Effect Of Ca Doping Research Articles

Study on Ca-doping effects and structural stability in Bi2Sr2-xCaxCuO6+δ (0 ≤ x ≤ 1.2) compounds by Rietveld refinement and high-pressure Raman spectroscopy

The lattice distortion induced by element doping is regarded as an effective approach to improve the superconductivity of Bi-based superconductors. In this study, a series of Bi2Sr2-xCaxCuO6+δ (x = 0, 0.2, 0.4, 0.6, 0.8, 1.0 and 1.2) ceramic samples are prepared by Pechini sol-gel method. The Ca-doping effects, structural stability and superconductivity of Bi-2201 phase are studied by electron microscopy, high-pressure Raman spectroscopy, the standard four-probe technique, X-ray diffraction and Rietveld refinements. Results indicate that all samples are constituted by Bi-2201 main phase and Ca8.56Sr5.44Bi16O38 impurity. It can be determined that Ca atoms have entered Bi-2201 orthorhombic lattice and preferentially occupied the Sr-sites. When Ca atoms are introduced and high-pressure is exerted, the Bi-2201 lattice can present a relatively high structural stability. Meanwhile, the correlations between doping amount x, Cu–O–Cu bond angle (θ), carrier concentration of CuO2 planes and superconducting onset transition temperature (Tc,onset) are discussed particularly. It should be noted that the Bi-2201 lattice has the largest θ, the highest carrier concentration and the highest Tc,onset value of 84.98 K when x = 0.8.

Effect of Ca doping on Li ion conductivity of Ge and Ta doped garnet LLZO

The series Li6.55+xGe0.05La3-xCaxZr1.75Ta0.25O12 (x = 0, 0.05, 0.10, 0.15, 0.20) was prepared by conventional solid state reaction method with the sintering temperature of 1050 °C for 7.30 h by substituting Ca at the La site to increase the Li ion conductivity. The synergistic effects of Ca incorporation on Li6.55Ge0.05La3Zr1.75Ta0.25O12 were studied using various structural and electrochemical analyses. X-ray diffraction, scanning electron microscopy, and Impedance analysis were used to determine the crystal structure, morphology, and AC conductivity of the prepared ceramic samples, respectively. The highest conductivity of 9.95 x 10−4 S/cm was obtained for a 0.05 Ca ceramic sample with minimum activation energy of 0.23 eV. The DC polarization measurements confirmed the dominance of ionic conduction in 0.05 Ca ceramic. The results obtained make the 0.05 Ca ceramic sample a promising candidate as solid electrolytes for all solid state Li-ion batteries (ASSLIBs).

Competing effects of Ca doping on the phase transition and related properties in (Ba1–xCax)(Ti0.95Sn0.05)O3 ceramics

Competing effects of Ca doping on the phase transition and related properties in (Ba1–xCax)(Ti0.95Sn0.05)O3 ceramics

Resistive switching behavior in ZnO:Ca thin films deposited by a pulsed laser deposition technique

Calcium-doped ZnO (CZO) nanopowders were synthesized using the sol–gel method. The structural characteristics were investigated by X-ray diffraction (XRD) and the analysis reveals that our samples are crystalized in a wurtzite hexagonal structure. The morphological properties and the chemical composition of the nanoparticles were studied by transmission electron microscopy (TEM), scanning electron microscopy (SEM), and energy-dispersive X-ray spectroscopy (EDX). The obtained powders are stoichiometric with crystallites in a nanometric scale aggregated in micrometric particles. Then, pulsed laser deposition (PLD) technique was used to grow Ca-doped ZnO thin films with different doping concentrations (1, 3, and 5%), on p-type Si substrates. The Ca doping effect on the electrical properties of the CZO films was investigated by current–voltage characteristics. A resistive switching (RS) effect was observed in the ITO/ZnO:Ca/Au structures. The RS behavior is dependent on the Ca doping concentration. The charge transport mechanisms of the devices were studied. In the positive bias voltage region, the transport is dominated by Ohmic and space-charge limited conduction mechanisms under low and high electric fields, respectively.

