SYNTHESIS OF NEW PHOSPHORS BASED ON Tm3+, Nd3+ OR Ho3+ DOPED GERMANATES BY “WET” CHEMICAL ROUTES

Various “wet” synthetic chemical techniques are widely used for the production of multifunctional inorganic materials. In contrast to the standard high-temperature solid state route, methods based on the dissolution of starting reagents allow one to obtain phases with given particle morphology and particle size distribution. Besides, with this approach, the defect structure can be efficiently controlled by varying the synthesis conditions and solution preparation. These advantages are important for producing luminescent materials.This work was supported by the Russian Science Foundation, project № 16-13-10111

Crystal structure of a new HfO(OH)2 oxyhydroxide

The crystal structure of a new hafnium oxyhydroxide obtained by an ion-exchange reaction from a Li2HfO3 precursor has been solved by a direct method and refined using Rietveld full profile fitting based on X-ray powder diffraction data. HfO(ОН)2 crystallizes in a P21/c monoclinic unit cell (a = 5.5578(5) Å, b = 9.0701(10) Å, c = 5.7174(5) Å, β = 119.746(5)°); its structure can be described as a framework formed by edge-sharing HfO6 octahedra connected to each other via vertices. In addition, an analysis of the atomic pair distribution function obtained using synchrotron radiation was used to confirm the model and to describe fine-structure features

Photo - and radioluminescence of lithium hafnate Li2Li_{2}HfO3O_{3}

Photoluminescence, excitation and pulse cathode luminescence spectra, and decay kinetics of lithium hafnate Li 2HfO 3 were investigated at temperatures 300 and 7.5 K. Time-resolved luminescence spectra were excited with synchrotron radiation in UV-VUV range. Strong emission with the peak position at 4.42 eV and with the decay time in μs range was revealed at T = 7.5 K. The emission was attributed to radiative decay of self-trapped excitons (STE). The features observed in the excitation spectra at 6.6 eV were likely to take place because of the exciton formation, with inter-band transitions dominating at 6.7 eV. Crystal structure defects underpin the luminescence spectra formation at room temperature in the frame of vacancy model. © 2012 Elsevier B.V. All rights reserved