Transparent Ceramics Research Center, SICCAS
Key Laboratory of Transparent Opto-fuctional Inorganic Materials, CAS
Eu2+ stabilization in YAG structure
Dr. Eva Mihokova
Institute of Physics, Czech Academy of Sciences, Prague, Czech Republic
A set of Eu-doped Y3Al5O12 (YAG) phosphors in the powder form was synthesized by multiple-step solid state reaction under the reducing Ar:5%H2 atmosphere. We investigate their physical properties by means of X-ray diffraction, time-resolved luminescence spectroscopy and electron paramagnetic resonance (EPR). Our focus is put on well-grounded confirmation of Eu2+ occurrence in the YAG structure.
X-ray diffraction confirmed the presence of major YAG phase in all samples. We study the influence of Eu concentration, form of doping (EuS, EuF2 or Eu2O3) and a number/form of annealing steps. Corresponding characteristics were measured and evaluated in a broad temperature range (8 – 800 K). The correlated measurements show that the single Eu2+ ions stabilized in YAG in the yttrium position are responsible for the 440 nm emission. The corresponding lowest energy excitation band is situated at 300 nm and the radiative lifetime of Eu2+ emission is about 500 nanoseconds. Phenomenological model of excited state dynamics was used to explain the experimentally observed features. We also study the presence od trapping centers in YAG:Eu samples by thermally stimulated luminescence and evaluate their principal characteristics. We discuss possible practical exploitation of Eu2+ center in the YAG host.
Dr. Eva Mihokova is a leading senior scientist in the Institute of Physics, Czech Academy of Sciences in Prague Czech Republic. She studied at the faculty of Mathematics and Physics of the Charles University in Prague, Czech Republic where she received her Master degree. She received her PhD degree in the Institute of Physics Czech Academy of Sciences in Prague Czech Republic. In last years, Eva Mihokova studies optical properties of scintillating materials with wide spectrum of applications. Her research focuses on processes related to luminescence and scintillation mechanisms, their interpretation and numerical modelling. Within methods of characterization of material systems in the form of single crystals, nanopowders and nanocomposites she specializes particularly in investigation of defects and trapping centers by thermally stimulated luminescence technique.
She is an author and coauthor of about 200 scientific papers in international peer-reviewed journals and 1 book chapter. Her publications received more than 3700 citations (excluding selfcitations), H index 33. She was a principal investigator in about 10 domestic and international projects and a research team member in about other twenty. She was awarded the Prize of Academy of sciences of the Czech Republic for excellent scientific results, “PbWO4 single crystals- scintillator for high energy physics. Physical description and material optimization” and The Prize of “Otto Wichterle” of the Academy of Sciences of the Czech republic.