Andris Antuzevics

University of Latvia | LU · Institute of Solid State Physics

Optical thermometers are advantageous for temperature measurement in electromagnetic fields and aggressive environments; however, their composition mostly relies on materials doped with expensive and resource-limited rare earth ions. In this article, we describe the application of calcium aluminate doped with transition metal ions (Mn ²⁺ and Cr3+)...

Advanced ceramic breeder (ACB) pebbles consisting of lithium orthosilicate (Li4SiO4) and the strengthening phase lithium metatitanate (Li2TiO3) are accepted as the European Union’s reference solid-state material for tritium breeding in thermonuclear fusion reactors. Previously, the influence of various radiation types on Li4SiO4-based ceramic breed...

Garnet-based materials are widely investigated for applications in optics. In this research, we report the structure and spectroscopic properties of novel Mg3Lu2Ge3O12: Pr3+ garnet that exhibits orange persistent luminescence. The atomic positions of Mg3Lu2Ge3O12 were calculated using Rietveld refinement. The local structure analysis using extended...

Currently, extensive research activities are devoted to developing persistent phosphors which extend beyond the visible range. In some emerging applications, long-lasting emission of high-energy photons is required; however, suitable materials for the shortwave ultraviolet (UV–C) band are extremely limited. This study reports a novel Sr2MgSi2O7 pho...

It is fundamentally important to understand, control, and predict the effect of irradiation on the structure and optical properties of functional materials. In this work, the thermal stability of fast-neutron induced point defects has been investigated in polycrystalline transparent alumina ceramics. The results of a combined study of electron para...

The optical spectra of a single crystal of α-Al2O3Cr³⁺ were studied in a wide temperature range. The crystal was demonstrated to have a potential for optical thermometric applications. Three ways of measuring temperature were tested and analyzed: i) luminescence intensity ratio of the R1 and R2 lines; ii) change of the full width of half maxima of...

Low-temperature ultraviolet-excited photoluminescence (PL) and recombination luminescence (RL) properties of La-doped Ca2SnO4 have been investigated by luminescence, electron paramagnetic resonance (EPR) and optically-detected magnetic resonance (ODMR) techniques. Two PL and RL bands at 340 nm and 450 nm have been observed. PL excitation spectra me...

In this work novel garnet persistent luminescence phosphor Mg3Y2Ge3O12: Tb³⁺ (MYG: Tb³⁺) with bright blue to green tuneable emission is reported. MYG: Tb³⁺ samples with Tb³⁺ content ranging from 0 to 100% were analysed. X-ray absorption spectroscopy analysis showed that Tb³⁺ ions incorporate in the garnet structure by replacing Y³⁺ ions. Optimal do...

In this study, we report broadband near-infrared persistent luminescence of a novel MgGeO3: Cr³⁺ material. The luminescence can be excited by the ultraviolet radiation and detected for more than 16 hours. Optical and electron paramagnetic resonance spectroscopy experiments suggest that the observed bands appear as a result of interaction between Cr...

In the present work, three different Mn²⁺-doped calcium pyrophosphate (CPP, Ca2P2O7) polymorphs were synthesized by wet co-precipitation method followed by annealing at different temperatures. The crystal structure and purity were studied by powder X-ray diffraction (XRD), Fourier-transform infrared (FTIR), solid-state nuclear magnetic resonance (S...

Manganese doped polycrystalline CaAl4O7 samples with doping concentrations in 0.1–2.0 mol% range were synthesized using the solid-state synthesis method. Photoluminescence (PL) and electron paramagnetic resonance (EPR) spectroscopy techniques were applied to characterize the local structure and properties of Mn ions in CaAl4O7. With excitation of 4...

Proton exchange membranes (PEM), which have been commonly used in fuel cells have raised interest for the application in harsh environments involving ionizing radiation. Therefore, radiation stability and ability to sustain their functionality under the radiation environment are of great interest. Within this study, electron beam irradiation in dos...

Lithium orthosilicate (Li4SiO4) containing ceramics are currently being developed as potential solid-state candidate materials for tritium breeding in future thermonuclear fusion reactors. Under the expected operational conditions, the tritium breeding material will be exposed to the simultaneous influence of several strong energetic factors, for e...

The origin of bright cyan persistent luminescence in La³⁺-doped Ca2SnO4 is investigated by optical and electron paramagnetic resonance spectroscopy methods. The incorporation of La³⁺ ions in the material stimulates the formation of Sn²⁺ emission centers and charge trap centers. After exposure of the material to UV radiation, charge transfer process...

The natural spinel crystal MgAl2O4 containing the Cr³⁺ ions was studied experimentally and theoretically in this paper. The absorption and emission spectra at room and low temperatures were recorded. The experimental spectroscopic results were aided with the crystal field calculations, which returned the energy level schemes of the Cr³⁺ ions at the...

