Different Concentrations Of Dopants Research Articles

DFT studies on structural, electronic and optical properties of aluminum nitride nanotube doped by different concentrations of boron

Nanotubes are an exceptional class of materials whose unusual properties depend on geometry and composition. In this work, we have investigated the optoelectronic properties of aluminum nitride nanotube doped with boron in concentrations of 4.2 %, 8.3 %, and 12.5 % respectively. Analysis was done by considering the structural, electronic, and optical properties of the considered nanotubes using density functional theory implemented in quantum ESPRESSO and Yambo codes. Simulations revealed that doped aluminum nitride nanotube whose nitrogen atoms were replaced turned to metallic while doped aluminum nitride nanotube whose aluminum atoms were replaced retained its semiconducting characteristics showing various band gaps with different concentrations of dopants. Optical absorption behaviors revealed that 8.3 % B-doped aluminum nitride nanotube made better utilization of visible light than others and hence can be used as a candidate for dye degradation and wastewater treatment, solar cell, LED, and LASER. In the end, all the doped nanotubes were found to be worthy for various fields of science and technology.

Synthesis and thermoluminescence characteristics of beta irradiated nanocrystalline calcium aluminate doped with lanthanum oxides

This study investigated the thermoluminescence (TL) characteristics of calcium, a nano-phosphor doped with a rare earth element (lanthanum, La). Six different concentrations of dopants were prepared by the sol-gel method. The XRD data displayed that the particle size was 52.48 nm. The surface morphology was examined by SEM analysis. The highest TL response of the nano-phosphor CaAl2O4 was found with a dopant of 0.1 % La, which has the most intense TL peak. The Computerized Glow Curve Deconvolution (CGCD) and Variable Heating Rate (VHR) methods were carried out for trap-level analyses and activation energy determination. The deconvolution of the glow curves displayed thirteen superimposed TL glow peaks located between 362 and 717 K. The TL response of CaAl2O4:0.1 % La nano-phosphor showed linearity in the beta dose range from 2.2 Gy up to 330 Gy for all the deconvoluted glow peaks. The minimum detectable dose of the prepared samples is 284 μGy. Other parameters, such as the sensitivity and reproducibility of the prepared samples, were determined. It is concluded that CaAl2O4 with a dopant of 0.1 % La is a good material for dosimetry applications.

Synthesis and photoluminescence characterisation of Ca2La2O5:Eu3+, a novel red-emitting phosphor: a comprehensive study

ABSTRACT A novel low-melting-temperature chemical flux method was used to synthesise a Ca2La2O5 lattice doped with Eu3+ ions in the range of 0.5-2.5 mol-%. The phosphors were characterised by powder X-ray diffraction (PXRD), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy, particle size distribution, photoluminescence (PL), and Fourier transform infrared spectroscopy, respectively. The PXRD pattern revealed the hexagonal crystal structure with the space group P63/m. The microstrain (ϵ) was found to not vary with different concentrations of dopant and the negative means compression in the lattice. Particles of varying sizes and irregular shapes were observed from the SEM micrographs. The EDAX mapping revealed that all the constituent elements were found to be in appropriate ratios. Interestingly, the Ca2La2O5:xEu3+ (x = 0.5-2.5 mol-%) phosphor samples were excited at 590 nm, showing a Stokes-shifted red-PL with significant intensities at 615 and 627 nm. Unconventionally, when the phosphor is excited at 590 nm, the Eu3+ ion-characteristic luminescence owing to 5D0→7FJ (J = 0, 1, 2, 3, 4) transitions are manifested. Another remarkable observation is that the PL at 627 nm corresponding to 5D0→7F3 transition was much stronger than the 615 nm emission of Eu3+ corresponding to 5D0→7F3 transition, indicating high colour purity among the available red-emitting phosphors.

Morphological evolution and transition at nanoscale in BSTO ceramic materials

Considerable efforts have been devoted since the past three decades for the development of low cost ferroelectric and clean energy storage multifunctional materials. Modification in design and production of a low cost material with well proven process provides pathway for high energy density dielectric energy storage. We studied fluorine doped a commercially well-established material system barium strontium titanate with two different concentrations of dopants and studied the morphological transition and its effect on properties. It was observed that sample with higher concentration transitioned much faster into glassy state, followed by growth of fibers which turned into a self-arranged bird nest type shape. The sample with lower concentration changed slowly into glassy state and only few fibers were farmed. Dielectric was highly dependent on processing methods and shows variation with crystallinity of material, temperature, and cooling conditions during processing. In the higher concentration range, we observed nano-scale interface breakdown very similar to that of solid-liquid interface breakdown during crystal growth.

