Synthesis and luminescent properties of AGd1−Ln P2O7 (A = Rb, Cs; Ln = Ce, Eu, Tb) under VUV and X-ray excitations

Abstract AGdP 2 O 7 (A = Rb, Cs) diphosphates were obtained through solid state reactions. Besides the monoclinic β-RbGdP 2 O 7 and CsGdP 2 O 7 , the high temperature phase of RbGdP 2 O 7 , α-RbGdP 2 O 7 , was reported for the first time, which is isostructural with α-KYP 2 O 7 (S.G. Cmcm , Z = 4), and the unit cell volume of α-phase is 5.4% smaller than that of β-phase. However, no reverse α ↔ β polymorphic transition was observed. The VUV-UV and X-ray excited spectroscopic properties of undoped and Ln 3+ (Ln = Ce, Eu, Tb) doped AGdP 2 O 7 (A = Rb, Cs) were presented. Under X-ray excitation, strong cascade emission of Gd 3+ was observed in each undoped AGdP 2 O 7 samples. The Gd–Ln energy transfer is relatively weak, which is due to the large Gd–Gd distance. The energy transfer probability among Gd 3+ ions follows a sequence of CsGdP 2 O 7 2 O 7 2 O 7 , which is inversely proportional with the Gd–Gd distance.