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This paper presents a brief review of the state-of-the-art in the field of the preparation and characterization of the most widespread types of ferrites: ferrites with the spinel structure, hexaferrites, ferrites with the garnet structure, and orthoferrites. The present review is concerned primarily with advances in the synthesis and characterization of ferrites with various structures in the past two years (2020 and 2021). We compare available data on the feasibility of replacing trivalent Fe atoms by other atoms and discuss potential applications of ferrite solid solutions. The present results make it possible to identify promising directions of the development of this area of research and the associated current problems. [ABSTRACT FROM AUTHOR]

This paper presents a comparative analysis of the magnesium dopant distribution in the melt–crystal system during Czochralski growth of LiNbO3:B:Mg lithium niobate single crystals from a melt via sequential dilution of the melt with a nominally pure LiNbO3 growth charge. In the growth process, we used granulated growth charges prepared by two procedures: using homogeneous doping of a Nb2O5:B:Mg + Li2CO3 precursor and by solid-state reaction in a Li2CO3 + Nb2O5 + H3BO3 + MgO mixture. It has been shown that, all other crystal growth conditions being the same, homogeneous doping allows more magnesium (by ~25%) to be introduced into crystals, whereas the boron concentration remains at a trace level. The optical quality of the crystals has been assessed by a high-speed method, and their piezoelectric modulus d333 has been determined. The results demonstrate that lithium niobate single crystals with high optical quality can be obtained using both doping procedures. The choice of the growth process for LiNbO3:B:Mg single crystals will depend on its cost effectiveness. [ABSTRACT FROM AUTHOR]

This paper reports a process for the growth of optically homogeneous lithium niobate single crystals containing boron as a dopant. A LiNbO3:B crystal has been grown by the Czochralski technique using a single-phase growth charge synthesized from a Nb2O5:B precursor and lithium carbonate. We have assessed the optical quality of the crystal by a high-speed method from the number of scattering centers, evaluated its single-domain state by piezoacoustic measurements, and calculated its d333 piezoelectric modulus component. The results demonstrate that the crystal has a high degree of optical uniformity and is single-domain. The proposed method for LiNbO3:B crystal growth can serve as a basis of a commercial-scale process for the preparation of doped lithium niobate single crystals for various engineering applications. [ABSTRACT FROM AUTHOR]

This paper presents a detailed experimental study of extrinsic photoelectric effects caused by combined excitation—induced extrinsic photoconductivity (IEP) and optical and thermal elimination of a photoelectric fatigue (PEF) state—in undoped and holmium- and erbium-doped (10–5 to 10–1 at %) indium selenide (n-InSe) crystals. The observed specific features of IEP and detection and elimination of a PEF state are shown to be due to not only the presence of different types of trap levels in the band gap of the crystals but also the presence of random macroscopic defects. [ABSTRACT FROM AUTHOR]

The paper reviews scientific studies on the synthesis and properties of magnetic nanocrystals based on ferrites and diluted magnetic semiconductors that have been reported mostly in the past 10–15 years. New data on controlling the characteristics of these materials by doping and practical applications are discussed. [ABSTRACT FROM AUTHOR]

This paper presents an experimental study of the effect of doping with manganese on the vapor phase growth of lead(II) iodide crystals in a closed system and their properties. The manganese concentration in the grown crystals and the mass transport rate in the PbI2–I2 system are determined by the Mn concentration in the growth charge and the temperature of the source zone. We have obtained single crystals of the following morphological types: elongated ribbons, ribbons with sharp ends, plates, and their combinations and intergrowths. Doping with manganese has been shown to influence low-temperature (T = 5 K) photoluminescence spectra of PbI2. [ABSTRACT FROM AUTHOR]

