Конверсия энергии в нанокристаллах Gd-=SUB=-2-=/SUB=-O-=SUB=-3-=/SUB=-, легированных ионами Er-=SUP=-3+-=/SUP=-

The conversion of the energy absorbed by cubic Gd_2O_3 nanocrystals doped with Er^3+ and codoped with Yb^3+ and Zn^2+ ions in a temperature range of 95–425 K is studied at various concentrations of dopants. The photoluminescence spectra confirm the ability of excitation energy transfer from the Gd^3+ ions or the matrix towards the Er^3+ ions. The population of upper excited states in the Er^3+ ions depends on the way of excitation, which cause the alterations in the probability of multiphonon relaxation from the excited states to the radiative levels. The kinetics of photoluminescence decay exhibit the possible energy transfer from anionic defects created by extra doping with Zn^2+ ions. The temperature dependences of the upconversion luminescence yield for emission lines of 560 and 660 nm are found to be different.

Люминесценция примесных Ce-=SUP=-3+-=/SUP=- центров в кристаллах KH-=SUB=-2-=/SUB=-PO-=SUB=-4-=/SUB=-:Ce

The photoluminescence, X-ray luminescence, and cathodoluminescence spectra of KH_2PO_4 : 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 Ce^3+ 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 KH_2PO_4 : 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 Ce^3+ centers.

Eu2+-doped CsBr photostimulable X-ray storage phosphors — analysis of defect structure by high-frequency EPR

Eu 2+-doped CsBr in form of needle image plates is a promising alternative to the granular Eu 2+: BaFBr X-ray storage phosphor with respect to photo-stimulated luminescence, yield and spatial resolution. However, in order to understand the corresponding mechanisms on an atomic scale, the defect structure of Eu 2+-doped CsBr photostimulable X-ray storage phosphors has to be analyzed. By means of high-frequency electron paramagnetic resonance (EPR) spectroscopy, three types of defects have been observed — an electrically neutral dimeric [Formula: see text] defect complex and a neutral trimeric [Formula: see text] defect complex (FZ-center), as well as acceptor-type F-centers [Formula: see text] that are generated by the trapping of electrons at initially neutral bromine vacancies.