Effect of Microstructure on Photo-Induced Current Characteristics of Eu 2+ -Doped SrAl 2 O 4 .

Research interest is active in Eu 2+ /Dy 3 -doped SrAl 2 O 4 phosphors, and the photocurrent characteristics of Eu 2+ -doped SrAl 2 O 4 without Dy 3+ was investigated extensively. However, it exhibits a low photocurrent of ~1 μA owing to high resistance. In this study, the changes in a photo-induced current with grain size were examined. The effect of the processing methods on the microstructure and photocurrent characteristics of Eu 2+ -doped SrAl 2 O 4 phosphors was investigated. (Sr 0.99 Eu 0.01 )Al 2 O 4 powders were synthesized using a conventional solid-state method and calcined at 1350 °C under a 3% H 2 /(Ar + H 2 ) reducing gas atmosphere. Sample pellets were fabricated as conventional and hot-press-sintered bodies at 1400 °C. A thin film of the sample was deposited on an alumina substrate by radio-frequency magnetron sputtering. Scanning electron microscopy revealed that the hot-press-sintered body has larger grains than the conventionally sintered body. The photo-induced current of the hot-press-sintered body at 400 lx was ~100 and ~1000 times higher than those of the conventionally sintered body and thin film, respectively. Impedance analysis confirmed that this dramatic increase in the photo-induced current is closely related to the increase in the grain size and crystallinity of the sample. This study verifies the applicability of Eu 2+ -doped SrAl 2 O 4 as both a phosphor and photosensor.