REMO₄ (RE = Y, Gd; M = Nb, Ta) phosphors from hybrid precursors: Microstructure and luminescence

In this paper, YNbO₄:0.05Tb³⁺ and GdTaO₄:0.05Eu³⁺ phosphors were chosen to study the influence of the firing temperature on the phase and morphologies using novel modified in situ chemical coprecipitation technology. Results show that until the temperature reaches 1000 °C, the formation of YNbO₄ and GdTaO₄ were realized; with the increasing firing temperatures, those samples present better crystalline structure and better morphologies. The luminescent properties of Eu³⁺ and Tb³⁺ have shown that after calcinations at 1000 °C, the intensity of Eu³⁺ and Tb³⁺ increases strongly with the increasing of the calcinations temperature, while remaining relatively unchanged at the temperatures ranging between 600 and 800 °C. Furthermore, other rare earth ion doped GdTaO₄ and Y_1−xGd_xTaO₄:5 mol% Eu³⁺ with the different yttrium content were also synthesized after calcinating at the preferable temperature using the same method. The photoluminescence of Y_1−xGd_xTaO₄:5 mol% Eu³⁺ revealed that the red emission intensity of Eu³⁺ increases with the increasing of gadolinium content, indicating that Gd ion plays an important role in the energy transfer process. Also, the concentration quenching has been studied in the GdTaO₄:Eu³⁺/Dy³⁺ systems. Moreover, the characteristic emission lines of Tb³⁺, Pr³⁺, and Er³⁺ in GdTaO₄ were observed, showing that the energy transfer process appears between host and those activators.