Sonochemical synthesis of Ag doped zinc sulfide /iron oxide nanocomposites for photocatalytic and magnetic separation applications

The influx of numerous organic contaminants and heavy metals into freshwater sources has serious effects on the aquatic environment and has made life very difficult. Synthesized photocatalysts have demonstrated considerable promise in the degradation of organic pollutants, such as dyes from various sources. This research presents the sonochemical synthesis of Ag doped zinc sulfide/iron oxide nanocomposites as magnetically separable photocatalysts with bifunctional applications. To determine the effect of the weight percentage of dopant on photocatalytic activity, Ag doped zinc sulfide/iron oxide nanocomposites were prepared at different concentrations of dopant, including 2.5, 5, and 10 wt%. Zinc sulfide/iron oxide nanocomposites with and without Ag dopant were employed as photocatalysts for degrading rhodamine B (RhB) as a color pollutant under visible and UV light. In the present study, the photocatalysts were characterized by using x-ray diffraction (XRD), field emission scanning electron microscope (FE-SEM), (energy dispersive x-ray spectroscopy (EDS), Brunauer-Emmet-Teller (BET), vibrating sample magnetometer (VSM), fourier transform infrared spectra (FTIR), photoluminescence (PL) spectrophotometry and ultraviolet–visible (UV–Vis) spectrophotometer to survey their structural, morphological, magnetic and optical features. Besides, the Mott-Schottky analysis was utilized to derive the carrier concentrations (ND), flat band potentials of the samples. The results show that doping of Ag in the zinc sulfide/iron oxide nanocomposite led to extended visible light absorption. In addition, approximately 96% of RhB was degraded by 5 wt% Ag doped zinc sulfide/iron oxide nanocomposite after 4hr of visible light irradiation. Moreover, 10 wt% Ag doped zinc sulfide/iron oxide nanocomposite demonstrated a considerable specific surface area (147.7 m2 g−1), which indicates a noteworthy adsorption capacity of 2.74 m g−1. Also, it was demonstrated that the zinc sulfide/iron oxide photocatalyst exhibited a strong magnetic capacity which was revealed by a saturation magnetization (Ms) of 58.22 emu/g, a remanent magnetization (Mr) of 1.4emu/g and a coercivity (Hc) of 11.62 Oe. Eventually, the photocatalytic mechanism of Ag doped zinc sulfide/iron oxide was thoroughly discussed. Therefore, to benefit from the potential of Ag dopants in the preparation of nanocomposites for wastewater treatment while maximizing the photocatalytic efficiency, a thorough study of their effect on the structural and optical properties of photocatalysts is required.

Transition metal doping and co-doping effect on electronic and magnetic properties of zb-ScN

The ab-initio study of electronic and magnetic properties and Curie temperature of transition metal (TM) doped ScN diluted magnetic semiconductor (DMS) are calculated using generalized gradient approximation (GGA) implemented in AKAI-KKR-CPA package. The total and partial density of states (DOS) of pure zinc blend ScN as well as TM doped compounds are plotted for different concentrations of dopants. Our results shows that the Sc substituted by TM materials induces a half-metallic character in the system for different concentrations except for Sc1−xNixN (x > 8%). Also, We found that the Sc1−xVxN, Sc1−xCrxN, Sc1−xMnxN compounds are stable in ferromagnetic states, while Sc1−xCoxN and Sc1−xNixN compounds prefer antiferromagnetic phase. In addition, the minority-spin bands depicted a half-metallic ferromagnetic (HMF) gap and half-metallic (HM) gap. To improve this latest result, doping ScN with double impurities (Co, Ni) is also investigated. As a result, our results show a stable antiferromagnetic state in the majority of cases. The mechanism of exchange interaction is also discussed for all doped systems and the high curie temperature are found for most concentrations. The present results suggest TM doped ScN as potential candidate for spintronic devices.

