Ca Substitution Research Articles

Effects of Fe-Ca-Mg substitutions on the equation-of-state of pyrope-rich garnet from ab initio modeling and experiments: Insights and implications for the upper mantle

We report systematic first-principles results of structural properties and compression behavior based on density functional theory (DFT) and an exchange-correlation functional for solids, of Al-bearing garnets of general compositions in the pyrope-almandine-grossular solid solution system. The combination of DFT and a simple solid solution model is able to produce a compositional dependence of the compression curve consistent with trends observed in experimental studies. Using end-member properties extrapolated from our computations and perturbing an extant thermodynamic model we observe only marginal effects on the bulk sound velocity of pyrolite and MORB along relevant geothermal paths. However, this could hide important effects on the elemental partitioning between garnet and other major phases which should be further investigated both experimentally and computationally. We also present simulations of the effect of combined Fe and Ca substitutions for Mg on the elastic tensor of Al-bearing garnets, our simplified modeling shows only partial agreement with the trends observed in experiments. Therefore, further computational investigations, especially of the effect of Fe-Mg substitution on the tensor, are needed.

Case study of fluorite mineralization using traditional and laser spectroscopic techniques, homret akarem area south eastern desert, Egypt

Green fluorite samples from Homret Akarem, eastern desert Egypt, were investigated by laser-based Raman spectroscopy to study the effect of rare earth elements (REEs) and natural radiation from the surrounding environment on their physico-chemical properties, taking into consideration the geological setting. Geochemical data of trace elements display fluorite enrichment with Y, Pb, Sr, Sn, and other REEs. XRD showed lattice parameters with values higher than those for synthetic fluorite due to the substitution of Ca by Sr and less likely by radiation from U. A considerable shift in the binding energy (BE) for Ca and F obtained from the XPS spectrum indicates that U carried by the hydrothermal solutions formed a discontinuous thin film on the surface of fluorite. Laser-Raman spectroscopy showed strong peaks below 500 cm−1 and both shallow and weak peaks above 500 cm−1. The strong peaks indicate that the substitution of Ca by Sr, point defects, and natural radiation caused by U have a stronger effect on the crystal structure than REEs. Raman spectroscopy supported the initial reports of uranium minerals like Rutherfordine, Kasolite, Soddyite, and Uranophane-alpha.

Temperature sensing performance of M2La8(SiO4)6O2:Ce3+(M=Ca, Sr, Ba) based on fluorescence intensity ratio of dual emission centers in different coordination environments

Rare earth doped luminescent sensing materials as non-contact thermometers have attracted extensive research interests due to their wide applications in areas like military, medical care, aerospace, etc. How to expand the working temperature range and improve the sensitivity has become the focus. In this work, we synthesized a series of apatite-structured luminescent temperature sensors M2La7.9Ce0.1(SiO4)6O2 (M = Ca, Sr, Ba) via isomorphic substitution. By monitoring the differential changes of emission intensities from Ce3+ at the 7-coordinate and 9-coordinate site respectively when temperature varies, the real-time temperature can be determined. These materials were proven to possess the maximum absolute sensitivity up to 0.825 × 10−3 K−1, 2.63 × 10−3 K−1 and 4.33 × 10−3 K−1, respectively. Meanwhile interesting regular patterns were observed for their temperature sensitivities with the substitution of Ca, Sr and Ba. Furthermore, through studying the temperature sensitivity of Ba2La8(SiO4)6O2:xCe3+ samples with different concentrations, it was found that when the Ce3+ content was at the optimal doping concentration of 0.7, the absolute sensitivity of the sample reached 14.64 × 10−3 K−1 at 573 K. This finding has opened up a new avenue for designing fluorescent temperature sensors.

