ESR, PL and TL studies of LiAlO2:Mn/Ce phosphor

LiAlO2:Mn/Ce phosphor was prepared by combustion synthesis. LiAlO2:Mn exhibits two thermoluminescence (TL) peaks around 150 and 3200C while LiAlO2:Ce exhibits TL peaks around 170 and 2800C. PL emission of LiAlO2:Mn consists of a peak around 500 nm when excited with 450 nm while LiAlO2:Ce shows a broad band around 400 nm when excited by 320 nm. The TL emission spectrum of LiAlO2:Mn consists of a broad band at 500 nm attributed to the 4T1 to 6A1 transitions of Mn2+ ion, indicating that Mn2+ is the luminescence centre in LiAlO2:Mn. ESR studies were carried out to identify defect centres responsible for TL peaks observed in LiAlO2:Ce. Room temperature ESR spectrum of irradiated LiAlO2:Ce phosphor appears to be superposition of at least four distinct centres. Two defect centres (centres I and II) are identified in irradiated LiAlO2:Ce phosphor and these centres are assigned to O- and F+ centres, respectively. O- centre appears to correlate with the 1700C TL peak and F+ centre appears to correlate with both 170 and 2800C TL peaks in LiAlO2:Ce