Effect of NaBr on the Structural, Thermal and Mechanical Properties of HPMC:NaBr Composite Films

The hydroxypropyl methylcellulose (HPMC):sodium bromide (NaBr) composite films were prepared using different concentrations by solution casting method. The crystalline percentage of the pure HPMC was reduced from 74% to 60% upon the incorporation of 0.7 wt.% of NaBr salt, which suggests that the NaBr salt disrupted the host polymer crystalline phase. The two-phase microstructure in the morphological images reflects the phase separation at different concentrations of dopant. The functional studies revealed the considerable variation of intensity and the shift of peaks due to the action of NaBr in the host polymer matrix. The HPMC showed a large increase in the glass transition temperature (Tg) from 65 ºC to 86 ºC and simultaneously reduction in the weight percent loss was observed. The mechanical analysis revealed that the added dopant has a significant effect on the mechanical properties of HPMC.

Study of the Effect of Y2O3 Doping on the Resistance to Radiation Damage of CeO2 Microparticles under Irradiation with Heavy Xe22+ Ions

This paper presents the results of a study on the influence of Y2O3 doping on the resistance to radiation damage and an assessment of structural changes associated with the accumulation of radiation defects in CeO2 microparticles under irradiation with heavy Xe22+ ions. The relevance of this study consists of the prospects for the use of CeO2 microparticles as materials and candidates of inert matrices of nuclear fuel. A method of solid-phase synthesis was applied to obtain microparticles with different concentrations of dopant. It included grinding of CeO2 and Y2O3 microparticles followed by thermal sintering at 1100 °C in an oxygen-containing medium to produce highly ordered microparticles. During the study of the structural characteristics of the synthesized microparticles, it was found that increasing the dopant concentration from 0.05 mol.% to 0.15 mol.% leads to an increase in the crystallinity degree as well as a decrease in dislocation density. According to the results of the assessment of the resistance of microparticles to radiation damage, it was found that an increase in the dopant concentration leads to a decrease in swelling and structural distortion by more than 2.5–3 times, which indicates an increase in the radiation resistance.

Assessing the structural and interaction behaviour of Pr@Gd2O3 nanoparticles with biological entities

The current work focuses on accessing the potential aptitude of the rare-earth-doped Gadolinium oxide (Gd2O3) nanoparticles as a function of dopant concentrations with biological entities in aqueous media. A series of Pr@Gd2O3 NPs were synthesized by fast and economically viable microwave-assisted methodology. Various high end techniques such as high resolution transmission electron microscopy (HRTEM), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), vibrating sample magnetometric studies, thermal gravimetric analysis and scanning electron microscopy (SEM), were employed to characterize the prepared particles. The optical, magnetic and thermal properties of Pr-doped Gd2O3 (doping percentage = 5, 10 and 15%) were scrutinized in relationship with their optical band gap, spectroscopic properties, defect states and thermal stability. In order to access the effect of different concentrations of dopant on the biocompatibility of Gd2O3, in vitro biocompatibility studies on the bacterial and fungal stains have been performed. These variables were on the basis of dopant amount (5, 10 and 15% of Pr) and initial concentration (10, 50, 100 ppm). The outcomes of in-vitro blood compatibility assay showed the biocompatible aptitude of effect of Pr@Gd2O3 NPs as a function of initial concentration ranging from 10, 50, 100 ppm. The relative effect on the chromosomal aberrations in root meristems of A. cepa shown the reduction of 20%, 23%, 8% in mitotic index (MI), correlative mitotic index (CMI) and index of phase (PI) values with increase in Pr doping amount. The high biocompatibility was observed for 10 ppm of Pr@Gd2O3 NPs. Collectively; the outcomes of the present study exemplify the various properties of Pr@Gd2O3 NPs with potential biomedical efficacies.

Machine learning identification of experimental conditions for the synthesis of single-phase white phosphors

<h2>Summary</h2> Single-phase white phosphors for solid-state lighting are commonly designed using different dopants responsible for emissions in different spectral regions. However, the phenomena of energy transfer and concentration quenching often prevent any clear prediction of the accurate experimental conditions to be selected, leading to a time-consuming trial-and-error discovery process. In this article, a high-throughput experimental approach equipped with machine learning (ML) enabling an efficient identification of the experimental conditions for designing a white phosphor is demonstrated. Li₂BaSiO₄:Eu,Ce was selected to illustrate this strategy. A total of 88 samples were prepared from the initial synthesis of eight compounds with different concentrations of dopants followed by a post-treatment under a gradient of temperature. The decision tree model identified the experimental conditions for designing a white emission. The analysis of the experimental conditions to obtain other colors of emission, which were also identified by ML, enabled rationalization of the different mechanisms of energy transfer between dopants.

