EPR and photoluminescence studies on lithium-potassium borophosphate glasses doped with Mn 2+ ions

Abstract

The mixed alkali borophosphate xLi 2O–(30 − x)K 2O–35B 2O 3–34.5P 2O 5 (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 Mn 2+ 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 ( θ p) 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 4T 1g → 6A 1g ground state of Mn 2+ ions.