DPPH radical scavenging assay: A tool for evaluating antioxidant activity in 3 % cobalt – Doped hydroxyapatite for orthopaedic implants

In the present work, the 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging assay was used to examine the antioxidant activity of hydroxyapatite (HAP) and of 3 % cobalt doped HAP (Co-HAP). The DPPH assay revealed that 3 % Co-HAP had significant DPPH radical scavenging activity. Co-HAP was synthesised using the sol-gel method, and its characteristics were assessed using energy-dispersive X-ray spectroscopy (EDS), Field emission scanning electron microscopy (FESEM), Fourier-transform infrared spectroscopy (FTIR), and X-ray diffraction (XRD). As the ionic radius of Co is smaller than Ca ion, XRD study reveals that crystallite size reduces from 40.82 nm to 24.91 nm after incorporation of Co into HAP implying substitution of Ca by Co ions. Compared to ascorbic acid, Co-HAP showed exceptional antioxidant potential and, at some doses, even outperformed ascorbic acid in scavenging capability. Notably, the IC50 value for pure HAP was 35, whereas it was substantially lower for Co-HAP at 20.85, indicating that it has stronger antioxidant properties. According to these results, 3 % Co-HAP has much potential for biomedical uses, especially in tissue engineering biomaterials and antioxidant-based therapeutics. Its capacity to prevent diseases brought on by oxidative stress and encourage tissue regeneration makes it a promising option for additional biomedical research.

Influence of K ions on CaO-SiO2-KO2 melt structure and diffusion coefficients studied by molecular dynamics simulations

Molecular dynamics simulations were employed to investigate the influence of replacing equimolar CaO with K2O in CaO-SiO2-K2O melts. The study reveals that Si-O primarily adopts a tetrahedral form, and the introduction of K2O expands the distance between network structures, increasing average bond lengths for Ca-(O)-Si and K-(O)-Si. The coordination number for K-(O)-Si consistently exceeds that for Ca-(O)-Si, suggesting that K+ exerts a more significant modification influence on the network structure. The substitution of Ca2+ with K+ does not disrupt the [SiO4]4− tetrahedral structure, as evidenced by unchanged O-Si-O bond angles. Calculations of ionic diffusion capabilities demonstrate that DK>DCa>DO>DSi. Calculations show K+ enhances ionic diffusion, explaining the improved macroscopic fluidity. Raman spectroscopy verifies the accuracy of molecular dynamics simulations by confirming the unchanged degree of microstructural aggregation in the CaO-SiO2-K2O melt.

Mechano-luminescence of Eu2+, Dy3+ co-doped strontium aluminate phosphors with the substitution of calcium ions

Mechano-luminescent material can emit light under various external mechanical forces such as pressure, friction, impact and ultrasound. Elastic-luminescent materials have the property that the light signal increases linearly with the increase in stress and has been widely applied. A series of strontium aluminate/strontium calcium samples doped together with europium and dysprosium have been prepared by a high-temperature solid-state method. The effect of strontium/calcium ratio on the crystal structure and luminescence property of the samples have been systematically studied. With the increase of Ca substitution, the crystal field environment around divalent europium ions varies which leads to the changes of the emission peaks. The color presented from samples was tuned from green to blue which offers the possibility of color regulation of mechano-luminescence. Among these samples, the elastic-luminescence of the sample Sr0.8Ca0.2Al2O4: Eu2+, Dy3+ shows an excellent performance as the signal increases linearly with the applied pressure, so it has the potential to be used as a pressure sensor.

Effect of Ca substitution on crystal structure and band gap of solar cell material BaSi2

To ameliorate the potential of a promising solar cell material BaSi2, the effects of substituting Ba with Ca atoms on the crystal structure and band gap Eg of BaSi2, were investigated both experimentally and computationally. The solid-solution limit of the Ca atoms in BaSi2 was approximately 2.3 at.%. Single-crystal X-ray diffraction analysis of Ba1−xCaxSi2 (0.025 ≤ x ≤ 0.072) revealed that the unit cell volume decreases with Ca content x, and the Ba atoms at the A1 crystallographic site are preferentially substituted by Ca atoms. Diffuse reflectance measurements indicated that Eg decreases with x (1.24 eV at x = 0 and 1.17 eV at x = 0.07). The density functional theory calculations demonstrate that the experimentally observed decrease in Eg by Ca substitution can be explained qualitatively by the combination of the substitution of Ca atoms in the unit cell volume of BaSi2 and the volume reduction.

