Luminescent properties and electronic structures of rare earth and alkaline earth borates of REBa3B9O18 (RE=Lu,Y).

The samples of LuBa3B9O18 and YBa3B9O18 have been prepared by the solid-state reaction technique at high temperature and their luminescent properties were investigated for both under x-ray and vuv excitation. It is believed that the lattice defects have played an important role on the luminescent performances of the two compounds and the thermoluminescence measurement confirmed the existence of lattice defects in them. The corresponding thermoactivation energy E is estimated to be about 0.36 eV for YBa3B9O18 and 0.24 eV LuBa3B9O18, respectively, by the total glow peak method. The electronic structure of YBa3B9O18 was calculated using the CASTEP code. The results showed that it is an insulator with a band gap of 5.3 eV. The calculated total and partial densities of states indicate that the top of valence bands is mainly built upon O 2p states and the low of conduction bands mostly originate from B 2s and 2p states. Considering the luminescent properties and electronic band structures of the two compounds, the potential applications of them are discussed. [ABSTRACT FROM AUTHOR]