Ammonium iodide (NH4I) has been shown to have an inhibiting effect on the growth kinetics of lead sulfide films at initial NH4I concentrations in solution from 0.05 M to 0.40 M. The addition of the inhibitor leads to a decrease in grain size, an increase in the fraction of nanoparticles in the PbS films to ~13%, and an increase in the iodine content of the films to 3.7 at %, depending on growth conditions. X-ray diffraction characterization has shown that the films have a B1 cubic structure (sp. gr. ). Increasing the inhibitor concentration in solution leads to an increase in the lattice parameter of the lead sulfide from 0.59315(1) to 0.59442(3) nm, due to iodine substitution for sulfur in the PbS crystal lattice. The spectral sensitivity peak and the long-wavelength edge of the photoresponse of the PbS films shift to shorter wavelengths from 2.5 to 2.2 and from 3.0 to 2.8 μm, respectively, which is attributable to the formation of the wide-band-gap phase PbI2. Using low-temperature measurements, the thermal band gap of the films grown in the presence of 0.15 and 0.25 mol/L NH4I has been determined to be 0.46 and 0.51 eV. The respective activation energies for acceptor impurity levels are 0.135 and 0.153 eV. The iodine-doped PbS films offer a relatively high voltage responsivity in the IR spectral region owing to an n- to p-type conversion, in combination with an anomalously short response time. [ABSTRACT FROM AUTHOR]

We analyze the effect of tungsten doping of sol–gel derived polycrystalline vanadium dioxide films on the temperature dependence of their resistivity across the metal–semiconductor transition. Experimental resistivity hysteresis data demonstrate that, with increasing doping level, the phase transition temperature of the films decreases, their hysteresis loop extends over a broader temperature range, and their resistivity jump drops. We have constructed coercive temperature distribution functions and compared them with size distributions of crystalline grains in the undoped and doped films. The results lead us to conclude that tungsten doping of vanadium dioxide has no effect (at least up to 6 at % W) on structure formation in polycrystalline films. The observed changes in phase transition parameters upon doping are, most likely, caused by the increase in donor defect density and the large scatter in dopant concentration in individual grains. [ABSTRACT FROM AUTHOR]

A technologically feasible process has been proposed for the preparation of a LiNbO3:Mg,B growth charge from a Li2CO3 + Nb2O5 + MgO + H3BO3 mixture. Using such a growth charge, we have grown LiNbO3:Mg,B crystals with a highly uniform dopant distribution. High-speed evaluation of optical homogeneity has shown that the LiNbO3:Mg,B crystals have high optical quality. Using amplitude–frequency response and d333 piezoelectric modulus measurements, we have demonstrated a high degree of unipolarity of the LiNbO3:Mg,B crystals. The optical damage resistance and homogeneity of the LiNbO3:Mg,B crystals have been assessed using photoinduced light scattering and laser conoscopy. The results suggest that LiNbO3:Mg,B crystals with a weak photorefractive effect can be regarded as a new optical material for laser light conversion. [ABSTRACT FROM AUTHOR]

A technologically feasible process has been proposed for the preparation of homogeneous single-phase magnesium–boron codoped lithium niobate growth charge. It has been used in Czochralski growth of LiNbO3:Mg,B lithium niobate single crystals with a highly uniform dopant distribution. The crystals have been shown to have optical quality. The results of this study are important for designing a process for the preparation of materials with a weak photorefractive effect to be used in nonlinear optics and other areas of science and technology. [ABSTRACT FROM AUTHOR]

We demonstrate that increasing the zinc concentration in Zn-doped lithium niobate crystals to their first concentration threshold (~3.0 mol % ZnO) leads to a decrease in photovoltaic field, an increase in diffusion field, and a decrease in the luminescence intensity of NbLi emission centers. As the zinc concentration approaches the second concentration threshold (~6.8 mol % ZnO), the photovoltaic field increases, which is accompanied by a decrease in diffusion field and band gap. In addition, the integrated luminescence intensity drops as a consequence of the reduction in the concentration of defect centers in the form of NbLi–NbNb bipolaron pairs. At the same time, the emission intensity of NbLi small polarons increases and the photorefractive effect decreases markedly. [ABSTRACT FROM AUTHOR]