DOUBLE-DOPED CALCIUM PHOSPHATE COATINGS WITH ANTIMICROBIAL EFFICACY FOR BIODEGRADABLE METAL BIOMEDICAL IMPLANTS

Over the last decades, biodegradable metals emerged as promising materials for various biomedical implant applications, aiming to reduce the use of permanent metallic implants and, therefore, to avoid additional surgeries for implant removal. However, among the important issue to be solved is their fast corrosion - too high to match the healing rate of the bone tissue. The most effective way to improve this characteristic is to coat biodegradable metals with substituted calcium phosphates. Tricalcium phosphate (β-TCP) is a resorbable bioceramic widely used as synthetic bone graft. In order to modulate and enhance its biological performance, the substitution of Ca2+ by various metal ions, such as strontium (Sr2+), magnesium (Mg2+), iron (Fe2+) etc., can be carried out. Among them, copper (Cu2+), manganese (Mn2+), zinc (Zn2+) etc. could add antimicrobial properties against implant-related infections. Double substitutions of TCP containing couples of Cu2+/Sr2+ or Mn2+/Sr2+ ions are considered to be the most perspective based on the results of our study. We established that single phase Ca3−2x(MˊMˊˊ)x(PO4)2 solid solutions are formed only at x ≤ 0.286, where Mˊ and Mˊˊ—divalent metal ions, such as Zn2+, Mg2+, Cu2+, Mn2+, and that in case of double substitutions, the incorporation of Sr2+ ions allows one to extend the limit of solid solution due to the enlargement of the unit cell structure. We also reported that antimicrobial properties depend on the substitution ion occupation of Ca2+ crystal sites in the β-TCP structure. The combination of two different ions in the Ca5 position, on one side, and in the Ca1, Ca2, Ca3, and Ca4 positions, on another side, significantly boosts antimicrobial properties. In the present work, zinc-lithium (Zn-Li) biodegradable alloys were coated with double substituted Mn2+/Sr2+ β-TCP and double substituted Cu2+/ Sr2+ β-TCP, with the scope to promote osteoinductive effect (due to the Sr2+ presence) and to impart antimicrobial properties (thanks to Cu2+ or Mn2+ ions). The Pulsed Laser Deposition (PLD) method was applied as the coating's preparation technique. It was shown that films deposited using PLD present good adhesion strength and hardness and are characterized by a nanostructured background with random microparticles on the surface. For coatings characterization, Fourier Transform Infrared Spectroscopy, X-ray Diffraction, and Scanning Electron Microscopy coupled with Energy Dispersive X-ray and X-ray Photoelectron Spectroscopy were applied. The microbiology tests on the prepared coated Zn-Li alloys were performed with the Gram-positive (Staphylococcus aureus, Enterococcus faecalis) and Gram-negative (Salmonella typhimurium, Escherichia coli) bacteria strains and Candida albicans fungus. The antimicrobial activity tests showed that Mn2+/Sr2+ β-TCP -coated and Cu2+/Sr2+ β-TCP coated Zn-Li alloys were able to inhibit the growth of all five microorganisms. The prepared coatings are promising in improving the degradation behavior and biological properties of Zn-Li alloys, and further studies are necessary before a possible clinical translation.

Oxide Ion Conduction in Ca-Doped Yb3Ga5O12 Garnet.

Developing oxide ion conductors with new structural families is important for many energy conversion and storage techniques. Herein, a series of Ca-doped Yb3Ga5O12 garnet-type materials are prepared through a traditional solid-state reaction method, with their oxide ion conduction properties being reported for the first time. The results revealed that Ca substitution for Yb would significantly improve the conductivity of Yb3Ga5O12 from 3.57 × 10-7 S/cm at 900 °C under air to 1.66 × 10-4 S/cm, with an oxide ion transporting number of ∼0.52. The oxygen vacancy defect formation energy (∼0.127 eV) and the local structure around an oxygen vacancy were studied by atomic-level static lattice simulations based on the interatomic potential method. The oxide ion conducting mechanism was studied by the bond-valence-based method, which revealed three-dimensional pathways for oxide ion migration in both the parent and Ca-doped structures. The simulated activation energy of oxide ion migration decreased slightly from ∼0.358 eV in the parent structure to 0.346 eV in the doped one. These discoveries in the Ca-doped Yb3Ga5O12 will stimulate extensive exploitation and fundamental research on garnet-type materials.

