Vacuum ultraviolet spectroscopic properties of rare earth (RE) (RE = Eu, Tb, Dy, Sm, Tm)-doped K2GdZr(PO4)3 phosphate

The luminescent characteristics of RE (RE3+ = Eu, Tb, Dy, Sm and Tm)-doped K2GdZr(PO4)3 have been investigated. The band in the range of 130–157 nm in the VUV excitation spectra of these compounds is attributed to the host lattice or PO43− group absorption and the band from 157 nm to 215 nm with the maximum at 188 nm is due to the O–Zr charge transfer transition. For Eu3+-doped sample, the relatively weak band of O2−–Eu3+ charge transfer (CTB) at 222 nm is observed and for Tb3+-doped sample, the band at 223 nm is related to the 4f–5d spin-allowed transition of Tb3+. For Dy3+- and Sm3+-doped samples, the O2−–Dy3+ and O2−–Sm3+ CTBs have not been observed, probably due to the 2p electrons of oxygen tightly bound to the zirconium ion in the host lattice. In Tm3+-doped sample, the weak O2−–Tm3+ CTB is located at 170 nm. It is observed that there is energy transfer between the host and the luminescent activators (e.g. Eu3+, Tb3+ and Sm3+) except for Tm3+.

The crystal structure of the cubic phase K2GdZr(PO4)3 consists of [(GdZr)P3O18] units, each PO43− group forms a tetrahedron and each of the Gd/Zr atoms is surrounded by six oxygen atoms to form a small distorted octahedron. The cavities in the [(GdZr)P3O18] framework contain potassium atoms with an irregular coordination.Figure optionsDownload as PowerPoint slide