Paramagnetic defects in gamma-irradiated Na/K-silicate glasses

Gamma-irradiated alkali silicate glasses of the variable composition 22xNa 2O · 22(1 - x)K 2O · 3CaO · 75SiO 2 have been studied using the electron paramagnetic resonance (EPR) method. It has been established that, upon the successive replacement Na → K in the two-alkali silicate glass, the EPR spectrum of hole centers on nonbridging oxygen atoms can be represented as a superposition of signals from the oxygen centers HC 1(Na), HC 2(Na), HC 1(K), and HC 2(K), which are characteristic of single-alkali silicate systems. The concentration dependences of hole and electron paramagnetic centers do not exhibit specific features that can be interpreted as a manifestation of the "mixed-alkali effect." The results obtained have been discussed taking into account the extended model of centers on nonbridging oxygen atoms. © 2012 Pleiades Publishing, Ltd