An electron spin resonance (ESR) and photoluminescence signal is observed in the as grown single crystal of stishovite indicating the presence of defects in the non-irradiated sample. Photoluminescence of the as received stishovite single crystals exhibits two main bands - a blue at 3 eV and an UV at 4.75 eV. Luminescence is excited in the range of...

This article presents the results of a study of radiation-induced defects in various synthetic calcium phosphate (CP) powder materials (hydroxyapatite—HA and octacalcium phosphate—OCP) by electron paramagnetic resonance (EPR) spectroscopy at the X, Q, and W-bands (9, 34, 95 GHz for the microwave frequencies, respectively). Currently, CP materials a...

LaOCl doped with 0–10 mol% Cr was synthesized by thermal decomposition of chlorides. X-ray diffraction (XRD) analysis revealed that incorporation of chromium results in a decrease of the lattice parameter a and a simultaneous increase of the lattice parameter c. The local structure of chromium ions was studied with X-ray photoelectron (XPS), X-ray...

Photoluminescence, photochromism and defect formation were analysed in Ca2SnO4 doped with 0–20% Al³⁺. Bright cyan luminescence attributed to Sn²⁺ was detected in all samples. Introduction of Al³⁺ in Ca2SnO4 led to an enhancement of Sn²⁺ emission by up to 70% in comparison with an undoped sample. After exposure to UV irradiation, two absorbance band...

Reddish-orange persistent luminescent Ca2SnO4: 0.1% Sm³⁺ co-doped with 0–10% Gd³⁺ was prepared using solid state synthesis. The phase formation and morphology was analyzed using X-ray diffraction and scanning electron microscopy. Incorporation of Sm³⁺ and Gd³⁺ in Ca2SnO4 lattice was investigated using site-selective spectroscopy and electron parama...

Octacalcium phosphate (OCP) (Ca8H2(PO4)6*H2O] has attracted increasing attention over the last decade as a transient intermediate to the biogenic apatite for bone engineering and in studies involving the processes of pathological calcification. In this work, OCP powders obtained by hydrolysis of dicalcium phosphate dehydrate were subjected to X-and...

In this study, yttrium aluminium garnet (YAG) specimens in which yttrium was partially substituted by lanthanum Y3-xLaxAl5O12 (YLaAG) were prepared by an aqueous sol-gel method. YLaAG samples were analyzed by X-ray diffraction (XRD), solid state nuclear magnetic resonance (NMR) and electron paramagnetic resonance (EPR) methods. The presence of Ce³⁺...

Materials with long persistent luminescence (PersL) have caused widespread interest among scientists and industry for decades. Currently, there is widely available information on the long persistent luminescence materials with emission in the blue and green spectral range, while the number of publications on the afterglow in the red and near-infrar...

The present study investigates thermally induced crystallization and phase evolution of amorphous calcium phosphate (ACP) partially substituted with Fe3+ ions (M/P = 1.5 : 1). It was demonstrated that the...

Original results on the EPR and photoluminescence Cr 3+ ions in natural magnesium aluminum spinel (MgAl 2 O 4) are presented. The photoluminescence spectra of Cr 3+ ions in natural MgAl 2 O 4 have been measured before and after irradiated by fast neutrons.

Electron paramagnetic resonance (EPR) is a well-established spectroscopic technique for electronic structure characterization of rare-earth ion impurities in crystalline and amorphous hosts. EPR spectra of erbium-doped glass matrices and nanocomposites can provide information about local structure variations induced by changes in chemical compositi...

Original results on the EPR and photoluminescence Cr3+ ions in natural magnesium aluminum spinel (MgAl2O4) are presented. The photoluminescence spectra of Cr3+ ions in natural MgAl2O4 have been measured before and after irradiated by fast neutrons.

In this paper, we have performed comparative analysis of EPR, optical absorption (OA) and luminescence spectra for a series of Gd3Ga5O12 (GGG) single crystals irradiated with fast neutrons with fluencies varied from 10¹⁶ to 10²⁰n/cm². In a crystal irradiated with the maximum neutron fluence, the EPR spectra demonstrated the formation of several par...

In this work, a series of Mn²⁺-doped α-tricalcium phosphate (α-TCP) powders was synthesized by wet co-precipitation method followed by high-temperature annealing and thermal quenching. It was shown that Mn²⁺-doped α-TCP polymorph can be successfully synthesized with a doping level up to 1 mol%. All Mn-doped samples exhibited a broadband emission in...

In the present work, Fe³⁺ and Zn²⁺ co-substituted β-tricalcium phosphate (β-TCP) has been synthesized by wet co-precipitation method. Co-substitution level in the range from 1 to 5 mol% has been studied. Thermal decomposition of as-prepared precipitates was shown to be affected by introducing of foreign ions, decreasing the decomposition temperatur...

