The persistent luminescence decay curves of the CaO and SrOglasses at room temperature are presented in Fig. 4. The lumi-nescence decay curve of the 490 nm band measured at roomtemperature was found multi-exponential indicating emissionfrom more than one Eu2+site as seen in.20Independently of theMP concentration, the CaO glasses exhibit lifetimes τ1and τ2of(1.9 ± 0.05) and (13 ± 0.3) min, respectively. The SrO glassescontaining 2 and 3 wt% of MPs (x = 2% and 3%) exhibit the1E-same τ1of (1 ± 0.02) min but slightly different τ2measured at(6.3 ± 0.4) and (8 ± 0.2) min, respectively. This clearly showsthat the CaO glasses show a longer duration. The fading of per-sistent luminescence (i.e. the persistent luminescence lifetimes)of the CaO glasses is practically the same as that measuredfor the MPs alone (τ1and τ2measured at (1.5 ± 0.03) min and(12.5 ± 0.4) min, respectively). This suggests that the CaO glassmatrix does not affect the actual persistent luminescence. How-ever, the SrO glass matrix affects the lifetime. The reasons forthis are discussed below.