A model of the capture volume of free carriers in fluorophosphate glasses doped with terbium

The induced electron paramagnetic resonance (EPR) and optical absorption spectra of Tb2O3 doped glasses in the LiF-MgF2-Ba(PO3)(2) System are investigated. The intensities of the doublet signals from PO42- and PO32- centers in regions with different contents of the fluoride component are determined as functions of the terbium concentration. It is shown that fluorophosphate glasses can be characterized by two values of the capture volume parameter, which differ by a factor of 5.0-6.6 depending on the dopant concentration. In the range of minimum dopant concentrations at which the capture volume is maximum, the dopant ions have a hypothetically phosphate environment. It is suggested that the capture volume parameter defined by the express sion In c/c(0) = -VC3 can be treated as a characteristic of the distribution of dopant ions in fluorophosphate glasses.