White light upconversion emission and color tunability in Er3+/Tm3+/Yb3+ tri-doped YNbO4 phosphor

Er3+/Tm3+/Yb3+ tri-doped YNO phosphors were obtained by the solid-state reaction method. X-ray diffraction, Raman spectroscopy, and FE-SEM were employed for characterization of the materials, and no significant structural changes have been noticed. The materials exhibited red, green and blue (RGB) upconversion emissions under 980 nm excitation. The increase of the Tm3+ concentration reduced the blue and green UC emissions due to possible Tm3+-Tm3+ and Er3+-Tm3+ energy transfer processes, respectively. White UC emission with CIE color coordinates equal to x = 0.31 and y = 0.35 has been obtained in the YNO:0.5%Er3+2.0%Tm3+20%Yb3+ composition under 64.5 mW/cm2. The tri-doped systems presented color tunability behavior indicating that multicolor, such as white light, can be easily achieved by adjusting of the Tm3+ and Yb3+ contents.