VUV spectroscopic properties of rare-earth (RE3+ = Eu, Tb, Tm)-doped AZr2(PO4)3 (A+ = Li, Na, K) type phosphate

Abstract

The excitation spectra of pure and rare-earth (RE3+ = Eu, Tb, Tm)-doped AZr2(PO4)3 (A+ = Li, Na, K) in the vacuum ultraviolet (VUV) regions are investigated. The results indicate that these samples show strong absorption in the VUV range. The band ranging from 130 to 160 nm is due to the absorption band of host lattice or PO4 groups; the band at 160–200 nm is related to the charge transfer (CT) transition of O–Zr. For Eu3+-doped samples, the weak band in the excitation spectra at about 208 nm is related to the CT band of O2−–Eu3+. As for Tb3+-doped samples, the strong band at 225 nm and the weak band at 261 nm in the excitation spectra are assumed to the spin-allowed and spin-forbidden f–d transitions (4f8→ 4f75 d1) of Tb3+. However, there is no obvious band of CT of O2−–Tm3+ in the Tm3+-doped samples.