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Phosphor Ca2La6.8Eu1.2(SiO4)6O2−δ is obtained via coprecipitation and the nitrate-citrate pyrolysis method. The structure and phase composition of the synthesized apatite silicates are studied using XRD. The luminescence spectra of the sample are registered before and after pressing at pressures above 5 GPa. The magnetic properties are analyzed by means of ESR spectroscopy and vibration magnetometry. The concentrations of Eu2+ ions and constants (λ) of optical splitting between 7FJ levels in the initial sample, and in the sample after hot pressing, are calculated.

Investigation of magnetic susceptibility and electron paramagnetic resonance of the samples from the region of solid solution Zn2–2xMn2xSiO4 shows that at x ≤ 0.1 the oxidation state of all manganese ions is +2. At x ≥ 0.2, manganese is present as Mn2+ and Mn3+. Crystal-chemical studies show that defect formation mechanism changes for 0.1 ≤ x ≤ 0.2. Oxidation of part of Mn2+ ions at x > 0.1 causes luminescence concentration quenching in this region of x.

Lithium vanadium-borate glasses with the composition of 0.3Li2O–(0.7-x)B2O3–xV2O5 (x = 0.3, 0.325, 0.35, 0.375, 0.4, 0.425, 0.45, and 0.475) were prepared by melt-quenching method. According to differential scanning calorimetry data, vanadium oxide acts as both glass former and glass modifier, since the thermal stability of glasses decreases with an increase in V2O5 concentration. Fourier transform infrared spectroscopy data show that the vibrations of [VO4] structural units occur at V2O5 concentration of 45 mol%. It is established that the concentration of V4+ ions increases exponentially with the growth of vanadium oxide concentration. Direct and alternative current measurements are carried out to estimate the contribution both electronic and ionic conductivities to the value of total conductivity. It is shown that the electronic conductivity is predominant in the total one. The glass having the composition of 0.3Li2O-0.275B2O3-0.475V2O5 shows the highest electrical conductivity that has the value of 7.4 × 10−5 S cm−1 at room temperature.

The double perovskites Sr2-xCaxMgMoO6–δ with x = 0, 0.25, and 0.5 were obtained by combustion of organometallic precursors and were shown to have a tetragonal structure with the crystalline lattice parameters a = b = 5.569, c = 7.923, 7.899, 7.885 A, respectively. Calcium doping was found to improve the conductivity and decrease the activation energy values. At x = 0.5, the temperature dependence of the total conductivity has a metallic-like behavior under reducing conditions. The electrical conductivity for Sr1.5Ca0.5MgMoO6−δ was about 25 and 30 S/cm at 800 and 500 °C, respectively. Besides, the enhancement of the calcium content lead to the reduction in the area specific resistance of the Sr2−x Ca x MgMoO6−δ anode. In conjunction with the electron paramagnetic resonance study, the experimental data on the electrical conductivity demonstrated that calcium doping is accompanied by an enhanced electron component under reducing conditions. The magnetic susceptibility revealed the coexistence of itinerant electrons and paramagnetic centers in calcium-rich molybdate Sr1.5Ca0.5MgMoO6−δ.

Single-phase luminophor Zn2SiO4:V with willemite structure is prepared by hydrothermal method. It is found that the Zn: Si: V ratio between cations is 2: 0.9: 0.1. It is shown that the inclusion of vanadium in the willemite structure reduces the width of the bandgap by ΔE g ≈ 2 eV. Using a combination of spectroscopic and voltammetric techniques, it is found the zinc silicate matrix contains vanadium ions with charge states V5+, V4+, and V3+. In addition, magnetic ions form clusters.

Single-phase polycrystalline samples of Zn0.95Fe0.05O having the wurtzite structure and different morphology of particles were obtained using precursor technologies. It was found by electron spin resonance that iron enters the ZnO crystal lattice in the Fe3+ charge state. Magnetic studies revealed that the obtained samples show weak ferromagnetic properties at 300 K. A correlation between the number of oxygen vacancies and the degree of ferromagnetic ordering was found.

The photoluminescence properties of nanodimensional γ-Al2O3 produced by the thermolysis of aluminum hydroxoformate Al(OH)(HCOO)2 under different conditions have been studied. In the EPR spectrum of γ-Al2O3 prepared by thermohydrolysis, a low-field signal was detected, whose shape depends on the amount of sample. The data were interpreted assuming the existence of paramagnetic centers having no inversion center.

