Octahedral Positions Research Articles

Timing of pegmatite emplacement and skarn formation in the Malyovitsa Unit, NW Rila: evidence from zonal grossular crystals

Contact Ca-skarns are formed in the marbles of the Malyovitsa Lithotectonic Unit as a result of emplacement of crosscutting pegmatite injections in the area of the Dzhendemski Ezera, NW Rila Mt. Large (up to 4 cm), well-shaped garnet crystals dominate the mineral association with additional vesuvianite, diopside, scapolite and zoisite. Garnets were selected for mineralogical, geochemical and U-Pb geochronological study. Their crystals show clear zonal pattern due to variation in the octahedral position (Fe3+/Al3+), although the overall composition defines grossular predominance (72–95 mol.% grossular; 4–24% andradite). Trace-element signatures reveal constant isomorphic incorporation of P, V, Zn, Ga, Ge and Y, REE, HFSE, U. Results from the in-situ U-Pb dating of the studied skarn materials suggest the timing of pegmatite intrusion onto the metamorphic rocks and marble-hosted skarn formation at 58.37±0.70 Ma.

Order of osakaite–namuwite–lahnsteinite formation during alkalization of sulfate solutions

Experiments with dropwise alkalization of a 0.1 M ZnSO4 solution with 1M NaOH were carried out to establish the formation order of Zn-hydroxy-sulfate minerals (osakaite, namuwite, and lahnsteinite). During the controlled alkalization with 1M NaOH of a 0.1M ZnSO4 solution, namuwite (osakaite), lahnsteinite and wulfingite are successively formed. The obtained precipitates were characterized by powder X-ray diffraction (XRD) and SEM-EDS methods. The formation conditions and regions of stability of osakaite and namuwite are at near circumneutral pH (6.5–7), while lahnsteinite is stable at high pH (11–12). This explains the wider distribution of namuwite and osakaite in nature. The isomorphic substitution of Zn2+ cation with Cu2+ in the hydroxide layer of the Zn-hydroxy-sulfate minerals during controlled alkalization was studied using mixed 0.1M ZnSO4 + CuSO4 solution (molar ratio Zn:Cu = 4:1 and 1:1). During controlled alkalization of mixed Zn-Cu sulfate solutions, 25% copper cations are isomorphic incorporated in the namuwite (osakaite) and lahnsteinite structures. It was determined that this Cu2+ content is the upper limit of the isomorphism and corresponds to the occupation of 1/3 of octahedral positions.

Effect of Fe-Doping on Thermal Expansion and Stability of Bismuth Magnesium Tantalate Pyrochlorere.

A continuous series of solid solutions (Bi1.5Mg0.75-xFexTa1.5O7±Δ (x = 0-0.75)) with the pyrochlore structure were synthesized with the solid-phase method. It was shown that iron, like magnesium, is concentrated in the structure in the octahedral position of tantalum. Doping with iron atoms led to an increase in the upper limit of the thermal stability interval of magnesium-containing pyrochlore from 1050 °C (x = 0) up to a temperature of 1140 °C (x = 1). The unit cell constant a and thermal expansion coefficient (TEC) increase uniformly slightly from 10.5018 Å up to 10.5761 Å and from 3.6 up to 9.3 × 10-6 °C-1 in the temperature range 30-1100 °C. The effect of iron(III) ions on the thermal stability and thermal expansion of solid solutions was revealed. It has been established that the thermal stability of iron-containing solid solutions correlates with the unit cell parameter, and the lower the parameter, the more stable the compound. The TEC value, on the contrary, is inversely proportional to the cell constant.

Sol-Gel Synthesis and Characterization of Yttrium-Doped MgFe2O4 Spinel.