Enhanced Electrochemical Performance of LaMnO3 Nanoparticles by Ca/Sr Doping

In this paper, the sol-gel method was used to synthesize powders of LaMnO3 (LMO), La0.85Ca0.15MnO3 (LCM), and La0.85Sr0.15MnO3 (LSM). The effect of substituting Ca and Sr at the A-site on the perovskite crystal structure and electrochemical capabilities of LMO was investigated. LCM retained its orthogonal structure in comparison to the parent LMO components, whereas LSM transitioned to a rhombic structure. At 0.5 A/g, the specific capacitance of LCM and LSM electrodes is 185.5 F/g and 248 F/g, respectively. The specific capacitance of LCM was three times greater than that of the LMO electrode. Among the three samples (LMO, 22.25 m2 g−1; LSM, 31.56 m2 g−1), the LCM sample exhibited the highest specific surface area of 38.79 m2 g−1. The charge transfer resistances of the LMO, LCM, and LSM are 0.48 Ω, 0.36 Ω, and 0.38 Ω, respectively. The LCM electrode exhibits the greatest capacitance performance due to its more refined morphology, increased concentration of oxygen vacancy, and more complete utilization of the perovskite bulk structure. The above results demonstrate that Ca or Sr substitution of A-site compounds has great potential for supercapacitor applications.

Study of phase transition behavior and high dielectric properties in [formula omitted] ceramics

In the current work, a full description of the strong effect of Ca substitution in Ba sites of YBa2−xCaxCu3Oδ ceramics prepared by the sol-gel method on structural, electrical, and dielectric properties has been presented. XRD accompanied with Rietveld refinements confirm the significant structural change from orthorhombic phase (Pmmm) for (x = 0) YBa2Cu3Oδ (YBCO) to tetragonal phase for (x = 2) YCa2Cu3Oδ with a P4/mmm spatial group. XPS was performed comparing the two extremums on the Y3d, Cu2p, and O1s, showing a shift in all peaks, confirming the change in structure. SEM study also supports the large change that will take place as Ba sites are substituted by Ca, and the correct stoichiometry of the prepared ceramics was verified with EDS analysis. Such structural changes impact directly transport properties. Temperature-dependent resistivity measurements reveal a superconducting aspect in YBa2Cu3Oδ whereas YCa2Cu3Oδ ceramics are characterized by an insulating to metallic phase transition. The electrical properties in YCa2Cu3Oδ phase is mainly analyzed in terms of the temperature coefficient of resistivity (the TCR effect). YCa2Cu3Oδ ceramics are distinguished by excellent dielectric properties, including a colossal dielectric constant (εr′ ≈ 104) accompanied by low dielectric loss over a wide range of temperatures (298K–448K) and frequencies (10–105 Hz).

Effect of A-Cation Radius on the Structure, Luminescence, and Temperature Sensing of Double Perovskites A2MgWO6 Doped with Dy3+ (A = Ca, Sr, Ba).

Herein, we report a case of A2MgWO6 (A = Ca, Sr, Ba) doped with 2%Dy3+, 2%Li+, in which the influences of the cation substitution are exhibited through the crystal structure, the charge transfer band (O2--W6+), the emission spectrum, the color of the luminescence, and the luminescent decay time. The substitution of Ca2+ and Sr2+ ions for larger ions (Ba2+) led to the crystal structure alteration from cubic to monoclinic and tetragonal, respectively. These structure changes also lowered the crystallography symmetry site of Dy3+, tuned the color of the emitted light from the whitish to yellowish region, and caused a blue shift of the CTB. Furthermore, a significant decline in the lifetime of the 4F9/2 → 6H13/2,15/2 transitions was noticed, from 748, 199, to 146 μs corresponding to Ba, Sr, Ca sample owing to the reduction in the local symmetry of Dy3+. Moreover, the thermal sensing properties of 2%Dy3+-doped samples were investigated based on the fluorescence intensity ratio technique in the range of 80-325 K. Under 266 nm excitation wavelength, the maximum relative sensitivity of the investigated samples was remarkably enhanced from 2.26%/K, 3.04%/K, to 4.38%/K corresponding to Ba, Ca, and Sr samples, respectively. In addition to providing a comprehensive understanding of the effects of compositional modifications on the optical properties, the results also present a viable pathway to manipulate the temperature sensing performance.