A morphology-controlled facile synthesis of titanium-glycolate precursors with subsequent annealing in He and air atmospheres has been exploited for the production of nanostructured composite globules, whiskers and plates of C-modified titanium dioxide. Characterisation tests proved the as-obtained globule composites to exclusively exhibit high-specific surface area (up to 150–170 m2 g−1), thus being useful for photocatalytic applications in the visible-light region. The combination of the electron paramagnetic resonance, X-ray photoelectron spectroscopy, absorption spectroscopy and transmission electron microscopy revealed the presence of three kinds of carbon in the globules: a small bandgap (with measured width of 0.8 eV) amorphous carbon surrounding the anatase nanocrystallites, C-containing radicals including carbonates on the surface of TiO2 and interstitial carbon in the oxygen position of the TiO2 lattice. It was found that the maximum visible-light photocatalytic activity of the globules is determined by the optimal surface concentration of amorphous carbon of about 0.002 wt.% m−2. Under these conditions, the highest synergic photosensitising effect on TiO2 nanocrystallites of all three kinds of carbon is expected.

This paper was devoted to explanation of the phase transitions nature in Ca12Al14O33±δ which were studied by a combination of methods: simultaneous thermal analysis, high-temperature X-ray diffraction analysis, Raman spectroscopy. One of the phase transitions is assumed to be connected with peroxide ions appearance/disappearance in mayenite at 922 K. The peroxide ions appearance reduces the system’s energy. Peroxide ions are responsible for the interaction of mayenite with water giving hydroxyl ions. Another phase transition at 1268 K is caused by changing in stability of electronic defects in mayenite. This paper enlightens correlations between the electronic defects state, the peroxide ions existence and chemical properties of Ca12Al14O33±δ .

New germanate ALa9(GeO4)6O2 (A = Li, Na, K, Rb, Cs) oxyapatites, showing promise as host lattices for phosphors with emission in the visible and infrared spectral ranges, have been obtained for the first time by ultrasonic spray pyrolysis. The discussion is focused on native defectiveness and optical properties of these compounds, depending on the nature of alkaline ions. Spray pyrolysis method was consciously used to obtain the compounds with intrinsic defects as confirmed by electron paramagnetic resonance. Reviewing available EPR data, the registered EPR response was assigned to the paramagnetic centers related to germanium tetrahedra embracing the oxygen vacancies. According to quantum-chemical calculations the oxygen-deficient centers in ALa9(GeO4)6O2 are presumably stabilized by antisite defects in the cation sublattice. Diffuse reflectance and pulse cathodoluminescence spectra of the compounds were investigated in detail, establishing a distinct dependence of optical properties on the type of alkaline ion. The observed optical absorption maxima at 275 and 370 nm were attributed to the F-like centers. The inverse dependence of luminescence intensity on the degree of defectiveness was interpreted on the assumption that these centers were involved in non-radiative energy relaxation.

In this work, solid solutions with a general formula Ca2La8(1−x)Eu8xGe6O26 were described and their excitation (PLE), emission (PL) and EPR spectra have been recorded. The morphology and elemental composition of the samples were studied by scanning electronic microscopy (SEM) and energy dispersive X-ray analysis (EDX) methods. Quantum yield, Judd–Ofelt intensity parameters, luminescence branching ratio, and oscillator strengths for magnetic dipole 5D0→7F1 and electric dipole 5D0→7F2 and 5D0→7F4 transitions are calculated for the solid solution having the largest integral intensity of emission.

Nanodisperse solid solutions Zn1−xVxO (0 ≤ x ≤ 0.03) with high numbers of defects in an oxygen sublattice are synthesized via the precursor technique. ESR analysis reveals that VO+ oxygen vacancies are the main defects of the oxygen sublattice in the Zn1−xVxO structure. The Zn1−xVxO (0 < x ≤ 0.15) solid solutions exhibit high photocatalytic activity during hydroquinone oxidation in water upon irradiation with UV and visible light.

Nanostructured ZnO powders with particles of tubular form were synthesized by a precursor method. A narrow symmetrical line with a g factor of 2.002 was detected in the ESR spectra of the materials. On the basis of analysis of the dependence of the line intensities on the heat treatment conditions it was concluded that the signal belongs to singly charged oxygen vacancies V O + .

It was established with the use of electron and ESR spectroscopic methods that in the presence of sodium sulfate, the extraction of vanadium (IV) with di-2-ethylhexylphosphoric acid takes place by a cation-exchange mechanism giving rise to two complex compounds of vanadium (IV) oxocation with sulfuric and di-2-ethylhexylphosphoric acid anions. The vanadium (IV) oxocation sulfate complex extracted in the solid state was examined with X-ray structural analysis. It was shown that the vanadium (IV) oxocation sulfate complex trihydrate crystallizes in the centrosymmetrical space group to form dimers with bridging sulfate groups.

A modified Pechini method followed by conventional and microwave heating was used to synthesise the new promising Ln2MGe4O12 (Ln = Y, Eu; M = Ca, Zn, Mn) optical hosts. Comparison between solid-state and Pechini synthesis methods showed that the latter reduces the temperature required for cyclo-tetragermanate formation. The highest yield of cyclo-tetragermanates for both methods is observed at 1,000–1,100 °C, with significantly shorter time of annealing in the case of the Pechini synthesis. Compositional, structural and morphological characterisations of the samples obtained by both routes were carried out using X-Ray powder diffraction, thermogravimetry, electron spin resonance spectroscopy, energy-dispersive X-Ray spectroscopy and scanning electron microscopy.

