Abstract:
CaAl12O19 powder activated with Tb ions has been
prepared by the urea combustion route. Phase evolution of the
powder is determined by X-ray diffraction techniques.
Photoluminescence emission of CaAl12O19:Tb consists of a
dominant peak at 544 nm when excited with UV radiations.
Thermoluminescence (TL) peaks at approximately 140 °C,
245 °C and 458 °C are observed in the CaAl12O19:Tb phos phor. Investigations using the technique of electron spin reso nance (ESR) were carried out to study the defect centers in duced in the phosphor by γ-ray irradiation. ESR study reveals
the presence of several distinct centers. One of the centers
(center I) with an isotropic g factor 2.0110 is tentatively
assigned to an intrinsic O− type center and this center relates
with the TL peak at 140 °C. Center II with an axially symmet ric g-tensor with principal values g∥ = 2.0324 and g⊥ = 2.0060
is attributable to an O2
− ion and also appears to correlate with
the 140 °C TL peak. Several F+
-centers have been identified
and their correlation with the observed TL peaks will be
discussed.
