EPR and FT-IR spectroscopic studies of B_2O_3-Bi_2O_3-MnO glasses

摘要

EPR and FT-IR absorption measurements performed on xMnO centre dot (100 - x)[B_2O_3 centre dot Bi_2O_3] glasses with 0 < =x < = 50 mol percent are reported. The EPR spectra of all investigated samples exhibit resonance signals that are characteristic for the Mn~(2+) ions. For x < =20 mol percent the spectra consists of two resonance lines centered at g_(eff) approx = 4.3 and g_(eff) approx = 2.0, their relative intensity depending on the manganese content of the sample. For x < = 3 mol percent, the line from g_(eff) = 4.3 has a resolved hyperfine structure characteristic for isolated Mn~(2+) ions disposed in distorted sites of an octahedral symmetry. The resonance line centered at g_(eff) approx = 2.0 has not hyperfine structure and is attributed to coupled Mn~(2+) ions by dipolar (x < = 5 mol percent) or/and superexchange interactions (x > 5 mol percent). The FT-IR data indicate the presence in the glasses of the BO_3 , BO_4, BiO_6 and BiO_3 units and its dependence on the MnO content.