Effect of Ca doping on the arbitrary canting of magnetic exchange interactions in La1-xCaxMnO3 nanoparticles

La1-xCaxMnO3 nanoparticles (x = 0.1, 0.2, 0.3) (LCMO NPs) were synthesized using the coprecipitation method. The prepared samples were investigated using x-ray diffraction (XRD), which confirmed the single-phase structure. The nanoparticle’s crystallite size was determined using Debye–Scherrer’s formula. Scanning electron microscopy showed that the size of the nanoparticles was between 33 nm and 55 nm. Energy-dispersive x-ray spectroscopy (EDX) was used to determine the elemental composition of samples. The four-probe method was used to measure the temperature-dependent electrical resistivity. Magnetic properties, such as hysteresis loop, magnetoresistance, and magnetization versus temperature, were measured using a vibrating sample magnetometer. The study of magnetization versus applied magnetic field M(H) showed that, at 77 K, all the loops exhibit ferromagnetism. DC magnetization versus temperature at a 70-Oe-applied field for all samples showed a paramagnetic-ferromagnetic phase transition. A decrease in Curie temperature Tc after increasing the concentration of x was observed. The real and imaginary parts of temperature-dependent ac magnetic susceptibility were measured and revealed a transition from the ferromagnetic to the paramagnetic phase at a particular temperature Tc, with DC magnetization behavior.

La1-xCaxMnO3 NTC ceramics for low temperature thermistors with high stability

A new perovskite-structured NTC ceramic with high stability for low temperature thermistors, the La1-xCaxMnO3 (0 ≤ x ≤ 0.25) system, was originally explored by the conventional solid-state reaction. XRD analysis confirmed that the sintered La1-xCaxMnO3 ceramics were composed of a hexagonal perovskite when x ≤ 0.05 and an orthorhombic perovskite when x ≥ 0.1 with a tiny amount of Mn3O4 phase. SEM images showed that the grain size and the segregated Mn3O4 both decreased with Ca content increasing. The effects of Ca doping on the electrical properties were also investigated. With Ca increasing, the resistivity ρ decreased slowly within a narrow range (ρ25 °C: 1.52–4.13 Ω•cm), while the B25/50 value decreased sharply (from 1559 K to 385 K). Such combination of parameters enables it a potential candidate for NTC thermistors applied to low temperature. The thermal stability was also obviously improved by Ca doping, reducing △R/R0 from 10.91% (x = 0) to 0.25% (x = 0.20) after aging at 125 °C for 1000 h.

Green conversion of excess sludge to N-Ca self-doping sustainable carbon quantum dots with remarkable fluorescence enhancement and residual heavy metal reduction

“Waste” is “Wealth”. Recovering valuable materials from excess sludge (ES) is trending as an efficient strategy that synergizes waste management and resource recovery. Targeting the inherent composition characteristics of ES, this study aimed to explore resource recovery strategies that can exert its unique advantages. ES from paper mill was unprecedently selected as the carbon precursor, and ES-derived carbon quantum dots (ESCQDs) were successfully synthesized via a facile and one-pot hydrothermal reaction without pretreatments, catalysts or any additives. Notably, its fluorescence quantum yield (QY) and mass recovery rate were as high as 28.472 % and 2.86 %, respectively, which were at a high level among biomass-derived CQDs. N-Ca was successfully co-doped into ESCQDs without any nitrogen or calcium amendment, which has been reported rarely. The effect of Ca doping on the enhancement of QY of CQDs was revealed, thereby revealing the natural advantageous properties of ES from paper mill in the synthesis of high fluorescent Ca-N co-doped CQDs. Furthermore, the effect of the preparing ESCQDs on the environmental risks control of ES were also investigated. This resource recovery process efficiently removed residual heavy metals from ES and significantly reduced and controlled the environmental risk of heavy metals in ES, and the synthetic ESCQDs had low toxicity and excellent biocompatibility. This study proposed a green alternative that combines the recovery of value-added products from ES with heavy metal control, provided more in-depth understanding for the formation mechanism of CQDs, and revealed structural strategies for the preparation of high fluorescent CQDs.

Borosilicate glass alteration in vapor phase and aqueous medium

A Na-alumino-borosilicate glass and its Ca-doped counterpart were altered in vapor phase (98% relative humidity) and aqueous medium at 90 °C. Both the alteration media were enriched in 17O. Characterization of the altered samples pointed out some differences between glass alteration in aqueous medium and vapor phase in terms of the alteration kinetics, the effect of Ca-doping on glass chemical durability, the behavior of elements in the gel layer, and the structure of the gel layer. Some of the key results are the recondensation of boron in the gel layer formed in the vapor phase and the utility of Rotation Echo DOuble Resonance Nuclear Magnetic Resonance spectroscopy to qualitatively distinguish between signals from the pristine glass and hydrated gel layer within a sample that was not altered to the core. The results gave rise to inferences about glass alteration mechanisms in both the alteration media and the differences between them.

