Cr3+-doped Bi2Ga4O9-Bi2Al4O9 solid-solution phosphors: crystal-field modulation and lifetime-based temperature sensing

Cr3+-doped Bi2Ga4O9-Bi2Al4O9 solid-solution (SS) phosphors were fabricated to explore their possible application in fluorescence lifetime-based temperature sensing. The present samples exhibited E-2 -> (4)A(2) R-line emissions associated with T-4(2) -> (4)A(2) phonon sideband emissions of Cr3+ in the wavelength range of 600-850 nm upon the excitation of visible light. Through modifying the Al/Ga ratio in the SS hosts, the Cr3+ crystal field was easily tuned from intermediate to strong, being beneficial to modulate an energy gap between E-2 and T-4(2) thermally coupled emitting states. As a result, linearly temperature-sensitive fluorescence lifetime was achieved in the Cr3+-doped Bi2Ga4O9-Bi2Al4O9 SSs with a high Al/Ga ratio, enabling us to conveniently and accurately determine a temperature with a high relative sensitivity of 2.13-3.26% K-1. (C) 2017 Optical Society of America