Electron paramagnetic resonance and magnetic circular dichroism of Gd3+ ions in oxyfluoride glass–ceramics containing CaF2 nanocrystals

Crystalline phase detection in glass ceramics by EPR spectroscopy

“…At high concentration, various forms of composite defects such as gadolinium ion pairs and clusters may also be present. Gd 3+ in oxyfluoride glass ceramics containing fluorite structure crystalline phase have been studied recently [19,20]. Main results for compositions containing CaF 2 , SrF 2 and BaF 2 are summarized in Fig.…”

“…7. When Gd 3+ replaces the similarly sized Ca 2+ ions in glass ceramics containing CaF 2 , the EPR spectrum is dominated by Gd 3+ in local cubic symmetry crystal field [19], whereas substitution of significantly larger Ba 2+ ions in glass ceramics containing BaF 2 leads to an EPR signal characterized by SH parameters for trigonal site symmetry [20]. To summarize, EPR spectral features of Gd 3+ ions are sensitive to the local environment and are effective for detecting the presence of crystalline phase in glass ceramics.…”

“…Absorption and luminescence spectra, on the other hand, can indicate changes in the local environment around the luminescence centres, however, structure sensitive magnetic resonance spectroscopy techniques should be employed to reveal the detailed nature of defects in glass ceramics. Electron paramagnetic resonance (EPR) is one of the most convenient and informative methods for the study of point defects in crystals and glasses [1][2][3][4][5][6][7][8][9][10][11], however, there has been only a limited number of applications to glass ceramics [12][13][14][15][16][17][18][19][20][21].…”

Optical detection of paramagnetic centres: From crystals to glass-ceramics

“…The EPR spectra of the Gd 3+ centres in glasses are typical of lowsymmetry centres and the EPR is therefore broadened over a whole magnetic field range. On the contrary, the EPR of glass-ceramics showed spectra of the cubic Gd 3+ centres with well resolved fine structure [21]. The same Gd 3+ spectrum but without so good resolved fine structure has been detected also in the oxyfluoride glass-ceramics (see Fig.…”

“…6, based on [21]). Therefore, the MCD-EPR technique allows to find out a direct correlation between the cubic Gd 3+ centre and its MCD, but a similar MCD in the glasses could be attributed to the low-symmetry Gd 3+ centres [21].…”