Ca doping effect on the performance of La1−xCaxNiO3/CeO2-derived dual function materials for CO2 capture and hydrogenation to methane

CO2 valorization in form of synthetic natural gas is a convenient way to store large amounts of intermittent energy produced from renewable sources for long periods of time. Here reported research addresses the development of novel dual function materials (DFMs) for the utilization of CO2 from simulated post-combustion effluent by cyclic adsorption and in-situ methanation. These DFMs, obtained after the controlled reduction of 20% La1−xCaxNiO3/CeO2-type precursors (with x = 0–0.5), are widely characterized before and after catalytic tests. XRD diffractograms, H2-TPD experiments and STEM-EDS images denote that Ca-doping shows low influence on materials composition, slight detrimental effect on textural properties and no influence on Ni, La and Ce distribution. Meanwhile, the concentration of Ca-based species increases as long as La3+ substitution by Ca2+ increases, which leads to a progressively promotion of medium and, especially, strong basic sites concentration (CO2-TPD). As a result, the 20% La0.5Ca0.5NiO3/CeO2-derived DFM almost doubles (188.8 µmol g−1) the CH4 production of the 20% LaNiO3/CeO2-derived DFM (96.5 µmol g−1) at high temperatures. Indeed, this novel DFM enhances the methanation capacity of the conventional 15% Ni-15% CaO/Al2O3 DFM (143.0 µmol CH4 g−1), with higher stability during long-term experiments and adaptability under variable feed compositions, which further support the applicability of these novel DFMs. Thus, Ca doping emerges as an effective way of tailoring CO2 adsorption and in-situ hydrogenation to CH4 efficiency of 20% LaNiO3/CeO2-derived DFMs.

Structure, electric transport, and magneto-transport properties of metallic double-chain based Pr[formula omitted]Ca[formula omitted]Ba2Cu4O8 with low Ca substitution

In this study, we showed the crystal structure, electric resistivity, Seebeck and Hall coefficients, magneto-resistance, and magnetic susceptibility of Pr1−xCaxBa2Cu4O8 (x= 0.0, 0.02, and 0.05) are all relevant for our understanding of physical properties along CuO double chains. The lattice parameters of Ca substituted PrBa2Cu4O8 remained almost invariant up to x= 0.05. Contrary to the Ca doping effect in the PrBa2Cu3O7−δ system, the significant increases in the Seebeck and Hall coefficients due to the Ca substitution indicate a decrease in the carrier number. The significant magneto-resistance effect in the parent sample (16% at 10 K) was significantly reduced down to 5% in the x= 0.05 composition. On the basis of the two types of carrier models, we discussed the influence of Ca substitution on the electrical transport and magneto-transport properties.

Effect of Ca Doping on the Microstructure and Mechanical Properties of Magnesium Aluminate Spinel

Effect of Ca Doping on the Microstructure and Mechanical Properties of Magnesium Aluminate Spinel

Promotional effect of Ca doping on Bi2Fe4O9 as peroxymonosulfate activator for gatifloxacin removal

A series of Ca-doped bismuth ferrite was prepared at various %w/w of Ca via a facile hydrothermal method to obtain Bi2XCa2(1-X)Fe4O9 (denoted as BFOCa-X, where X = 1, 0.95, 0.90, 0.80, 0.50). The BFOCa-X catalysts were characterized, and the results showed that they consist of pure phase BFO with nanosheet-like morphology. The as-prepared BFOCa-X catalysts were used as peroxymonosulfate (PMS) activator for gatifloxacin (GAT) removal. It was found that the catalytic activity decreased in the following order: BFOCa-0.8 (90.2% GAT removal efficiency in 45 min, kapp = 0.084 min−1)>BFOCa-0.95 > BFOCa-0.9 > BFOCa-0.5 > BFO indicating that BFOCa-0.8 has the optimized active sites for catalysis. The Ca dopant contributed to the increased oxygen vacancies and surface hydroxyl groups, promoting the catalytic PMS activation process. The kapp value increased gradually with increasing catalyst loading and PMS dosage while pH 9 presented the highest GAT removal rate. The GAT degradation rate was inhibited by PO43ˉ, humic acid and NH4+ but promoted in the presence of Clˉ, NO3ˉ and HCO3ˉ. It was also found that the GAT can undergo several degradation pathways in the catalytic PMS system, which eventually mineralized into innocuous compounds. The dominant reactive oxygen species (ROS) were identified using chemical scavengers, revealing that SO4•ˉ, 1O2 and •OH contributed significantly to GAT degradation. Based on the XPS study, PMS was activated by the Fe2+/Fe3+ redox cycling and oxygen vacancies to produce SO4•ˉ/•OH and 1O2, respectively. Overall, the BFOCa-0.8 also showed excellent reusability up to at least 4 cycles with low Bi and Fe leaching (<7 and 62 μg L−1, respectively), indicating that it has promising potential for application as PMS activator for antibiotics removal.