We have studied the catalytic activity of LiZr2(PO4)3-based NASICON-type phosphates for conversion of C2 and C3 aliphatic alcohols with the aim of selectively preparing C2–C4 olefins. Selectivity has been controlled via partial heterovalent substitutions of In3+ or Nb5+ for Zr4+ or Mo for phosphorus. We have investigated the structure and morphology of the synthesized catalysts. The nature of the dopants has been shown to play a key role in determining the selectivity of the catalysts studied. Partial In3+ substitution for Zr4+ improves the dehydrogenating properties of the materials, whereas partial substitutions of Nb5+ for Zr4+ and Mo6+ for P5+ improve their dehydrating properties. We have demonstrated the possibility of highly selective preparation of ethylene and butylenes from ethanol and of propylene from propanol-1 and propanol-2. [ABSTRACT FROM AUTHOR]

Accumulation of microcracks in response to point impact damage in MgAl2O4 ceramics doped with Cr3+ ions has been studied using acoustic emission measurements. The results demonstrate that the maximum crack length at a higher chromium concentration in the ceramics is smaller than that at lower doping levels. By contrast, doping with LiF (in addition to Cr3+) reduces the decrease in microcrack length caused by chromium oxide. [ABSTRACT FROM AUTHOR]

Nanocrystalline La1 –xCdxFeO3 (x = 0, 0.05, 0.1, 0.15, 0.2) powders with a narrow homogeneity range (xmax = 0.09 according to X-ray microanalysis and X-ray diffraction data) have been synthesized via coprecipitation followed by thermal annealing at 950°C for 1 h. The addition of Cd2+ cations leads to a decrease in average crystallite size from 10–70 nm at x = 0 to 5–60 nm at x = 0.1 (according to transmission electron microscopy data). The synthesized nanocrystals have ferrimagnetic properties. [ABSTRACT FROM AUTHOR]

A method has been demonstrated for doping carbon nanotubes (CNTs) with nitrogen during synthesis in an acetylene + ammonia atmosphere at different temperatures in the range 550–750°C, and conditions have been found for effective nitrogen doping of CNTs depending on synthesis temperature. The concentrations of various elements in the synthesized CNTs have been determined by X-ray photoelectron spectroscopy. Raman measurements with the use of a Raman microscope have made it possible to follow variations in the relative intensities of the G and D bands as functions of nitrogen dopant concentration in the CNTs. We have detected strong Raman overtone combination satellites whose parameters depend on the structural perfection of the synthesized CNTs. [ABSTRACT FROM AUTHOR]

Colloidal Cd1 –x(Ca,Sr)xS and Cd1 –xCaxS:Eu3+ (0 < x < 0.20) quantum dots (QDs) have been synthesized by an emerging reagent method in a methylmethacrylate (MMA) medium. The mole fraction of Eu3+ in the starting reaction mixtures was varied from 0 to 0.80 relative to the Ca2+ concentration. Using radical block polymerization of MMA, we have obtained transparent luminescent polymethylmethacrylate (PMMA) based composites: PMMA/Cd1 –x(Ca,Sr)xS and PMMA/Cd1 –xCaxS:Eu3+. Luminescence excitation in the composites is due to interband electron transitions in the CdS and electron transitions from the ground state to excited states of the Eu3+ ions. The observed broadband luminescence is due to structural defects in the CdS crystals, and narrow-band luminescence originates from 5D0 → 7Fj electron transitions of the Eu3+ ions in the bulk of the CdS crystals, in complexes on their surface, and in the bulk of the polymer matrix, independent of the semiconductor particles. The position and intensity of the observed spectral bands depend on the composition and concentration of the components, excitation wavelength, and other factors. [ABSTRACT FROM AUTHOR]