Preparation and Characterization of Mono- and Biphasic Ca1-xAgxHPO4·nH2O Compounds for Biomedical Applications.

This study aimed to explore the effects of the full-scale replacement (up to 100%) of Ca2+ ions with Ag1+ ions in the structure of brushite (CaHPO4·2H2O). This substitution has potential benefits for producing monophasic and biphasic Ca1-xAgxHPO4·nH2O compounds. To prepare the starting solutions, (NH4)2HPO4, Ca(NO3)2·4H2O, and AgNO3 at different concentrations were used. The results showed that when the Ag/Ca molar ratio was below 0.25, partial substitution of Ca with Ag reduced the size of the unit cell of brushite. As the Ag/Ca molar ratio increased to 4, a compound with both monoclinic CaHPO4·2H2O and cubic nanostructured Ag3PO4 phases formed. There was a nearly linear relationship between the Ag ion ratio in the starting solutions and the wt% precipitation of the Ag3PO4 phase in the resulting compound. Moreover, when the Ag/Ca molar ratio exceeded 4, a single-phase Ag3PO4 compound formed. Hence, adjusting the Ag/Ca ratio in the starting solution allows the production of biomaterials with customized properties. In summary, this study introduces a novel synthesis method for the mono- and biphasic Ca1-xAgxHPO4·nH2O compounds brushite and silver phosphate. The preparation of these phases in a one-pot synthesis with controlled phase composition resulted in the enhancement of existing bone cement formulations by allowing better mixing of the starting ingredients.

Study on the electronic structures and optical properties of Ca-doped KH2PO4 crystal

The first-principles method has been used to investigate the impact of Ca substitution at K sites on the electrical structures and optical characteristics of KH2PO4 crystals. And we use the FNV correction approach for the finite-size system and the HSE06 hybrid functional to update the defect formation energy and fix the "band-edge" issue. The results of defect formation energy indicate that the defect CaK· is the easiest to form. Crystal properties may be more susceptible to damage. The valence band maximum (VBM) of CaK× is shifted downward and the conduction band minimum (CBM) is shifted downward. The VBM of CaK· and CaK·· is slightly shifted upward, and CBM is almost unchanged. But Ca-induced defect energy levels are responsible for bandgap reduction and conduction band bottom shift. The absorption peaks of PE-KDP and FE-KDP occur at 1.1 eV and 2.05 eV, respectively, when the electron transitions between the defect transition level and CBM. Conversely, the absorption maxima are located at 6.5 eV and 5.4 eV, correspondingly, when the electron makes a jump between the defect transition level and VBM. Stokes redshifts are 0.3 and 0.9 eV. It damages the crystal and lowers the irradiation resistance threshold by generating vibrational energy in the lattice. Avoid CaK for better KDP quality.

Effective calcium co-doping in Sm0.8Ca0.2Ba1-xCaxCo2O5+δ cathode materials for intermediate-temperature solid oxide fuel cells

High performance and durability of electrode materials are key requirements for intermediate-temperature solid oxide fuel cells (IT-SOFCs). Herein, a novel doubles perovskite oxides Sm0.8Ca0.2Ba1-xCaxCo2O5+δ (x=0.1 and 0.2; SCBCC) were prepared by A site calcium co-doping strategy. x=0.1 sample shows stabilized an orthorhombic structure with the space group Pmmm. Compared with parent SmBaCo2O5+δ, substitution of Ca for Sm and Ba effectively reduces the thermal expansion coefficient (TEC) (20.2 × 10−6 K−1 to 13.2 × 10−6 K−1). x=0.1 sample exhibits excellent chemical compatibility with CeO2-based electrolytes up to 1000 °C, the conductivity values reach 340–400 S cm−1 at 600–800 °C. The sample with x = 0.1 showed the best catalytic activity and carbon dioxide resistance. The area specific resistance and maximum power density of the x= 0.1 cathode are 0.022 Ω cm2 and 885 mW cm−2 at 800 °C. x = 0.1 double perovskite has good chemical compatibility and electrochemical properties while greatly reducing TEC, making this double perovskite a promising material for IT-SOFCs.

