Optical and thermoluminescence properties of R2O–RF–B2O3 glass systems doped with MnO

Alkali fluoroborate glass systems containing manganese cations have been thoroughly investigated in order to obtain information about the structural role of manganese in such glass hosts. The amorphous phase of the prepared glass samples R2O–RF–B2O3:MnO (with R = Li and Na) was confirmed from their X-ray diffraction. From the infrared spectra of these glass systems it was concluded that the glass structure contains two group of bands; one due to trigonal BO3 units and the second due to the tetrahedral BO4 units. As manganese was introduced, replacing lithium or sodium, it acts as a network modifier and the intensity of the second group of bands increases at the expense of the first group of bands. The optical absorption spectra of R2O–RF–B2O3:MnO exhibited two conventional absorption bands; one due to Mn2+ ions and the other due to Mn3+ ions. The ESR spectra of these glasses showed a six-line hyper-fine structure centered at g = 2.01 (due to Mn2+ ions) and another signal at g = 4.3 (due to Mn3+ ions). The intensity of optical absorption bands and the ESR signal due to Mn2+ ions decreases with increasing MnO concentration indicating the conversion of Mn2+ ions into Mn3+ ions in the glass network. The thermoluminescence studies on these glass systems showed a quenching of TL output with increase in the concentration of MnO. All the obtained results were discussed on the basis of the glass structure and the conversion of Mn2+ into Mn3+ ions with increasing concentration of MnO in the glass systems.