EPR and photoluminescence studies on lithium-potassium borophosphate glasses doped with Mn2+ ions

The mixed alkali borophosphate xLi2O–(30 − x)K2O–35B2O3–34.5P2O5 (5 ≤ x ≤ 25) glasses doped with 0.5 mol% of manganese ions have been studied using EPR and photoluminescence techniques. The EPR spectra of all the investigated samples exhibit resonance signals which are characteristic of Mn2+ ions. The resonance signal with effective g value at g = 2.02 exhibits a six line hyperfine structure. The zero-field splitting parameter (D) at room temperature has been evaluated from the intensities of allowed hyperfine lines. The EPR spectra at different temperatures (123–295 K) have also been studied. It is found that the spin concentration (N) exhibits non-linear behaviour with composition showing the mixed alkali effect (MAE). From the EPR data, the paramagnetic susceptibility (χ) has been calculated at various temperatures. The Curie constant (C) and paramagnetic Curie temperature (θp) have been evaluated from the 1/χ versus T graph. The photoluminescence (PL) spectrum exhibits a green emission band at 582 nm and this band has been assigned to a transition from the upper 4T1g → 6A1g ground state of Mn2+ ions.