REE + Y distribution in Tremadocian shelly phosphorites (Toolse, Estonia): Multi-stages enrichment in shallow marine sediments during early diagenesis

Sedimentary phosphorites in Cambrian-Ordovician boundary beds in Estonia are among Europe's most extensive phosphate rock reserves, with a tonnage of approximately three billion tonnes. In addition, they are potential sources of rare earth elements and yttrium (REE + Y). The ore consists of sandstone rich in phosphatic brachiopod fragments deposited in a shallow marine peritidal environment of the Baltic Paleobasin. A detailed geochemical and mineralogical investigation was conducted on the northern part of the Toolse deposit based on three drill core cross-sections. The REE sequestration model was developed based on the correlation of the sedimentary facies of the members of the Kallavere formation. Analyses were conducted on 140 whole-rock samples and 14 discrete black shale samples. Inductively coupled plasma mass spectrometry (ICP-MS), X-ray fluorescence (XRF) and X-ray diffraction (XRD) measurements were performed for each sample. Textural analyses were conducted with field-emission scanning electron microscopy (FE-SEM), and quantitative wavelength dispersive spectrometer (WDS) analysis of major and trace elements was performed with an emission electron probe microanalyser (EPMA).The PAAS normalised REE + Y patterns were relatively homogeneous throughout the deposit except for the cerium and yttrium contents. The REE + Y contents of the phosphorites indicate a distinctive ‘bell-shaped’ pattern enriched with middle-REE (MREE) enriched. In the lower part of the deposit, the ∑REE + Y concentration is enriched up to 12-fold, compared to the average shale, reaching up to 1234 ppm. LREE enrichment is observed in these horizons, with a 9-fold peak at neodymium. In terms of absolute values, the most prevalent REEs are, in order, Ce, Y, Nd, and La, which respectively reach maximum mean values of 296 ppm, 248 ppm, 164 ppm and 135 ppm.The profiles indicate multistage uptake during transport, deposition, and early diagenesis of brachiopod detritus. The sedimentation was associated with a steep redox gradient in the porewater in a coastal environment during the beginning of marine transgression. The near-shore upwelling of oxygen-poor deeper water rich in dissolved nutrients and Mn, combined with the input of lithogenic Fe, helped create favourable conditions for REE sequestration. Positive Y anomalies indicate an initial uptake of REE + Y by hydroxyapatite through Ca substitution in an oxic environment near the sediment–water interface. The sediment burial induced the formation of carbonate fluorapatite (CAF) and a shift to the REE adsorption uptake mechanism, reinforced by the significant intercrystalline porosity of the shells. The transition to a suboxic environment below the surface layers resulted in the reductive dissolution of Mn-(oxyhydr)oxides and the release of LREE in the porewater system, resulting in an overprint of the original REE pattern to the point of inducing positive Ce anomalies. A late enrichment in MREE occurred during early diagenesis as a result of desorption of REE from the Fe-(oxyhydr)oxides and organic-rich particles under relatively anoxic conditions.

Systematic studies of the magnetocaloric properties for the La0.65Ca0.25A0.1MnO3 series (A = alkali metal and alkaline earth metals)

We present results of systematic studies of magnetocaloric effect (MCE) in a series of manganites La0.65Ca0.25A0.1MnO3 with Ca substituted by alkali metal (A = Li, Na, K, Rb, Cs) and alkaline earth metals (A = Mg, Ca, Sr, Ba), i.e. by s-block elements. At first stage we studied La1-xCaxMnO3 for × in the range 0.35–0.4 and we found that the La0.65Ca0.35MnO3 compound was the best starting composition for further fine-tuning the MCE properties by substitution for Ca with A. For each of the La0.65Ca0.25A0.1MnO3 samples an extensive characterization of the physical properties was carried out, including: structural analysis, magnetic susceptibility and magnetization vs applied magnetic field measurements, magnetic phase transition identification by Arrott plots, and finally determination of the isothermal magnetic entropy change −ΔSM. The obtained results indicate a path for searching a compromise composition, i.e. a material exhibiting a reasonable MCE performance at temperatures close to room temperature.