Effect of Ca Doping on Magnetic Properties of Lanthanum Chromate LaCrO3

Effect of Ca Doping on Magnetic Properties of Lanthanum Chromate LaCrO3

Development of a half-metallic ferrimagnetic state in Lu[formula omitted]NiIrO[formula omitted] via hole-doping

Ferrimagnetic (FiM) materials have attracted much attention owing to their dynamic magnetization capacity, which has potential applications in spintronics. Herein, electronic and magnetic properties of Lu2NiIrO6 double perovskite oxide are investigated under the effect of Ca-doping at Lu site using ab-initio calculations. It is established that the undoped system is FiM Mott-insulator with an energy band gap of 0.20 eV, which is attributed to a strong antiferromagnetic (AFM) interactions between high energy half-filled Ni+23d8 (eg2↑ eg0↓) and low energy partially filled Ir+45d5 (t2g3↑ t2g2↓) ions. The structural and dynamical stability of the doped system is confirmed by computing the formation energy and phonon dispersion bands, respectively. The analysis of magnetic ordering by comparing FiM, ferromagnetic, and AFM energies of the Ca-doped Lu2NiIrO6 system reveals that FiM ordering is the ground state alike the undoped case. A half-metallic behavior is obtained for Ca-doped system, because the admixture of Ir 5d orbitals in the spin majority channel is primarily responsible for conductivity. Moreover, a substantial enhancement in the magnetic moment on one of the Ir ions is also observed due to the reduction of Ir-O hybridization.

Understanding the combined effect of Ca doping and phosphate coating on Ni-rich LiNi0.91Co0.06Mn0.03O2 cathode material for Li-ion batteries

Ni-rich cathode materials are one of the promising candidate due to their high discharge capacity and better rate capability for Li-ion batteries. However, these materials retain a large amount of residual lithium compounds (LiOH and Li2CO3) on the surface which are responsible for the gas generation during battery operations. In addition, structural instability of Ni-rich oxides leads to irreversible phase transition during the cycling process. To address these problems, a promising technique has been adopted to reduce the residual lithium and also enhance the structure stability of these materials. In this work, LiNi0.91Co0.06Mn0.03O2 has co-doped and coated with CaHPO4 by a solid-state process. This strategy has successfully achieved the Ca2+ doping and phosphate coating on the surface, thus stabilizing the host structure and reducing the amounts of residual lithium. Among the various amount of CaHPO4, the 0.5 mol% (CaP-0.5) sample exhibits the best electrochemical properties. The CaP-0.5 delivers a discharge capacity of 210.2 mAh g−1 (0.1 C) and capacity retention of 77.9% after 80 cycles at 0.5C and rate capability of 75.5% at 3C. Thus, we can conclude that, the improvements in cyclability and rate performance of CaP-0.5 are mainly due to the enhanced chemical and structural stability.

High Power Factor and Thermoelectric Figure of Merit in Sb2Si2Te6 through Synergetic Effect of Ca Doping

High Power Factor and Thermoelectric Figure of Merit in Sb₂Si₂Te₆ through Synergetic Effect of Ca Doping

Effect of Calcium Doping Using Aqueous Phase Reforming of Glycerol over Sonochemically Synthesized Nickel-Based Supported ZrO2 Catalyst