In this study, an environmentally friendly sol-gel synthetic approach was used for the preparation of yttrium-doped MgFe2O4. Two series of compounds with different iron content were synthesized and A-site substitution effects were investigated. In the first series, the iron content was fixed and the charge balance was suggested to be compensated by a partial reduction of Fe3+ to Fe2+ or formation of interstitial O2- ions. For the second series of samples, the iron content was reduced in accordance with the substitution level to compensate for the excess of positive charge, which accumulates due to replacing divalent Mg2+ with trivalent Y3+ ions. Structural, morphological and magnetic properties were inspected. It was observed that single-phase compounds can only form when the substitution level reaches 20 mol% of Y3+ ions and iron content is reduced. The coercivity as well as saturation magnetization decreased with the increase in yttrium content. Mössbauer spectroscopy was used to investigate the iron content in both tetrahedral and octahedral positions.

Magnetic properties of CaCu3-xTi4-yFex+yO12 solid solutions: Valence state of iron ions and metamagnetic phase transitions

CaCu3-xTi4-yFex+yO12 (1 or 3%) solid solutions were synthesized using a solid state method, while 1 or 3 mas. % of iron (natural abundance of isotopes) was added to the stoichiometric amount of CaO, CuO and TiO oxides. CaCu3-xTi4-y57Fex+yO12 (3%) sample with a higher 57Fe isotope content was synthesized using the same technology for the detailed investigation by the Mӧssbauer spectroscopy. The structural and microstructural characteristics of calcium copper titanate samples were studied by X-ray diffraction, X-ray fluorescence analysis and scanning electron microscopy techniques. The magnetic properties were studied by Mӧssbauer spectroscopy, electron spin resonance and magnetometry methods. Based on all experimental data we can conclude that Fe ions substitute Ti4+ and Cu2+ positions in octahedral and planar oxygen environment, respectively. Such type of substitution leads to the appearance of three types of iron magnetic centers: divalent Fe2+ in the planar environment and trivalent Fe3+ in the symmetrical and distorted octahedral positions that strongly effects to the magnetic properties of the investigated samples. Most unique magnetic properties including the metamagnetic phase transitions are observed in CaCu3-xTi4-yFex+yO12 (3%) sample where both the significant amount of Fe3+ ions in distorted octahedral position together with Fe2+ are present.

The impact of yttrium aluminum garnet stoichiometry deviation on the conversion efficiency of tetravalent chromium ions

In this work, the conversion efficiency of Cr4+ ions and the optical properties of ceramics based on chromium-doped yttrium aluminum garnet were investigated. Increasing the conversion efficiency of Cr3+ to Cr4+ opens up broad prospects for using YAG ceramics as saturable absorbers for passive Q-switching of Nd- and Yb-solid-state lasers. The aim of this work was to study the effect of magnesium oxide concentration on the conversion efficiency of Cr3+ to Cr4+ under conditions of Al3+ (4.8 mol.%) and Y3+ (2.9 mol.%) cations excess in the garnet structure as well as the stoichiometric ratio Y3+/Al3+ = 3/5. The possibility of changing the concentration of Cr4+ ions in both the octahedral and tetrahedral positions due to the formation of magnesium substitution defects when the composition deviates from the yttrium-aluminum garnet stoichiometry has been studied. Chromium-doped transparent optical ceramics based on yttrium-aluminum garnet with different ratios of Y3+/Al3+ cations was obtained by the two-stage coprecipitation method. Magnesium oxide was used as a sintering additive and charge compensator for converting chromium ions from the trivalent to the tetravalent state in concentrations of 0 to 0.2 wt.%. It was found that aluminum excess in the yttrium-aluminum garnet matrix leads to a decrease in the Cr3+ to Cr4+ conversion efficiency. A deviation of stoichiometry towards an excess of yttrium leads to a decrease of air annealing temperature for oxidizing chromium ions to the tetravalent state and their transition to the tetrahedral position. However, the samples optical transmittance with an excess of yttrium was lower than in the cases of an excess of aluminum and stoichiometry. It was found that with an increase in the vacuum sintering temperature from 1780 to 1820 °C in the samples with an excess of aluminum, an increase in the concentration of Cr4+ ions in the tetrahedral position occurs, as evidenced by higher absorption intensity at a wavelength of 1030 nm. For the cases of stoichiometry and an excess of yttrium in garnet, this effect is less pronounced. Samples of optical ceramics of yttrium-aluminum garnet with a light transmission of more than 75 % in the visible and near-IR ranges with pronounced absorption bands of chromium have been obtained. The results of the work can be applied to the creation of passive switches for solid-state lasers.

