2013

TSL and fractional glow study of Ge-doped α-quartz.

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A. Zolatarjovs, A.N. Trukhin, K. Smits, D. Millers

Abstract. Crystalline α-quartz doped with 0.1wt% and 0.9wt% germanium was studied using
TSL and FGT equipment. Sample was chosen because previously it is known that Ge in quartz
is efficient trap for electrons, therefore it could be used for detection of hypothetic self-trapped
hole in α-quartz. However previous investigations of ODMR and TSL shows that in α-quartz
the hole is still mobile and trapping occurs only on defect states. The activation energies for
both TSL peaks are found by fractional glow and Hoogenstraaten method. The TSL
distribution changes depending on Ge concentration and also on irradiation type. The TSL
peaks below 70K in quartz doped with Ge could belong to hole trapped on Ge.

IOP Conference Series: Materials Science and Engineering 49 (2013) 012056

doi:10.1088/1757-899X/49/1/012056

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Photocatalytic Properties of TiO2 and ZnO Nanopowders

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L. Grigorjeva, J. Rikveilis, J. Grabis, Dz. Jankovica,
C. Monty, D. Millers, K. Smits

Photocatalytic activity of TiO2 and ZnO nanopowders is studied
depending on the morphology, grain sizes and method of synthesizing.
Photocatalysis of the prepared powders was evaluated by degradation of the
methylene blue aqueous solution. Absorbance spectra (190–100 nm) were
measured during exposure of the solution to UV light. The relationships
between the photocatalytic activity and the particle size, crystal polymorph
phases and grain morphology were analyzed. The photocatalytic activity of
prepared TiO2 nanopowders has been found to depend of the anatase-to-rutile
phase ratio. Comparison is given for the photocatalytic activity of ZnO
nanopowders prepared by sol-gel and solar physical vapour deposition
(SPVD) methods

Latvian Journal of Physics and Technical Sciences 2013, N 4

DOI: 10.2478/lpts-2013-0025

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Characterization of hydroxyapatite by time-resolved luminescence and FTIR spectroscopy

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L.Grigorjeva, D.Millers, K.Smits, Dz.Jankovica, L.Pukina

Abstract. Time-resolved luminescence and FTIR absorption spectra of undoped and Eu
and Ce doped hydroxyapatite nanocrystalline powders prepared by sol-gel method were
studied. The luminescence band at 350-400 nm was detected and two decay times (11 ns
and 38 ns) was determinated for Ce doped samples. The luminescence spectra and decay
kinetics were analized for Eu doped nanopowders. The Eu3+ ion was incorporated in
different Ca sites. The process of energy transfer to Eu3+ excited state (5D0) was detected
from luminescence decay kinetics.

IOP Conference Series: Materials Science and Engineering 49 (2013) 012005

doi:10.1088/1757-899X/49/1/012005

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Ultraviolet luminescence of ScPO4, AlPO4 and GaPO4 crystals

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Anatoly N Trukhin, Krishjanis Shmits, Janis L Jansons and
Lynn A Boatner

Abstract
The luminescence of self-trapped excitons (STEs) was previously observed and described for
the case of tetragonal-symmetry ScPO4 single crystals. The subject band in this material is
situated in the UV spectral range of 210 nm or 5.8 eV. In the present work, we are both
expanding this earlier luminescence study and seeking to identify similar luminescence
phenomena in other orthophosphate crystals, i.e., AlPO4 and GaPO4. These efforts have
proven to be successful—in spite of the structural differences between these materials and
ScPO4. Specifically we have found that for AlPO4 and GaPO4, in addition to an -quartz-like
STE, there is a UV luminescence band that is similar in position and decay properties to that
of ScPO4 crystals. Potentially this represents an STE in AlPO4 and GaPO4 crystals that is
analogous to the STE of ScPO4 and other orthophosphates. The decay kinetics of the UV
luminescence of ScPO4 was studied over a wide temperature range from 8 to 300 K, and they
exhibited some unusual decay characteristics when subjected to pulses from an F2 excimer
laser (157 nm). These features could be ascribed to a triplet state of the STE that is split in a
zero magnetic field. A fast decay of the STE was detected as well, and therefore, we conclude
that, in addition to the slow luminescence corresponding to a transition from the triplet state,
there are singlet–singlet transitions of the STE. Time-resolved spectra of the slow and fast
decay exhibit a small shift (0.15 eV) indicating that the singlet–triplet splitting is small and
the corresponding wavefunction of the STE is widely distributed over the atoms of the ScPO4
crystal where the STE is created.

Journal of Physics: Condensed Matter 25 (2013) 385502 (6pp)

doi:10.1088/0953-8984/25/38/385502

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Cathodoluminescence of oxyfluoride glass-ceramics

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U. Rogulis, E. Elsts , J. Jansons , A. Sarakovskis , G. Doke , A. Stunda , K. Smits

Tb, Ce, Eu activated oxyfluoride glass-ceramics with the composition SiO2 $ Al2O3 $ Li2O $ LaF3 have been
studied by cathodoluminescence (CL). We compared CL intensities and decay times of the Tb, Ce, Eu
activated glass-ceramic samples and observed that the Tb activated sample has the most intense
luminescence, but the Ce activated sample has the shortest decay times. Induced optical absorption and
thermostimulated luminescence have been observed after X-ray irradiation of samples.

Radiation Measurements xxx (2013) 1-4

DOI: 10.1016/j.radmeas.2012.12.020

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