The magnetic interactions in the quasi-one-dimensional complex oxides Ba6NiMn4O15, Ba6Ni2Mn3O15, and Ba6Ni3Mn2O15 have been investigated using electron paramagnetic resonance and magnetic susceptibility measurements. It has been revealed that, for the Ba6Ni2Mn3O15 and Ba6Ni3Mn2O15 compounds, the magnetic moments are considerably smaller than the theoretical values and depend on the temperature. The results obtained have been interpreted under the assumption that the structure contains Ni3+ ions in which the energy level structure can lead to the above anomalies.

The results of magnetic behavior study of nickel ions, which were introduced into Zn2Fe(CN)6∙5.5H2O with channel structure, are presented. It was shown that nickel cations replace a part of Zn2+ ions or locate in the channels of lattice via the molecular mechanism sorption. It is shown that the magnetic moments μNi of the sorption products strongly depend on the content of Ni2+ ions. The values of μNi of the samples with Ni/Fe(CN)6=2.26 and 2.86 are great ~ 3.9 and 4.4 μB respectively and close to the value typical of free Ni2+ ions μ =4.47μB.

The crystal structure of the promising optical materials Ln{sub 2}M{sup 2+}Ge{sub 4}O{sub 12}, where Ln=rare-earth element or Y; M=Ca, Mn, Zn and their solid solutions has been studied in detail. The tendency of rare-earth elements to occupy six- or eight-coordinated sites upon iso- and heterovalent substitution has been studied for the Y{sub 2-x}Er{sub x}CaGe{sub 4}O{sub 12} (x=0-2), Y{sub 2-2x}Ce{sub x}Ca{sub 1+x}Ge{sub 4}O{sub 12} (x=0-1), Y{sub 2}Ca{sub 1-x}Mn{sub x}Ge{sub 4}O{sub 12} (x=0-1) and Y{sub 2-x}Pr{sub x}MnGe{sub 4}O{sub 12} (x=0-0.5) solid solutions. A complex heterovalent state of Eu and Mn in Eu{sub 2}MnGe{sub 4}O{sub 12} has been found. - Graphical abstract: Crystal structure of Ln{sub 2}MGe{sub 4}O{sub 12}, where Ln=rare-earth element or Y; M=Ca, Mn, Zn.

The transport properties of Sr5.66 Cu0.14Nb2.20 O11.30 double perovskite, which enters the homogeneity region of (Sr1-y Cu y )6–2x Nb2+2x O11+3x solid solution, are concerned. The total conductivity is differentiated into terms over wide ranges of temperatures and oxygen partial pressures $$ p_{O_2 } $$ in dry and humid atmospheres. When $$ p_{O_2 } $$ is low or high, a test sample has dominant electron transport of n- or p-type, respectively. In air ( $$ p_{O_2 } $$ = 0.21 atm), the p-type electron conductivity term increases with temperature elevation. In a humid atmosphere ( $$ p_{H_2 O} $$ = 0.02 atm), a sample is capable of a reversible incorporation of water occlusion from the gas phase; as a result, some proton conductivity term appears and ion transference numbers increase over a wide range of $$ p_{O_2 } $$ values.

A new oxide phase La1.5Sr1.5 Mn1.25Ni0.75O6.67 ± 0.05, a member of the An + 1 BnO3n+1(n=2) Rad-dlesden—Popper homologue series, was synthesized, and its structure and magnetic properties characterized. Magnetic anomalies associated with the competition between antiferromagnetic and ferromagnetic orders are observed in the range of the temperatures studied (2-400 K). The ESR spectra of the compound feature the constriction of a magnetic signal and a shift toward g(Mn4+).

Exchange interactions in the quasi-one-dimensional complex oxides Sr4MgMn2O9, Ba6MgMn4O15, Ba8MgMn6O21, and Ba9 M 2Mn5O21 (M-Cu, Zn, Mg) have been studied by electron paramagnetic resonance. The temperature dependence of the spectral parameters showed that the exchange interaction is antiferromagnetic and occurs mainly inside the manganese-containing groups and to a lesser extent between them.

New compounds Pr1.5Sr1.5CuMnO6.5 and Nd1.5Sr1.5CuMnO6.5 with an An + 1BnO3n + 1 (n = 2) structure have been synthesized. The magnetic susceptibility of both compounds follows the Curie-Weiss law above 300 K. Bellow this temperature, ESR detects the local ferromagnetic ordering of magnetic ion pairs.