Preparation and structure analyses of Sn-bentonite for pertechnetate removal

Tin (Sn) -bentonite was prepared by ion exchange method from Ca-bentonite. For the ion exchange process, tin-chloride (SnCl2) solution was prepared from metallic tin, and the tin concentration was determined by Microwave Plasma Atomic Emission Spectroscopy (MP-AES). Sn-bentonite was characterized by X-ray fluorescence spectrometry (XRF), X-ray powder diffraction (XRPD), X-ray photoelectron spectroscopy (XPS) and 119Sn as well as iron-57 (57Fe) Mössbauer spectroscopy. 119Sn Mössbauer spectroscopy and XPS undoubtedly revealed both Sn+2 and Sn+4 ions in Sn-bentonite. SnII was attributed to be incorporated into the interlayer space while SnIV located partly in the octahedral position and in the interlayer space of montmorillonite. The removal of radioactive pertechnetate anion (99mTcO4-) was studied on Sn-bentonite in aqueous and artificial urine media. Based on the measurement results, 99mTcO4- ion can be removed, in case of aqueous media, the equilibrium is reached after 5 mins (x = 99.9 ± 0.01%, k = 4.2 ± 0.83 1/min) (Buzetzky et al., 2019), while in the case of urine media the equilibrium is reached after 30 mins (x = 59.1% ± 2.7, k = 0.18 ± 0.05 1/min). Pertechnetate anoin sorption on tin-bentonite is a (Sn(II/IV)-TcO4-) redox reaction. Thus, Sn-bentonite can be a suitable sorbent for radioactive waste management.

Sm3+ doped Mn-Zn mixed ferrites: Synthesis and characterization

Pure and Samarium (Sm3+) doped Mn-Zn ferrites were synthesized using Co-precipitation method. The Sm3+ concentration varied from 0.1% to 0.3%. This was added to the solution during the synthesis of Mn-Zn ferrites (Mn0.5Zn0.5Fe2O4) at room temperature. The precipitate so obtained was annealed at 200℃ for 4 h and then crushed to powder. The powdered material was subjected to structural, morphological, compositional, optical and magnetic characterization. XRD shows cubic spinal structure with crystallite size of the order of 6 nm. TEM and SEM images show spherical particles are in good agreement with XRD data. EDAX indicates stoichiometry of elements present in material. FTIR shows various functional groups and doped samarium. VSM for pure Mn:Zn ferrite show hysteresis with high magnetization, coercivity and low remanence. All the magnetic parameters decrease on 0.1% Sm3+ doping. These parameters get increased, compared to values at 0.1% doping, on increasing Sm3+ doping to 0.2%. On further increasing Sm3+ doping to 0.3%, the magnetic parameters show insignificant changes. VSM shows that Sm3+ affects magnetic properties significantly only at lower doping concentrations. These changes are due to Sm3+ substitution at tetrahedral and octahedral positions. The ionic radii mismatch in between Samarium and iron influence the magnetic parameters of Mn0.5Zn0.5Fe2O4.

Influence of Ce-Mn co-doping on the structure and magnetic properties of cobalt ferrites