Electrical and magnetic properties of nanostructured Ni doped CeO2 for optoelectronic applications

Employing hydrothermal technique, undoped and nickel doped cerium oxide nanoparticles (Ni doped CeO2 NPs) are synthesized with different concentration of dopant (5 M%, 10 M% and 15 M%). Prepared samples are subjected to Powder X-ray diffraction (PXRD), Scanning electron microscopy (SEM), Energy dispersive X-ray spectroscopy (EDX), High resolution transmission electron microscopy (HRTEM) with selected area electron diffraction (SAED), Raman spectroscopy, Fourier transform infrared spectroscopy (FTIR), Ultraviolet–visible spectroscopy (UV–vis), Photoluminescence spectroscopy (PL), Vibrational sample magnetometry (VSM), Dielectric and electrical conductivity studies. Formation of CeO2 NPs and Ni doped CeO2 NPs is confirmed by PXRD and EDX. The crystallite size of the samples, determined from powder XRD using Williamson-Hall (W–H) plot, diminishes with increased Ni doping. The lattice parameter variation indicates an initial lattice contraction when the doping is less and a lattice expansion with enhanced Ni doping. These variations in crystallite size and lattice parameter could be due to the replacement of Ce ions by Ni ions in the CeO2 lattice. SEM and HRTEM images show that the morphology of the NPs formed is nearly spherical. The UV–vis spectroscopic studies indicated that bandgap energy of Ni doped CeO2 NPs widens as the Ni dopant concentration is increased. Increase of oxygen vacancy (VO) with increase in Ni concentration is designated by Raman spectra. The PL studies show that the nanoparticles of CeO2 and Ni doped CeO2 exhibit luminescence in the violet-blue-green wavelengths region (400 nm–500 nm). The decrease in emission intensity with increase of Ni concentration is indicative to increase of oxygen vacancies with increase in Ni content which act as non-radiative centers. VSM studies show that all the samples exhibit paramagnetism. The saturation magnetization and the retentivity of the samples increase as the Ni dopant concentration increases. All the samples display frequency dependent dielectric properties. With increase in the concentration of Ni dopant and frequency, a reduction in the values of dielectric constant and dielectric loss and an improvement in the electrical conductivity were observed for all the samples.

High Power Diode-Pumped Erbium Laser Emitting at Near 1.5 μm

Solid-state lasers emitting in the 1.5–1.6 μm spectral range are very promising for eye-safe laser range finding, ophthalmology, fiber-optic communication systems, and optical location. The aim of this work is the investigation of spectrosposcopic and laser properties of gain medium based on borate crystal for abovementioned lasers.Spectroscopic and laser properties of Er,Yb:YAl3(BO3)4 crystals with different concentrations of dopants were investigated. Polarized absorption and emission cross-section spectra were determined. The ytterbium- erbium energy transfer efficiency was estimated. The maximal energy transfer efficiency up to 97 % was obtained for Er(4 at.%),Yb(11 at.%):YAl3(BO3)4 crystal.The laser operation of heavily doped crystals with erbium concentration up to 4 аt.% (2.2^1020 cm^3) was realized. By using of Er(2 at.%),Yb(11 at.%):YAl3(BO3)4 crystal a maximal continuous- wave (CW) output power of 1.6 W was obtained at 1522 nm with slope efficiency of 32 %. By using of Er(4 at.%),Yb(11 at.%):YAl3(BO3)4 crystal a maximal peak output power up to 2.2 W with slope efficiency of 40 % was realized in quasi-continuous-wave regime of operation. The spatial profile of the output beam was close to TEM00 mode with M2 &lt; 1.2 during all laser experiments.Based on the obtained results, it can be concluded that Er,Yb:YAl3(BO3)4 crystals are promising active media for lasers emitting in the spectral range of 1.5-1.6 pm for the usage in laser rangefinder and laser- induced breakdown spectroscopy systems, and LIDARs.

