Luminescence and Raman study of α-Bi2O3 ceramics

Highlights: ► Influence of annealing temperature and atmosphere on the Raman spectra of α-Bi2O3. ► Cathodoluminescence (CL) spectroscopy of α-Bi2O3. Influence of annealing temperature and atmosphere. ► Assessment of α-Bi2O3 grain boundaries by spatially resolved photoluminescence. ► Correlation of CL and Raman spectra with the α-Bi2O3 defect structure. - Abstract: Cathodoluminescence in the scanning electron microscope and photoluminescence in a confocal microscope have been used to investigate the luminescence properties of the stable monoclinic α-phase of Bi2O3. Powders of this oxide have been sintered at temperatures of 500 °C and 750 °C in air or in nitrogen atmospheres. Spectra of the starting powder and of the samples treated at 500 °C show luminescence bands at 1.50 eV and 1.95 eV as well as a band at 2.1 eV, more prominent in nitrogen treated samples. Sintering at 750 °C leads to quenching of the 1.50 eV infrared emission and the formation of a broad band with emission above 3 eV. The evolution of Raman bands with the sintering treatments has also been investigated.