In this study, we selected Ce3+ and Mn2+ as co-doped ions in order to improve the magnetic properties of cobalt ferrite. The nominal composition Co1−xMnxFe2−xCexO4 (x = 0, 0.05, 0.10, and 0.20) nanoparticles were prepared by facile co-precipitation technique, and the effect of co-doping content on the structural and magnetic properties of cobalt ferrite was investigated. The structural result confirmed the formation of cubic spinel structure for all co-doped samples, although secondary phase of CeO2 was detected in the high co-doping content ones. Fourier transform infrared spectroscopy confirmed the presence of metal-oxygen bonding. All samples exhibited two frequency bands corresponding to the phonon vibrational stretching in the octahedral and tetrahedral lattice positions, respectively. The surface morphology analysis revealed the spherical shape of the ferrite nanoparticles. After co-doped with Ce3+ and Mn2+ ions, the magnetic parameters of cobalt ferrite were significantly improved. The maximum magnetization saturation is 66.5 emu/g when x = 0.05, and the maximum coercivity is 2288 Oe when x = 0.10. The two values are approximately 29% and 47% higher than that of the un-doped one. At the same time, the maximum energy product reaches 0.72 MG·Oe, which is about 118% higher than that for pure cobalt ferrite, i.e. 0.33 MG·Oe. The reasons may be related to the substitution of Fe3+ and Co2+ with Ce3+ and Mn2+, and also the resulting changes in crystallite sizes of the samples. These results demonstrate the effectivity of Ce-Mn co-doping in improving the magnetism of cobalt ferrite.

Evidence of two Yb3+ crystallographic sites occupancy in Y3Al5O12 ceramics from an in depth spectroscopic analysis

In this paper a complete spectroscopic analysis of low-temperature absorption and emission spectra of 10 ​at.% Yb:YAG ceramic are investigated. On the basis of the analysis of the temperature dependences of individual spectral lines (from 10 ​K to 300 ​K), as well of the joint analysis of the Raman spectra and the temperature-resolved absorption and emission spectra a two center model of Yb3+ doping ion is proposed. Namely, most of the ytterbium ions replace yttrium ions in dodecahedral positions (c-site), while a small part replaces yttrium ions in octahedral positions (a-anti-site).

Effect of rare earth (Nd3+) metal doping on structural, morphological, optical and magnetic traits of Zn–Mg nano-ferrites

Herein, we report the synthesis of Zn0.7Mg0.3NdxFe2–xO4 (where, x = 0.0, 0.01, 0.02) ferrite nanoparticles by employing the sol–gel auto-combustion technique. The X-ray diffraction (XRD) pattern suggests the formation of a pure cubic structure, without any impurity phase, with an Fd3m space group at room temperature. With increasing doping amount, the crystallite size is reported as 35–41 nm, while the lattice parameters rise from 0.8381 to 0.8395 nm. Field emission scanning electron microscopy (FESEM) images show the formation of spherical grains with agglomerated morphology in all the samples, with grain sizes ranging from 49 to 103 nm. Energy dispersive X-ray spectroscopy (EDX) and elemental mapping investigation confirm the chemical purity of all the samples. Fourier transform infrared (FTIR) analysis shows the presence of two prominent peaks around 440 and 560 cm−1 that correspond to the octahedral and tetrahedral positions. In addition, the existence of five Raman active vibrational modes in all produced specimens again confirms the structural purity of all the samples. The M−H curve shows that saturation magnetization (Ms) first increases from 14.98 to 28.22 emu/g and then decreases to 18.98 emu/g with increasing doping amount. This is due to the A-B type super-exchange interaction for the synthesized samples. The variation in coercivity (Hc) and magnetic anisotropy (K1) suggest the thermal stability of all the samples and can be utilized in transformers and solenoids.

Stable garnets in the Er2O3–Sc2O3–Al2O3 oxide system for optical ceramics application

Erbium-scandium-aluminum garnets (ErSAG) with the maximum possible concentrations of scandium cations in the dodecahedral and octahedral positions of the crystal lattice have been synthesized. It has been established that in ErSAG at a temperature of 1600 °C the maximum possible concentration of scandium in the dodecahedral and octahedral position reaches 64.7 ± 2.0 at. % and 92.0 ± 2.0 at. %, respectively. The maximum possible concentrations of scandium cations in the dodecahedral position and the set of range of possible ErSAG compositions decrease at increasing of calcination temperature. It was shown that ceramics technique allow to produce the optical ceramics with compositions {Er1.5Sc1.5}[Sc0.2Al1.8](Al3)O12 (SAG: Er 50 at%) and {Y1.57Er0.03Sc1.4}[Sc0.2Al1.8](Al3)O12 (YSAG: Er 1 at%), which can be considered as analogs of yttrium-aluminum garnet single crystals (YAG: Er 50 at% and YAG: Er 1 at%).

