Bi3+ Luminescence in ABiO2Cl (A = Sr, Ba) and BaBiO2Br
Trivalent bismuth luminescence is reported in three Sillen bismuth oxyhalide phases, SrBiO2Cl, BaBiO2Cl, and BaBiO2Br. These compounds exhibit Bi 6s6-> 6 s2 emission under UV and X-ray radiation. At room temperature, BaBiO2Cl shows the most intense light emission, with spectral and decay properties similar to those found in Bi4Ge3O12 (BGO). At low temperatures, each phase show an increase in the photoluminescence intensities and a narrowing of the emission peaks. In contrast to the temperature dependence of BGO, X-ray excited luminescence intensities of all three phases remain relatively constant throughout the temperature range 10 - 295 K. This result indicates that the Sillen phases undergo less thermal quenching than BGO. The low temperature and room temperature radio-luminescence decay times were determined from pulsed x-ray measurements. At room temperature, SrBiO2Cl exhibits faster decays than BGO, while, BaBiO2Cl and BaBiO2Br have decay times similar to BGO.