We have developed a method for the synthesis of a zinc-doped lithium tantalate (LiTaO3) growth charge using high-purity tantalum-containing solutions, which is based on the heat treatment of lithium-, tantalum-, and zinc-containing citrate precursors. The thermolysis products have been characterized by thermal analysis, X-ray diffraction, and infrared absorption spectroscopy. We have optimized synthesis conditions and zinc concentration for obtaining a single-phase LiTaO3〈Zn〉 growth charge. Using the proposed process, we have obtained LiTaO3〈Zn〉 materials with tailored dopant concentrations, which can be used in both LiTaO3〈Zn〉 crystal growth and the preparation of doped lithium tantalate-based functional ceramics. [ABSTRACT FROM AUTHOR]

We have studied EPR spectra of MnO2-activated fluorozirconate and fluorohafnate glasses in order to determine the oxidation state and distribution of the manganese ions. The effect of activator concentration on the ratio of the percentage of free Mn4+ ions to that of ions in clusters in the glasses has been investigated for the first time. The results demonstrate that, at high activator concentrations, the manganese ions in the glasses are clustered, and only a small fraction of them are present as isolated ions. Reducing the manganese concentration leads to an increase in the percentage of free Mn4+ ions. Devitrification is accompanied by dissociation of the clusters and a transition of the ions to an isolated state. [ABSTRACT FROM AUTHOR]

Using photoinduced light scattering parameters at wavelengths of 476.5, 488.0, 514.5, and 532.0 nm, we have assessed the photovoltaic and diffusion field strengths in nominally undoped and doped lithium niobate crystals. The results demonstrate that the photovoltaic field is strongest at an excitation wavelength of 514.5 nm. [ABSTRACT FROM AUTHOR]

We have studied the luminescence of europium(III)-doped materials based on yttria and yttrium oxyfluorides. The materials were prepared through heat treatment of fluorine-containing yttrium and europium(III) thioacetamide complexes at temperatures of 400, 600, and 800°C for 2 to 6 h. The products were shown to consist of (EuхY1 –х)F3, (EuхY1 –х)5O4F7, (EuхY1 –х)OF, and (EuхY1 –х)2O3 phases. We have proposed a scheme that reflects the formation sequence of the main components of the materials in the above temperature range. Narrow-band luminescence of the materials has been shown to arise from Eu3+5D0 → 7Fj electronic transitions. The origin of the observed broad luminescence band peaking in the range 480–500 nm can be understood in terms of surface structural defects, the particle size, and the broad particle size distribution. The luminescence spectrum has been shown to be influenced by the starting-mixture composition, synthesis conditions, host composition, and excitation wavelength. Some of the observed luminescence features have been shown to be due to the effect of S2– ions in the composition of europium-containing activator centers. [ABSTRACT FROM AUTHOR]

Abstract—: We have studied luminescence and electron paramagnetic resonance (EPR) spectra of manganese-activated fluorozirconate glasses. In ZrF4-BaF2-LaF3-AlF3-NaF (ZBLAN) glasses, manganese gives a green luminescence band peaking at 545 nm. Partial chlorine substitution for fluorine in the glass leads to a shift and broadening of the luminescence band. Complete BaCl2 substitution for BaF2 in ZBLAN〈Cl〉 fluoride chloride glass increases the peak emission wavelength to 610 nm. The observed distinctions between the EPR spectra of the Mn-doped ZBLAN and ZBLAN〈Cl〉 glasses correlate with those between their luminescence spectra. The effect of chlorine substitution for fluorine on the luminescence and EPR spectra of the fluorozirconate glass is tentatively attributed to a change in the oxidation state of the manganese ions. [ABSTRACT FROM AUTHOR]