Effect of Zn2+ substitution on magnetic properties of the quasi-one-dimensional spin chain compound Ca3CoMnO6

The subtle variation of magnetic structure has large influence on the macroscopic magnetism of Ca3CoMnO6. As the isovalent nonmagnetic ions have no exchange interaction with the adjacent Co2+/Mn4+ and it could keep the valence states and spin states of the Co/Mn ions unchangeably. Introduction of isovalent nonmagnetic ions thus becomes an ideal selection for us to understand the relevant micromechanism. In this paper, a series of Zn2+ substituted Ca3Co1-xZnxMnO6 (0 ≤ x ≤ 0.2) samples were prepared, and the microstructure and magnetic properties were investigated in detail. The XRD results indicate that for low doped samples the larger radius of Zn2+ causes the lattice parameters and volume increase. While for high doped samples the Zn2+ ions enter the octahedral position, resulting in shrinkage of the lattice. The introduction of Zn2+ ions could also influence the magnetic structure of Ca3CoMnO6 effectively. A small amount of nonmagnetic Zn2+ ions well decrease the concentration of the intrinsic defects and help to form more short-range magnetic order. But as the Zn2+ doping concentration increases, the main effect of Zn2+ doping is to release the magnetic frustration of Ca3CoMnO6, and finally a more robust long range antiferromagnetic structure can be established in high doped samples. Simultaneously, the subtle variation of magnetic structure with Zn2+ substitution leads the Ca3Co1-xZnxMnO6 samples present different dynamic behaviors. This interesting finding could serve as a new reference for tuning the magnetic ordering of Ca3CoMnO6 and improving its multiferroic properties.

Weathering crusts and their role in formation of post-kimberlite sedimentary sequences

The principal suppliers of terrigenous material to forming ancient diamond placers are characterized based on the main diamond-bearing districts of the Siberian platform as an example. A special attention is paid to characteristics of the local sources of allothigenous material washed out into sedimentation basins of the period specified, the main of which were weathering crusts formed upon terrigenouscarbonate rocks, trappean formations (dolerites, tuffs, and tuffaceous rock sequences), and kimberlites. A comprehensive comparative investigation of the ancient weathering crusts upon the rocks of various chemical and mineralogical composition allowed tracing the specific features of their hypergene alteration and the typomorphic indications of the eluvial products. The same varieties of primary minerals in redeposited products of weathering of the various rocks may be differentiated at the structural level, and the secondary phyllosilicates may be identified either by occupation of the octahedral positions in their structure, or by mutual superposition of individual silicate layers, or by their polytypic character. Redeposition of the products of weathering of the rocks of various composition near the denudation areas and their predominant accumulation in freshwater basins, as well as a small thickness of the sedimentary layers formed and their insignificant burial, had determined a weak hydrodynamic impact of the environment on the allothigenous minerals (argillaceous, first of all), which did not lead to their sufficient diagenetic alteration. Therefore, the products of various types of the weathering crusts, redeposited in the ancient sedimentary sequences, retain the structural and crystal-chemical peculiarities in relation to the minerals of the eluvial rock masses, which allows tracing the ways of arrival of the terrigenous (including diamondiferous) material into the sedimentation basins.

Synthesis and Characterisation of Mg2+ and Al3+ Co-Doped CoCr2O4 Inorganic Pigments With High Near-Infrared Reflectance

A new class of near-infrared (NIR) reflectance pigments based on Co1−xMgxCr2−yAlyO4 (x = 0–1 and y = 0–2) was synthesised using the Pechini-type sol-gel process. The developed powders were characterised by thermogravimetry and differential scanning calorimetry, X-ray diffraction (XRD), ultraviolet–visible near-infrared diffuse reflectance spectroscopy, and colour Commission Internationale del'Eclairage (CIE) 1976 (L*a*b*) colour scales. The XRD patterns revealed characteristic peaks of the spinel structure with good crystallinity. Substituting Mg2+ for Co2+ ions in the tetrahedral positions and Al3+ for Cr3+ ions in the octahedral positions of CoCr2O4 reduces the cost and changes the colour of the pigment (green to yellow and then blue). Moreover, the synthesised pigments exhibited high NIR solar reflectance in the 780–2,500 nm wavelength range. The thermal and chemical stability of the pigments was also studied. Our findings demonstrate the potential for applying these pigments in cool colourants.