Effect of the bivalent dopant ionic radius, electronegativity and concentration on the physical properties of the sol–gel-derived ZnO thin films

This study deals with the influence of the concentration and ionic radius of the bivalent dopant on the structural, morphological and optical properties of the sol–gel-derived ZnO thin films. For that, different concentrations of dopants with different radii (Ni2+, Cu2, Fe2+) have been chosen to synthesize many ZnO thin films. The X-ray diffraction confirms that all the obtained films exhibit a pure hexagonal wurtzite structure. Meanwhile, it appears that both the preferential film orientation and the crystal quality are strongly affected when varying the ionic radius or the concentration of dopant. We note also that the lattice parameters decrease when the electronegativity of the dopant increases. This behavior has been explained at the light of a simple schematic model, based on the electrostatic forces involved in chemical bonding. The Scherer formula reveals that the average size of the crystallites is ranged between 20 and 35 nm. On the other hand, as confirmed by the SEM analysis, all the deposited films present a compact, uniform and nanocrystalline morphology. Nonetheless, the optical analysis indicates that the Ni- and Fe-doped films are highly transparent (greater than 90%) in the visible region, while the Cu-doped ones exhibit the lowest transmission (about 76%). Additionally, a blue shift of the bandgap is noticed when doping with Ni or Fe, whereas the doping with Cu induces a red shift.

(V, Ti) co-doping effect on electronic and magnetic properties of zb-AlAs

The ab initio study of electronic, magnetic properties and Curie temperature of AlAs doped by single and double impurities is investigated using LDA–KKR–CPA method. It is shown that the Al substituted by V and/or Ti induces a half-metallic character and ferromagnetism in the system for different concentrations except co-doping by x[Formula: see text]=[Formula: see text]y[Formula: see text]=[Formula: see text]0.035. The stability of magnetism between the ferromagnetic and DLM states as well as the mechanism of exchange interaction are discussed. The density of states are plotted in the energy diagram for different concentrations of dopants. The co-doping with (V, Ti) increases Curie temperature in AlAs with respect to single substituant. The finding of this work confirms that the new compounds have a great potential for spintronic devices.

Simulation of the ion beam‐plasma interaction processes for point‐like ions in doped DT plasmas

The purpose of this work is to study the interaction between an ion beam and a doped deuterium‐tritium (DT) plasma in a fast ignition nuclear fusion context. In order to analyze the influence of the dopants in the interaction process, we present a physical model to carry out spatial‐temporal simulations of the stopping of an ion beam interacting with a doped plasma target, the plasma heating processes, and the formation of the ignition regions. We perform a set of numerical experiments where different concentrations of dopants are added to a fully ionized DT plasma. These simulations allow us to characterize the increase in the stopping power and the maximum temperatures achieved with the presence of impurities, as well as the reduction of the heated and ignition regions. This reduction in the ignition region indicates difficulties for the formation of an efficient hot spot when there are dopants in the DT plasma.

The effect of external applied fields on the third order nonlinear susceptibility and two-photon absorption cross-section of E5CN7@Fe3O4-CNT

The third order nonlinear optical properties and two-photon absorption(TPA) cross-section of nematic liquid crystals (NLCs) (E5CN7) doped with Fe3O4 nanoparticles, single wall carbon nanotubes (SWCNTs) and Fe3O4-CNTs were investigated at 632.8 nm. For this aim, the low power single beam was used in Z-scan technique. The study was performed with two different concentrations of dopant with and without the electric field (15 Volt) and magnetic field (0.5 Tesla). The functionalization of SWCNTs with Fe3O4 diminishes the CNT aggregation while the third order nonlinear susceptibility and TPA cross-section are increased. The results show that the best concentration and dopant in E5CN7 without any applying fields is 1% Fe3O4-CNT. After applying electric and magnetic fields and compare the results, the E5CN7@1% Fe3O4-CNT under electric field exhibits the largest nonlinear responses among all the samples. The direction of external fields with respect to the director axisn→ and then the type of initial alignment are crucial factors for changing the nonlinearity parameters. Furthermore, these results show that E5CN7@1% Fe3O4-CNT may be the promising candidate for the magneto-optical devices.