Recombination luminescence (RL) and RL-detected electron paramagnetic resonance (RL-EPR) in BaY2F8 single crystal has been investigated after irradiation with X-rays at low temperature. The recombination process, which lasts for several hours at 4 K, results in several broad bands in the RL spectrum. RL-EPR spectra show pronounced angular dependenc...

Assessment of activator distribution in lanthanide doped nanocomposites is an important and challenging task. Oxyfluoride glass ceramics have been chosen as a model system to characterize incorporation efficiency of Eu³⁺ ions in CaF2 nanocrystals using a combination of X-ray diffraction (XRD) and electron paramagnetic resonance (EPR) techniques. La...

Black colour TiO2 films were synthesized on amorphous fused silica substrates by DC magnetron sputtering technique with carbon powders placed at the working magnetron surface. Comprehensive sample analysis by X-ray diffraction, energy dispersive X-ray spectroscopy and X-ray photoelectron spectroscopy showed that the rutile/anatase heterostructure T...

Effect of Mn doping on the low-temperature synthesis of tricalcium phosphate (TCP) polymorphs was demonstrated in α- and β-TCP polymorphs prepared by wet precipitation method under identical conditions and annealed at 700 °C. Calcium phosphates with Mn doping level in the range from 1 to 5 mol% were studied and the formation of desired polymorph wa...

An electron spin resonance (ESR) and photoluminescence signal is observed in the as grown single crystal of stishovite indicating the presence of defects in the non‐irradiated sample. The photoluminescence of the as received stishovite single crystals exhibits two main bands – a blue at 3 eV and an UV at 4.75 eV. Luminescence is excited in the rang...

Gadolinium doped SrF2 nanoparticles have been synthesized by the precipitation method and characterized by site-selective optical spectroscopy and electron paramagnetic resonance (EPR) spectroscopy methods at cryogenic temperatures. The type of Gd³⁺ centres present in SrF2 is strongly dependent on the heat treatment parameters – the chosen temperat...

The advances of EPR spectroscopy for the detection of activators as well as determining their local structure in the crystalline phase of glass ceramics is considered. The feasibility of d-element (Mn2+, Cu2+) and f-element (Gd3+, Eu2+) ion probes for the investigation of glass ceramics is discussed. In the case of Mn2+, the information is obtained...

Electron paramagnetic resonance (EPR), magnetic circular dichroism (MCD) and EPR detected via MCD (MCD-EPR) investigations have been performed on rare-earth activated oxyfluoride glasses and glass-ceramics. Er³⁺, Gd³⁺, and Mn²⁺ activators in oxyfluoride glass-ceramics show paramagnetic MCD behaviour and the MCD-EPR has been detected. The results of...

Different compositions of europium doped aluminosilicate oxyfluoride glass ceramics prepared in air atmosphere have been studied by electron paramagnetic resonance (EPR) and optical spectroscopy methods. X-ray diffraction (XRD) and transmission electron microscopy (TEM) measurements show presence of homogenously distributed SrF2 nanocrystals after...

A fiber preform with P-doped silica core is studied by luminescence methods. P-doped silica was synthesized via the SPCVD method on a substrate tube made of pure silica glass F300. Two luminescence bands were detected under excitation of the F2 excimer laser (157 nm). One band is in UV range at 4.6 eV (265 nm) with two time constants ~ 30 ns and 5...

Gd3 + doped aluminosilicate oxyfluoride glasses and glass-ceramics containing SrF2 and BaF2 crystallites have been studied by differential thermal analysis (DTA), X-ray diffraction (XRD), transmission electron microscopy (TEM), photoluminescence (PL) and electron paramagnetic resonance (EPR) spectroscopy techniques. A pronounced EPR fine structure...

Gadolinium doped scintillators could be efficient neutron detectors with a minimal residual radioactivity and good temperature stability [1]. In this research we analyze localization and properties of Gd ³⁺ dopants in oxyfluoride glass-ceramics containing NaLaF 4 nanocrystals and in polycrystalline NaLaF 4 powders. Glass samples with the compositio...

Magnetic resonance investigations of the Gd3 + centre structure in the oxyfluoride glass and glass-ceramics (GCs) have been carried out. The electron paramagnetic resonance (EPR) measurements showed the presence of low symmetry Gd3 + centres in the glass sample. The cubic Gd3 + centre appeared in the glass-ceramics after heat treatment of the sampl...

Zero field splitting (ZFS) of Gd3+ impurity in ScF3 is studied by electron paramagnetic resonance (EPR) at 77 and 295 K. ZFS parameter b4 values obtained from angular dependence simulations show that regardless of negative thermal expansion (NTE) in ScF3 temperature dependence of |b4| is similar to other cubic fluoroperovskites. Our analysis of ZFS...

Electron paramagnetic resonance (EPR) measurements have been made for two perpendicular planes in a LiYF4 crystal before and after x-ray irradiation at room temperature. Analysis of the EPR spectrum angular dependence shows the presence of two defects - an impurity ion, which was embedded during the crystal growth process, and an x-ray induced defe...