PMR spectra have been recorded and the proton spin–lattice relaxation time has been measured for cubic hydride δ-ZrH2. It is found that above 290 K thermally activated diffusion of hydrogen takes place. In the region 230 K, a reversible phase transition takes place, which is due to a change in the state of hydrogen in the crystal lattice of zirconium dihydride. Possible mechanisms of this transition are discussed.

The defective structure of aluminum oxide nanopowders and ceramics based on these powders is analyzed using the electron paramagnetic resonance method. Inherent structural point defects, which are oxygen vacancies having a trapped electron (F+ centers), are identified in the nanopowders. Among the impurity defects, the signals of Fe3+, Cr3+, and Ti3+, which occupy different crystallographic positions in Al2O3 or exist as separate phases, are identified in the nanopowders and ceramics.

The effect of the preparation procedure on the defect structure of LiVO3 and Li1-xCo0.5xVO3 (0

The subsolidus phase relations in the MVO4-Ta2O5-Nb2O5 (M = Y, La) systems were studied. MNb2-2xTa2xVO9 (I) and MTa2-2xNb2xVO9 (II) solid solutions were prepared and characterized by x-ray diffraction, vibrational spectroscopy, and electron spin resonance. The range of solid solutions in I isx = 0–0.58 for M = Y and 0–0.4 for M = La; in II,x = 0–0.09 for M = Y and 0–0.1 for M = La. All of the solid solutions were found to contain V(IV) centers whose nearest neighbor environment depended on composition. The structure of LaTa2-2xNb2xVO9 was shown to contain fragments characteristic of LaNb2VO9. The lattice parameters of these solid solutions correlate with the V(IV) content.

Point defects and possible reasons for defect formation in beryllium ceramics with B3+, Al3+, Zn2+, Li+, and rare-earth element impurities produced by slip casting, dry-press molding, and high-temperature compression are investigated using electron paramagnetic resonance. A certain number of impurity centers are identified which determine the optical, luminescent, diffusion, and other physicochemical properties of beryllium ceramics.

We have developed a procedure for thermally stimulated synthesis of a cesium strontium metavanadate, Cs 2Sr(VO 3) 4:Mn 2+ (0.01, 0.50, 1.00, 5.00 at % Mn 2+), using MnO-containing starting mixtures. The EPR spectrum of the material containing 0.01 at % Mn 2+ shows a hyperfine structure due to the incorporation of a small amount of manganese into the diamagnetic double metavanadate host. The luminescent and optical properties of Cs 2Sr(VO 3) 4:Mn 2+ depend on manganese content. In contrast to higher doping levels, doping with 0.01 at % Mn 2+ increases the integrated emission intensity of the vanadate by 10% and improves its chromaticity characteristics (approaching them to those of white light). We assume that this is due to the reduction in the density of vacancy-type growth defects, such as oxygen vacancies. © Pleiades Publishing, Ltd., 2012.

Magnetic susceptibility, -ray diffraction, and electron-spin resonance studies were carried out for the calcium-doped lithium-sodium cobaltite Li 0.42Na 0.36Ca zCoO 2 (z = 0.02; 0.04). The evolution of the cell parameters with increasing calcium content in Li 0.42Na 0.36Ca zCoO 2 was considered. Phases with different calcium concentrations were found to exhibit a large diversity of susceptibilities. Spin dimer analysis was performed to explain the anomalous magnetic behavior of the calcium-rich phase. © 2012 Elsevier B.V. All rights reserved.

The state of hydrogen in tetragonal e-ZrH2.3 was probed by 1H nuclear magnetic resonance spectroscopy. Both the resonance width and Knight shift were found to exhibit anomalies around 380 K, which were interpreted as evidence for a structural phase transition involving hydrogen ordering.

Compounds with the olivine-type structures are considered as perspective materials for lithium-ion power sources for both industrial and transport applications. Lithium iron phosphate is most highly developed from this family, but LiMnPO4 is supposed as much promising, due to its higher EMF vs. lithium. One of the main lacks of this class of materials is the low electronic conductivity. The traditional ways of conductivity increase by partial replacement of Mn with other transition metal for LiMnPO4 do not result to essential success. Our approach consisting in the influence onto anion sublattice results to better effect. Such solid solutions should be suitable for oxygen nonstoichiometry creation in virtue of ability of vanadium ion for oxidation degree downturn. Using magnetic methods, we succeeded to show that the required solid solutions are really formed. The optimal synthesis conditions of LiMnP1-xVxO4-δ solid solutions were determined. It was shown, that the doping of LiMnPO4 by vanadium jointly with oxygen nonstoichiometry brings to substantial enhance of electronic conductivity in this material. Observed peculiarities of the magnetic properties indicate the restructuring in the local environment in anion sublattice.

The title compounds are promising optical materials, in which different lanthanoid elements are introduced as a sensitizer or activator.