Luminescent properties and electronic structures of rare earth and alkaline earth borates of RE Ba 3 B 9 O 18 ( RE = Lu , Y )

The samples of Lu Ba 3 B 9 O 18 and Y Ba 3 B 9 O 18 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 Y Ba 3 B 9 O 18 and 0.24 eV Lu Ba 3 B 9 O 18 , respectively, by the total glow peak method. The electronic structure of Y Ba 3 B 9 O 18 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 2 p states and the low of conduction bands mostly originate from B 2 s and 2 p states. Considering the luminescent properties and electronic band structures of the two compounds, the potential applications of them are discussed.