Spectroscopic properties of Mn2+ in new bismuth and lead contained fluorophosphate glasses

Abstract

Luminescence, absorption and electron spin resonance (ESR) spectroscopic measurements are performed for two new Mn2+ doped fluorophosphate glass systems containing bismuth and lead, respectively, i.e., 45Ba(PO3)2-55BiF3 and 45Ba(PO3)2-55PbF2, to elucidate the nature of dopant–ligand bonding in terms of the covalence degree of dopant–ligand bond and ligand field strength. It is found from luminescence measurements that an octahedral coordination of dopant is formed, which is the same as that in fluoroberyllate and phosphate glasses. The optical absorption measurements indicate that the position of the absorption band, 4T1g(G), is red shifted, and the Racah coefficient B is 625 and 627 cm-1, respectively, as ligand field strength increases in the order of fluoroberyllate, fluorophosphate, phosphate and silicate glasses. The hfs constant A determined from the ESR measurements is 94.33 and 92.12 Oe for two glass systems, respectively. The hfs constant A is also found to be 89.98 Oe and 94.33 Oe in the respective crystalline and glasses 45P2O5-55BiF3. In addition, the resonance observed at g≃2 in both glass systems is mainly attributed to Mn2+ ions in an environment close to octahedral symmetry distorted by agglomeration of resonant centers. It, thus, can be concluded from the ESR measurements that the degree of covalency of dopant–ligand bond in both fluoroberyllate and phosphate glasses is similar, and the crystallization of the glass leads to an increase in the degree of covalency of the ligand–Mn2+ bond.