The crystallization of amorphous Sn-doped TlInS2 films into three polymorphs has been studied by kinematic electron diffraction. The results demonstrate that the crystallization of 30-nm-thick amorphous films produced by thermal evaporation in high vacuum can be described by the Avrami-Kolmogorov equation: Vτ = V0[1-exp(-kτm)]. Kinematic electron diffraction patterns of the TlIn1-хSnxS2 films have been used to assess the effect of doping with Sn on the growth dimensionality and the activation energy for the crystallization of the amorphous films and the unit-cell parameters of the resultant crystalline materials. Doping extends the temperature range and effective activation energy for the crystallization of the amorphous films. [ABSTRACT FROM AUTHOR]

Li1 + xHf2-xInx(PO4)3 (x = 0, 0.05, 0.1) materials have been prepared by solid-state reactions and characterized by X-ray diffraction, low-temperature nitrogen adsorption measurements, and scanning electron microscopy. The materials consist of NASICON-type lithium hafnium double phosphates with a hexagonal structure. Milling in a planetary mill has been found to increase the specific surface area of the Li1 + xHf2-xInx(PO4)3 materials by almost one order of magnitude (from 1.5 to 13 m2/g in the case of LiHf2(PO4)3). The materials with a larger surface area exhibit catalytic activity for ethanol dehydration reactions and are less active for ethanol dehydrogenation. Ethanol conversion predominantly yields diethyl ether at low temperatures and ethylene at higher temperatures. The diethyl ether selectivity of the catalytic processes reaches 85% at 350°C, with 60% conversion, and the ethylene selectivity reaches 96% at 510°C, with 100% conversion. Indium doping raises the high-temperature acetaldehyde selectivity from 4 to 8% and leads to the formation of C4 hydrocarbons as reaction products. C4 selectivity reaches 15 and 17% in the case of the Li1.05Hf1.95In0.05(PO4)3 and Li1.1Hf1.9In0.1(PO4)3 materials, respectively (420°C, 97 and 92% conversion, respectively). [ABSTRACT FROM AUTHOR]

Photoinduced light scattering and optical spectroscopy have been used to study the photorefractive effect and determine the band gap in nominally undoped congruent and stoichiometric lithium niobate crystals, as well as in a series of congruent LiNbO3 crystals doped with Mg, Zn, B, Gd, Y, and Er cations and LiNbO3 single crystals codoped with Mg:Gd, Mg:Fe, Mg:Y, and Mg:Ta. [ABSTRACT FROM AUTHOR]

The influence of low concentrations (1 mol %) of co-dopants (Y, Ce, Gd, Er, La, Zn, Mn, Co and Cu) on the microhardness and fracture toughness of ZrScO (10.5ScSZ) solid electrolyte was studied by the indentation method. It was shown that co-doping of 10.5ScSZ by the rare-earth elements (Y, Ce, Gd, Er) results in microhardness increase on 4-45% due to stabilization of cubic phase in the grains, while the microhardness changing upon transition metals (Mn, Cu, Co, Zn) introduction is caused by the grain boundaries modification. The microhardness decreases on ~4 and 10% upon doping by Mn and Cu, accordingly, whereas the introduction of Co and Zn results in its increase approximately by 2 times. It was shown also that the influence of all investigated dopants on the fracture toughness is insignificant. The maximal effect observed for Cu was the fracture toughness increase from 2.1 up to 2.6 MPa m. [ABSTRACT FROM AUTHOR]

Analysis of IR absorption spectra of LiNbO:Zn (0.04-4.46 mol % ZnO) and LiNbO:Mg (0.19-5.91 mol % MgO) single crystals in the stretching region of OH groups has been used to gain insight into composition-dependent structural changes in the crystals. The results demonstrate that, characteristically, the OH groups occupy different sites in the doped and congruent LiNbO crystals and have different quasielastic O-H bond constants in their structure. In stoichiometric lithium niobate crystals, all of the OH sites and quasi-elastic O-H bond constants are identical. At threshold Zn and Mg dopant concentrations, the frequencies, widths, and intensities of the observed lines change sharply. The linewidths in the spectra of the LiNbO:Zn crystals near their first concentration threshold (≈2.0 mol % ZnO) and the LiNbO:Mg crystals near their first and second concentration thresholds (≈3.0 and 5.5 mol % MgO) decrease markedly, indicating ordering of the position of the OH groups in the structure of the crystals. [ABSTRACT FROM AUTHOR]

