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

In this paper, YNbO4:0.05Tb(3+) and GdTaO4:0.05Eu(3+), 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 degrees 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 degrees 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 degrees C. Furthermore, other rare earth ion doped GdTaO4 and Y1-xGdxTaO4:5 mol% Eu3+, with the different yttrium content were also synthesized after calcinating at the preferable temperature using the same method. The photoluminescence of Y1-xGdxTaO4:5 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.