Facile Electrolytic Synthesis of ϒ- Manganese Dioxide From Manganese Sulphate Solutions In The Presence of Betaine

Manganese dioxides (MnO2), which are of great use in industrial sector, now draw huge attention for purposes pertaining to storage of energy and fuel cells. Effect of different concentrations of dopant on the synthesis, morphology and electrochemical performances of MnO2 has been studied. In this context, betaine as impurity or dopant in the electrolytic solution was observed to improved the cell voltage, current efficiency and energy consumption during deposition of electrolytic manganese dioxide (EMD). It was observed that better electrodeposition performance was achieved when concentration of betaine was varied from 0 to 50 ppm. There was a sharp increase in current efficiency from 92.5 to 96 % and low cell voltage from 2.458 to 2.446 V and less energy consumption from 1.639 to 1.518 KWhKg-1 Finally, the results of the characterization of MnO2 obtained shows to be nano-size particles, which ensures high surface area of the materials and also one of the important requirement for high discharge capacity batteries.

Chalcogens doped BaTiO3 for visible light photocatalytic hydrogen production from water splitting.

The pristine BaTiO3 has been experimentally confirmed to catalyze hydrogen production from water splitting, but the reaction cannot be driven by the visible light because of the wide energy band gap of BaTiO3. To understand the feasibility of the reaction driven by the visible light of the strongest part of the solar energy, we have investigated the effect of different concentrations of oxygen group element dopants on the electronic and optical properties of BaTiO3 by using first-principles density functional theory calculations with meta-GGA + MBJ potential. The formation energy of each doped structure is calculated to examine the feasibility of synthesis in energy. The energy band gaps and the energy positions of conduction and valence bands are calculated and the results reveal that all the structures except the one that doped with 5 at% Te satisfy the conditions of water splitting although the energy band gaps of the doped BaTiO3 decrease obviously. The partial charge distributions of conduct band maximum and valence band minimum are used to demonstrate the electron-hole separation. The absorption coefficients are calculated for all the considered structures. The results demonstrate that the doped chalcogens can significantly enhance the absorption in visible light range, which implies that the doped BaTiO3 are promising to catalyze the hydrogen production from water splitting driven by solar energy.

Electrochemical, UV–Vis, and microscopical characteristics of sol–gel CeO2:V2O5 thin film

Cerium dioxide (CeO2) and cerium dioxide doped with vanadium pentoxide (CeO2:V2O5) were synthesized from sol–gel precursors and deposited by spin coating on a conductive glass substrate (FTO). The films with different concentration of dopant and number of deposited layers were studied throughout cyclic voltammetry (CV), chronoamperometry/chronocoulometry, atomic force microscopy (AFM), scanning electron microscopy (SEM), and UV–Vis spectroscopy. The best value of charge density of 18.9 mC cm−2 was obtained for CeO2 doped with 15 mol% of V2O5 film. The chemical diffusion coefficient of lithium ions into CeO2 was 1.73 × 10−12 and CeO2:V2O5 15 mol% 6.75 × 10−13 cm2 s−1. This film presented 79% of transparency in UV–Vis and 5% color change under ± 1.3 V of applied potentials. Structural analyses revealed its homogeneous surface and the root mean-squared roughness (RMS) value of 9.42 nm. Based on the obtained results, CeO2 doped with 15 mol% V2O5 film is a promising thin coating for the use in electrochromic devices as a passive counter-electrode.

Fabrication of Calcium Doped PlSZT Ceramics using High Planetary Mill Method

Ca-doped modified Lead Lanthanum Strontium Zirconium Titanate (PLSZT) ceramic, was synthesized with different concentrations of dopant in order to enhance the properties of PZT. Calcium carbonate, CaCO3 have been used as a source of Ca dopant in the preparation of PCLSZT using high planetary ball mill, palletized and sintered at 1200 °C for 3 hours. The uses of high planetary milling benefit in shorten the time for powder preparation where the calcination was not required. The concentration of CaCO3 was varied from 0.01, 0.03, 0.05 and 0.10 mol% and their effects on phase formation, surface morphology, density and porosity have been studied using X-ray diffraction (XRD) and Scanning electron microscopy (SEM). XRD results showed that all Ca-doped PLSZT samples present a tetragonal phase. Whereas SEM results showed that the grain size of the samples was increased with increasing calcium concentration. In addition, the density was observed to be decreased with increasing amount of Ca concentrations.