Optimizing the eg occupancy of magnesium cobalt spinel oxides via Fe substitution to promote oxygen evolution reaction

Cobalt-based spinel oxides are a promising class of electro-catalysts for oxygen evolution reaction (OER). Herein, a series of Mg(Co1−xFex)2O4 (x = 0.0–1.0) oxides are designed as OER catalysts. MgCo2O4 is selected to fix Co3+ in the octahedral position, which is active site for the OER. We elucidate the volcanic relationship between the OER activity and Fe substitution concentration in Mg(Co1−xFex)2O4, which shows an optimal activity at 20 at% Fe substitution. Superconducting Quantum Design (SQUID) technique reveals that Fe substitution tunes the eg orbital electronic configuration of Co3+ from low spin to high spin. The optimized eg occupancy of 0.91 is obtained in MgCo1.6Fe0.4O4. Density functional theory calculations verify that the improved OER performance stems from the enhanced Co-O covalence after Fe substitution, which promotes the transfer of electrons from oxygen, thus accelerates the catalytic oxygen evolution reaction. The formation energy of O* decrease as well by Fe substitution, and the conversion of OH* into O* is identified to be the rate-determining step. This work complements the optimizing electronic configuration of cobalt cations for OER and provides favorable principles for the rational design of OER electro-catalysts.

Micropowder Ca2YMgScSi3O12:Ce Silicate Garnet as an Efficient Light Converter for White LEDs.

This work is dedicated to the crystallization and luminescent properties of a prospective Ca2YMgScSi3O12:Ce (CYMSSG:Ce) micropowder (MP) phosphor converter (pc) for a white light–emitting LED (WLED). The set of MP samples was obtained by conventional solid-phase synthesis using different amounts of B2O3 flux in the 1–5 mole percentage range. The luminescent properties of the CYMSSG:Ce MPs were investigated at different Ce3+ concentrations in the 1–5 atomic percentage range. The formation of several Ce3+ multicenters in the CYMSSG:Ce MPs was detected in the emission and excitation spectra as well as the decay kinetics of the Ce3+ luminescence. The creation of the Ce3+ multicenters in CYMSSG:Ce garnet results from: (i) the substitution by the Ce3+ ions of the heterovalent Ca2+ and Y3+ cations in the dodecahedral position of the garnet host; (ii) the inhomogeneous local environment of the Ce3+ ions when the octahedral positions of the garnet are replaced by heterovalent Mg2+ and Sc3+ cations and the tetrahedral positions are replaced by Si4+ cations. The presence of Ce3+ multicenters significantly enhances the Ce3+ emission band in the red range in comparison with conventional YAG:Ce phosphor. Prototypes of the WLEDs were also created in this work by using CYMSSG:Ce MP films as phosphor converters. Furthermore, the dependence of the photoconversion properties on the layer thickness of the CYMSSG:Ce MP was studied as well. The changes in the MP layer thickness enable the tuning of the white light thons from cold white/daylight to neutral white. The obtained results are encouraging and can be useful for the development of a novel generation of pcs for WLEDs.

Co substituted Ni–Zn ferrites with tunable dielectric and magnetic response for high-frequency applications