The aqueous phase reforming (APR) of glycerol was studied using sonochemically synthesized 10%Ni-x%Ca/ZrO2 catalysts (where x = 0, 0.5, 3, and 5) for the production of value-added liquid products. The APR reaction was performed in a batch reactor under the following conditions: 20 bar, 230 °C 450 rpm, and 1 h of reaction time. The synthesized catalysts were characterized using XRD, FESEM, BET, and H2-TPR to observe the effect of Ca doping on the physio-chemical properties of the catalysts. The results revealed that, at higher Ca loading, the catalysts experienced serious particles’ agglomeration, which resulted in a larger particles’ size, smaller surface area, and smaller pore volume owing to uneven distribution of the particles. The characterization results of the catalysts confirmed that the Us catalysts have a slightly higher surface area, pore volume, and pore size, as well as highly reducible and fine crystalline structure, compared with WI catalysts. The catalytic performance of the catalysts shows that 1,3-propanediol (1,3-PDO) and 1,2-propanediol (1,2-PDO) were the two main liquid products produced from this reaction. The highest selectivity of 1,3-PDO (23.84%) was obtained over the 10%Ni/ZrO2 catalyst, while the highest selectivity of 1,2-PDO (25.87%) was obtained over the 10%Ni-5%Ca/ZrO2 catalyst.

Effect of Ca doping on photovoltaic effect of BiFeO3

Effect of Ca doping on photovoltaic effect of BiFeO3

Effects of Ca doping on the crystallization kinetics of GeTe

Doping is an effective way to improve the performance of conventional phase-change materials. We introduced an alkaline element calcium (Ca) in GeTe films and studied their crystallization kinetics by using flash DSC. It was found that a small amount of Ca doping (4.0 at. %) can significantly enhance the thermal stability, but the maximum crystal growth rate does not decrease significantly. Moreover, no any Ca-related crystalline phase and Ca-related chemical bond can be found in Ca-doped GeTe, implying that Ca atoms are in free state in GeTe matrix.

Studying the Effect of Ca Doping and Li3PO4 Coating on Ni-Rich LiNi0.91Co0.06Mn0.03O2 Ncm Cathode Material for Lithium Ion Batteries

Both environmental and energy concerns have shifted our dependence from fossil fuels to develop advanced renewable energy resources and energy storage devices for the portable electronic devices and electric vehicles [1]. Improvements in energy density, cost and safety are prime requirement for enabling the long range electrical vehicles [1]. Lithium ion batteries got huge attention due to their high discharge capacity and excellent capacity retention. Currently, Li[NixCoyMnz]O2 (NCM) is a promising candidate which has shown great potential in hybrid vehicles and electric vehicles. NCM is consists on three transition metals; Ni provides high discharge capacity but suffers from thermal instability, Co offers better electronic conductivity but at high cost and Mn provides stabilizes the host structure and enhance cycling at the cost of low capacity. Ni-rich LiNi1-x-yCoxMnyO2 (x + y ≤ 0.4 ) cathode materials have garnered a lot of attention for EV applications due to their higher discharge capacity and power density [2]. However, the major problem of Ni-rich NCM is their structural instability which leads to phase transition from layered to spinel to rock-salt structure. Another major issue is the cation mixing; unstable Ni3+ reduce to Ni2+ (0.69 Å) spontaneously, which migrates from transition metal slab (TM-slab) to Lithium slab (Li+; 0.76 Å) due to similarity in their ionic sizes. The dissolution of transition metal ions in the electrolyte (LiPF6-based) is another critical problem [3].To solve these problems, we exploit CaHPO4 to provide enhance structural stability and protects the surface from side reaction with electrolyte as well. The precursor Ni0.91Co0.06Mn0.03(OH)2 and LiOH were mixed in 1:1.05 ratio and pre-heated at 500 °C - 5 h followed by sintering at 740 °C - 15 h. The modified samples were prepared by mixing Ni0.91Co0.06Mn0.03(OH)2 and LiOH (1:1.05) along with CaHPO4 (0, 0.5, 1, 3 and 5 wt%). The samples were investigated with XRD and SEM. Later on, the electrodes were fabricated and their electrochemical properties were measured.XRD results confirm the Ca doping by shifting of (003) diffraction peak to the low angle and additional peaks were detected which belongs to the Li3PO4 phase. SEM results show that the particles have sustained their spherical morphology which means that calcium is doped successfully. The 0.5 wt% sample resulted in improved electrochemical studies as compared to the rest. The enhanced properties are originated from optimized amount of doping and coating which results in stabilizing the host structure and protecting the surface.Ca2+ enhanced the structural stability while Li3PO4 acts as Li-reactive coating to suppress the reaction between the active material and electrolyte. The modified sample offers superior cyclability and enhanced electrochemical performance.