Luminescence of impurity Ce3+ centers in KH2PO4 : Ce crystals

Abstract

The photoluminescence, X-ray luminescence, and cathodoluminescence spectra of KH₂PO₄ : Ce single crystals contain a nonelementary band of radiation with an energy of 3.55 eV and decay time of 27–33 ns. It is formed by fast radiative interconfiguration d → f transitions between the excited and ground states of Ce³⁺ ions, with the ground state is split by a crystalline field. In the range of concentrations studied (0.5–3 × 10^–2 wt %), Ce3+ ions enter the KH₂PO₄ : Ce crystal lattice as substitution ions. Local charge compensation takes place by means of defects in the crystal structure that cause luminescence with a large Stokes shift in the region of 2.4–2.2 eV. The presence of hydrogen sublattice defects decreases the efficiency of energy transport by free charge carriers to the luminescent centers. The interaction of defects and impurity centers manifests itself as a slow inertial building-up of the stationary X-ray luminescence yield of Ce³⁺ centers.