Photo-luminescence studies of strontium barium niobate crystals doped with Cr3+ ions

This paper reports the photo-luminescence spectroscopic results of Strontium-Barium-Niobate, Srx,Ba1−xNb2O5 (SBN, x = 0.61 for near congruent composition) crystals doped with Cr2O, at cryogenic temperature (20 K). The experimental results reveal the need of re-assignment of the Cr3+ ions defect centres in this material. For first time, a broad emission band in the near infrared region centred at ca. 950 nm is reported. This emission band has micro-seconds decaytime constant and a FWHM band-width > 1700 cm−1 and has been ascribed to the vibronically assisted 4T2 → 4A2 transition. A much narrower emission band centred at ca. 764 nm with milli-seconds decaytime constant and a FWHM band-width of ca. 170 cm−1 is correlated to the 2E → 4A2 radiative transition (R-line).