visible and near infrared emission in Pr3+-doped yttrium tantalate: Pr3+ concentration dependence on radiative transitions from P-3(0) to the D-1(2)

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 P-3(0) and D-1(2) 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 D-1(2)-> F-3(3,4) 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 P-3(0) to the D-1(2) was observed due to the low phonon energy of the host. An intense blue emission (P-3(0)-> H-3(4)) 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 D-1(2) level indicating the influence of a cross-relaxation process on depopulating the D-1(2) 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-orangewhite-blue light emitters and as energy converters for the enhancement of commercial Si solar cell efficiency. (AU)