Potential PDP phosphors with strong absorption around 172 nm: Rare earth doped NaLaP2O7 and NaGdP2O7

NaLaP2O7 and NaGdP2O7 powder samples are prepared by solid-state reactions at 750 and 600 °C, respectively, and the VUV-excited luminescence properties of Ln3+ (Ln=Ce, Pr, Tb, Tm, Eu) in both diphosphates are studied. Ln3+ ions in both hosts show analogous luminescence. For Ce3+-doped samples, the five Ce3+ 5d levels can be clearly identified. As for Pr3+ and Tb3+-doped samples, strong 4f–5d absorption band around 172 nm is observed, which matches well with Xe–He excimer in plasma display panel (PDP) devices. As a result, Pr3+ can be utilized as sensitizer to absorb 172 nm VUV photon and transfer energy to appropriate activators, and Tb3+-doped NaREP2O7(RE=La, Gd) are potential 172 nm excited green PDP phosphors. For Tm3+ and Eu3+-doped samples, the Tm3+–O2− charge transfer band (CTB) is observed to be at 177 nm, but the CTB of Eu3+ is observed at abnormally low energy position, which might originate from multi-position of Eu3+ ions. The similarity in luminescence properties of Ln3+ in both hosts indicates certain structural resemblance of coordination environment of Ln3+ in the two sodium rare earth diphosphates.