Microwave-aided fabrication of calcium-substituted DyMnO3 nanocomposites as prospective battery-type electrode material for supercapacitors

The Multifaceted properties of nanostructured rare earth perovskite manganite oxides have attracted much attention specifically for their applications in energy storage systems. In the present work, synthesis and physiochemical properties of calcium-substituted dysprosium perovskite manganite oxide nanocomposites and their potential applications as supercapacitors are examined. The perovskite structure and morphology of the designed nanocomposites are affirmed by the different analytical tools, including XRD, SEM, and TEM analysis. The structural analysis by XRD indicates the presence of DyMnO3 perovskite phase with additional peaks of Dy2O3 phase. The percentage of Dy2O3 is gradually reduced with higher Ca substitution, from about 16% to 7%. The Halder-Wagner method indicates an increase of the microstrain and a decrease in crystallite size with the rise of Ca substitution. From Tauc’s plot derived from DRS analysis, a slight increase in the band gap with the increase in Ca substitution is observed (2.55–2.62 eV). The surface elemental compositions and the valence states of individual elements analyzed using XPS analysis evidence the presence of Dy, Ca, Mn, and O. BET adsorption study indicates an increase in pore size, surface area, and pore volume with increasing Ca substitution concentration. When employed as a supercapacitor electrode material, Calcium-blend DyMnO3 nanocompositeexhibits battery type behavior. This material shows a higher specific capacitance (capacity) of 531 Fg−1 (319.9 Cg−1) with comparatively low charge transfer resistance and better cyclic stability. We have assembled an asymmetric supercapacitor device using our prepared sample exhibiting energy density of 36.16 Wh/kg with better cyclic stability. This work provides new insights for designing future Dy2O3 based supercapacitors.

(Ca0.95Cd0.10)Pd2Cd3, SrPd2Cd3 and (Eu0.95Cd0.10)Pd2Cd3 with YNi2Al3 type structure – crystal chemistry and magnetic hyperfine interactions

Abstract The intermetallic compounds (Ca0.95Cd0.10)Pd2Cd3, SrPd2Cd3 and (Eu0.95Cd0.10)Pd2Cd3 were synthesized from the elements in sealed niobium ampoules in an induction furnace. The polycrystalline samples were characterized through their Guinier powder patterns. The structures were refined from single crystal X-ray diffractometer data: YNi2Al3 type, P6/mmm, a = 984.61(5), c = 455.33(3) pm, wR2 = 0.0216, 376 F 2 values, 21 variables for (Ca0.95Cd0.10)Pd2Cd3, a = 998.55(8), c = 453.65(3) pm, wR2 = 0.0296, 341 F 2 values, 17 variables for SrPd2Cd3 and a = 992.57(4), c = 457.34(2) pm, wR2 = 0.0300, 384 F 2 values, 21 variables for (Eu0.95Cd0.10)Pd2Cd3. The striking crystal chemical motif in the three structures is a planar [PdCd2] Kagome-type layer. The two crystallographically independent Ca (Sr, Eu) atoms have a coordination number of 18 by 6 Pd and 12 Cd atoms. The calcium and europium compound show a small degree of Ca (Eu) substitution by Cd2 dumb-bells with 281 pm Cd–Cd in (Eu0.95Cd0.10)Pd2Cd3. Temperature dependent magnetic susceptibility measurements show Curie–Weiss behaviour (7.63(1) µB/Eu atom) for the europium compound and the onset of ferromagnetic ordering at T C = 14.9(2) K. The divalent character of europium is corroborated by 151Eu Mössbauer spectroscpy.

Study of magnetization of ferrite with Rare Earth and Ca substitutions

Study of magnetization of ferrite with Rare Earth and Ca substitutions