LiNbO:ZnO (3.43-5.84 mol %) crystals have been studied using Raman spectroscopy and fullprofile analysis of X-ray diffraction data. The results demonstrate that, at ZnO concentrations above 3.95 mol %, their structure is free of Nb basic defects, which are characteristic of congruent lithium niobate crystals. Increasing the Zn concentration leads to changes in the arrangement of structural units in the cation sublattice along the polar axis and distorts the BO (B = Nb, Li, Zn, or a vacancy) oxygen octahedra. In the Raman spectra of the crystals, the width of the line at a frequency of 876 cm, which corresponds to stretching modes of the oxygens in the BO octahedra, has been shown to increase considerably, which may be due to changes in the character of bonding in the B-O-B bridges in response to changes in the Zn concentration in the crystals. The gradual increase in the electro-optical coefficients of the LiNbO:ZnO crystals with increasing zinc concentration can be accounted for by changes in the ionic contribution to these bonds. [ABSTRACT FROM AUTHOR]

The effect of Sc and Sc + Zr on the structure and properties of Al-Mg-Si alloys is studied using the methods of hardness measurement, resistivity, mechanical properties, and light and electron microscopy. A considerable strengthening of Al-MgSi alloys doped with transition metals (Sc or Sc + Zr) during natural aging and its almost complete absence during artificial aging are established. The observed effects are explained using electron microscopy and local X-ray analysis. [ABSTRACT FROM AUTHOR]

We have studied arsenic incorporation from tris(dimethylamino)arsine into epitaxial CdTe layers in a metalorganic chemical vapor deposition (MOCVD) process. Arsenic incorporation into the layers has been shown to depend on the crystallographic orientation of their growth. Incorporation effectiveness increases in the order (111)B < (211)B < (100) < (310) < (211)A. Arsenic concentration in the CdTe layers is proportional to the tris(dimethylamino)arsine flow rate to the power 3/2. The dependence of arsenic incorporation on the ratio of the metalorganic tellurium and cadmium precursors in the vapor phase suggests that arsenic is incorporated predominantly into the anion sublattice. The maximum concentration of free charge carriers, p = (1-2) × 10 cm, was observed after annealing of the arsenic-doped CdTe layers in an argon atmosphere. [ABSTRACT FROM AUTHOR]

We have studied the effect of magnesium added to the starting mixture as MgS or MgCl on the performance characteristics of synthesized ZnS:Cu,Mn phosphor powders. It has been shown that the incorporation of certain amounts of magnesium into the ZnS:Cu,Mn phosphor leads to an increase in photo- and electroluminescence brightness and is favorable for Mn incorporation into the structure of the phosphor. In particular, additional doping of a dc electroluminescent ZnS:Cu,Mn phosphor with 30 mol % Mg ensured not only a shift of its luminescence spectrum to shorter wavelengths, thereby extending the color range of light sources, but also a twofold increase in its brightness. [ABSTRACT FROM AUTHOR]

Nanocrystalline gallium- and indium-doped zinc oxide samples have been prepared through coprecipitation from aqueous solutions. Acid centers on the surface of the materials have been investigated using temperature-programmed desorption and IR spectroscopy. The results demonstrate that, with increasing dopant concentration, the density of OH groups on the surface of ZnO〈Ga〉 and ZnO〈In〉 increases and the contribution of cation centers to surface acidity decreases. The interaction of the material with oxygen has been studied using in situ electrical conductivity measurements. Doping of zinc oxide with gallium or indium has been shown to increase the percentage of molecular chemisorbed oxygen species on the surface of the material. [ABSTRACT FROM AUTHOR]