Microwave ferrites are the most promising materials for high frequency and high-power devices. In this work, Co substituted Ni–Zn ferrites (Ni0.5-xZn0.5CoxFe2O4; x = 0–0.4) are synthesized, and the structural, morphology, dielectric, magnetic response are systematically investigated. The X-ray diffraction pattern (XRD) pattern confirmed the formation of pristine cubic phase alone without any secondary phase in all the samples. Substitution of Co2+ resulted in increased crystallite size and lattice constant. Raman peak intensity is suppressed, and a shift towards a lower wavenumber is observed with Co substitution. The change in position and intensity is analyzed and attributed to the change in cationic distribution in tetrahedral and octahedral positions by deconvoluting the Raman peaks. The Energy-dispersive X-ray spectroscopy (EDAX) analysis confirms the stoichiometry of compounds. The real permittivity and tan δ are decreased with the dilution of Co (x = 0: ε' = 24, tan δ = 0.015; x = 0.4: ε' = 11, tan δ = 0.035 @ 1 MHz). Further, permeability initially increased in the X band frequency range and decreased with increasing Co concentration. An increase in the saturation magnetization was observed initially with increased Co content and a decrease after x = 0.2. A maximum saturation magnetization (Ms = 63.3 emu/g) observed for x = 0.2 composition. Interestingly, a giant coercivity and high effective magnetocrystalline anisotropy are observed with the incorporation of Co at low temperatures (5 K). The low dielectric loss, high saturation magnetization, and low coercivity at room temperature of Co substituted Ni–Zn ferrites suggest that these compounds are potential candidates for high-frequency devices (circulators).

Impact of Y2O3 on the structural, optical, radiation shielding, and ligand field parameters of transparent borate glass containing constant CrO3 and high Na2O contents

This study aims to investigate the impact of the rare earth element yttrium on the optical properties of chromium (Cr)-doped borate glasses. A series of borate glasses (labeled as BNaCrY glasses) were prepared and studied, each with a constant amount of chromium trioxide (CrO3) but doped with varying amounts of yttrium oxide (Y2O3). Infrared analysis revealed four distinct spectral areas in the internal structure of all BNaCrY glasses. Optical absorption spectra were used to investigate the impact of Y2O3 doping on the optical transitions of BNaCrY glasses. The presence of Cr cations caused the appearance of an absorption band at 379–383 nm, which overlapped with the Urbach edge that is commonly given an edge-like at 430 nm. The Urbach edge has been manifested through a full deconvolution attempt. Cr cations in the Cr3+ state were confirmed by visible absorption bands and are nestled in the octahedral positions. The band at 574–593 nm was used to determine the crystal field splitting (10Dq) for all BNaCrY glasses. Due to the increased number of O anions around the Cr cation, the values of 10Dq increased with Y2O3 doping. The remarkable increase in 10Dq was attributed to increased interaction between Cr cations and their surroundings. In contrast, the shielding parameters were taken into account when evaluating the ability of these transparent glasses to protect against nuclear radiation. We found that the sample with the highest Y2O3 concentration had the highest linear attenuation coefficient and the lowest half-value layer. Thus, BNaCrY glasses are more efficient as attenuators than commercial glasses (such as the Rider and Osmania glasses), especially at low photon energies.

A hybrid density functional design of intermediate band semiconductor for photovoltaic application based on group IV elements (Si, Ge, Sn, and Pb)-doped CdIn2S4

The CdIn2S4 semiconductor is considered a potential host for the implementation of intermediate band solar cells due to its ideal bandgap value and excellent photoelectric property. In this paper, the electronic structures of group IV elements (Si, Ge, Sn, and Pb)-doped CdIn2S4 have been investigated by using hybrid density functional calculations. In the case of Ge, Sn, and Pb doping, an isolated and partially occupied intermediated band with delocalized characteristics could be created in the bandgap of the host. The results of the projected density of states reveal that the intermediated band is derived from the hybridization between the S-3p and dopant-ns states. Thanks to the assistance of the impurity band, the optical absorption ability of the intermediate band semiconductor is greatly enhanced. Based on the detailed balance theory, the theoretical efficiencies of intermediate band solar cells made by Ge- and Pb-doped CdIn2S4 are estimated to be 45.0% and 49.2%, respectively, which are superior to the Shockley and Queisser limit (40.7%) of a single junction photovoltaic device. Moreover, the experimental synthesis of these impurity semiconductors is relatively feasible because substitutional doping at the octahedral position is energetically favorable. These findings would be helpful to the development of a high-efficiency intermediate band solar cell.