Energy Transfer of Electronic Excitations by Activators in Phosphates and Sulfates via the Creation of Combined Electron Emission States

Abstract

In this work, the mechanisms for creating a combined electronic–radiative local state beneath the conduction band, consisting of intrinsic and activator electron–hole states, are experimentally substantiated. In the first part of this work, the mechanisms of the formation of intrinsic and activator electron–hole trapping centers are experimentally demonstrated in all four matrices with activators. Intrinsic electronic states are localized on activators and anions of the matrix, forming intrinsic and activator electronic states. The hole component of the electron–hole pairs is localized near the activators. Thus, the energy of intrinsic electronic excitations localized in the matrix in the form of combined electronic– radiative states is observed at 3.06–3.1 eV and 2.92–2.95 eV. Radiative states are excited by photon energies of ~4.5 eV and ~4.0 eV, resulting in recombination emissions at 3.06–3.1 eV and 2.92–2.95 eV, as well as activator emissions at 2.06 eV for Mn2+, 2.5 eV for Tb3+, and 2.56 eV and 2.16 eV for Dy3+. Energy transfer from the matrix to emitters or activators occurs during the decay of the combined radiative state. Upon heating, electrons localized on anions and activators delocalize at temperatures of 200–350 K. The energy released during the recombination of an electron with a hole near the activators is transferred to the activators. This process facilitates energy transfer to activators in dosimeters and detectors.