Photoluminescence Spectroscopy of NaTaO_3 and NaTaO_3∶Bi~(3+) Photocatalysts

NaTaO3 and Bi3+ doped NaTaO3 were prepared by conventional high temperature solid state reactions and characterized by the photoluminescence spectroscopy. The luminescence characterization of NaTaO3 is sensitive to its preparation condition. Under the condition of Na scarcity, two luminescence bands of 515 nm and 745 nm are observed in the photoluminescence spectra, which are ascribed to the antisite defects of Ta....Na and V`Na defects, respectively. Under the condition of Na enough, the luminescence band shifts to about 460 nm, which are originated from the intrinsic tantalate groups. The introduction of Bi3+ causes the emission band shifts from 515 to 455 nm, namely, the Ta....Na defects are replaced by Bi..Na defects and the luminescence characterization of NaTaO3 is shift to the direction of a higher n(Na)/n(Ta) ratio. The present work also demonstrates that the photoluminescence spectroscopy is a powerful technique to characterize the defect chemistry in semiconductor materials and it is especially useful in the study of photocatalysts.