A.N.Trukhin , K.Smits , J.Jansons , D.Berzins , G.Chikvaidze , D.L.Griscom
Luminescence of phosphorus doped crystalline α-quartz and phosphosilicate glass with content
3P2O5 7SiO2 was studied.Water and OH groups are found by IR spectra in these materials.The spectrum of lumines cence contains many bands in the range 1.5–5.5 eV. The luminescence bands in UV range at 4.5–5 eV are similar in those materials. Decay duration in exponential approximation manifests a time constant about 37 ns. Also a component in ms range was detected. PL band of ms component is shifted to low energy withrespect to that of 37 ns component. This shift is about 0.6 eV. It is explained as singlet–triplet splitting of excited state. Below 14 K increase of luminescence kinetics duration in ms range was observed and it was ascribed to zero magnetic field splitting of triplet excited state of the center.
Yellow–red luminescence was induced by irradiation in phosphorus doped crystalline α-quartz,
phosphosilicate glasses.The yellow luminescence contains two bands a t600 and 740 nm. Their decay is similar under 193 nm laser and maybe fitted with the first order fractal kinetics or stretched exponent.
Thermally stimulated luminescence contains only band at 600 nm. The 248 nm laser excites luminescence at 740 nm according to intracenter process with decay time constant about 4ms at 9 K.
Both type of luminescence UV and yellow were ascribed to different defects containing phosphorus.
P-doped α-quartz sample heated a t550 °C become opalescent. IR spectra related to water and OH
groups are changed. Photoluminescence intensity of all three bands,UV (250nm), yellow (600nm) and
red (740nm) strongly diminished and disappeared after heating to 660 °C. Radiation induced red
luminescence of non-bridging oxygen luminescence center (NBO) appeared in crystal after heat treatment. We had observed a crystalline version of this center (Skujaetal., Nuclear Instruments and Methods in Physics Research Section B Beam Interactions with Materials and Atoms. 2012; 286: pp.159–168).
Effect of heat treatment explained as sedimentation of phosphorus in some state. Keeping of treated
sample at 450–500 °C leads to partial revival of ability to create yellow luminescence center under irradiation.
Journal of Luminescence 166(2015)346–355
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
L. Grigorjeva , D. Millers , K. Smits , A. Sarakovskis , W. Lojkowski , A. Swiderska-Sroda , W. Strek ,
Transparent Ce and Ce/Pr doped YAG ceramics were prepared under high pressures (up to 8 GPa) and relative
low temperature (450 C). Grain size of the ceramics is less than 50 nm. However unknown defects
or disorders strains on grain boundaries caused the additional absorption in these ceramics. The luminescence
intensity, spectra and the decay time dependence on pressure applied during ceramic preparation
were studied. Concentration of some intrinsic point defect was reduced under the high pressure applied
for sintering process.
It is shown that formation time of the excited state of Ce luminescence depends on the pressure applied
during ceramic sintering.
Optical Materials 34 (2012) 986–989
L. Grigorjeva , D.Millers , K.Smits , J.Grabis , J.Fidelus , W. qojkowski , T.Chudoba , K.Bienkowski
The luminescence properties of ZnO ceramics with grains 100-5000 nm sintered by different techniques from nanopowders were studied. The luminescence decay times were compared with that obtained for ZnO singlecrystal. The temperature dependence of non-exponential decay of defect luminescence (2.0-2.6 eV) was measured in wide time, intensity and temperature range.The luminescence decay kinetic at T=20 K shows the decay close to I(t) w t1 dependence. At temperature region 50-250 K the decay kinetics is more complicated since the TSL was observed in this temperature region. It is shown that the luminescence properties of NP and ceramics strongly depend on defect distribution on grains surface
and the volume/surface ratio determine the luminescence decay in ZnO nanostructures and ceramics.
L. Grigorjeva , D. Millers , K. Smits , V. Pankratov , W. Łojkowski, J. Fidelus , T. Chudoba , K. Bienkowski , C. Monty
Fast photoluminescence spectra in the spectral region of 3.1–3.45 eV in ZnO and ZnO:Al ceramics were
studied at 14 and 300 K. Ceramics with grains smaller than 100 nm were sintered from nanopowders
by high pressure (8 GPa) and low temperature (350 C). Ceramics with grain sizes 1–5 lm were sintered
at 1400 C. It is shown that excitonic luminescence spectra depend on the ceramics grain size, post preparing
annealing and doping. The excitonic luminescence decay time was faster than 2 ns and the afterglow
at 30 ns was 0.05%.
Optical Materials 2009
R. Andrew Wall, Kyle C. Lipke, K. B. Ucer, R. T. Williams, D. Millers, K. Smits, and L. Grigorjeva
We report transient absorption induced by electron-hole excitation
in undoped ZnO. A laser pump/continuum probe
method covers 2–300 ps, and an electron pulse with lamp
transmission covers 8–300 ns. The broad absorption spectrum
increases monotonically with wavelength from 900 to 1600
nm. Following a reasonable hypothesis that the free-carrierlike
induced infrared absorption is proportional to the total
number of free carriers, excitons, and shallow-trapped carriers
in the sample, these data allow setting an upper limit on
the quantum efficiency of a specified lifetime component of
luminescence. For the undoped commercial ZnO studied in
this report, the quantum efficiency of room temperature excitonic
luminescence is less than 5%. This means that there is
significant room for improvement in applications aiming to
use room-temperature excitonic blue luminescence of ZnO
for fast scintillators and light sources. Direct observation that
a large majority of excitations are tied up for more than 100
nanoseconds in shallow traps confirms the premise for studies
undertaken at Oak Ridge National Laboratory to improve the
excitonic luminescence yield and decay rate of ZnO by donor
doping. The preliminary results presented here on undoped
ZnO suggest that induced absorption measurements should be
a useful diagnostic of quantum efficiency while studying such
Physica Status Solidi (C) Current Topics in Solid State Physics
phys. stat. sol. (c) 6, No. 1, 323–326 (2009)