Towards guided metallic ions migration in network glass-formers: The Positronics approach in application to lithium tetraborate glass

The Positronics approach grounded on positron annihilation lifetime spectroscopy treated in terms of x3-x2-CDA (coupling decomposition algorithm) is used to recognize nanostructurization-driven volumetric effects in lithium tetraborate glass g-Li2B4O7 under transition to crystalline state, doping by Ag and/or Gd activators and 2-h above-Tg annealing in air environment. Lithium vacancies and vacancy complexes are shown to be principal free-volume elements responsible for positron trapping and decaying of bound positron-electron (positronium, Ps) states in these glasses. Expected devitrification (glass-to-crystal) transition corresponds to direct (Ps-to-positron) trapping conversion in volume-contracted network due to transformation of Ps-hosting sites in positron traps.