Zn Cr Research Articles

Magnetostriction studies on transition metal substituted cobalt ferrite

Structural, magnetic and microstructural properties of transition metal (TM) substituted cobalt ferrite Co0.9TM0.1Fe2O4 (where TM = Ti, Cr, Mn, Ni and Cu and Zn) were investigated. The present study shows marked dependence of the magnetostriction on the concentration of the substituted transition metal ions for Cobalt in CoFe2O4. The magnetic characteristics of the prepared compositions such as coercivity, anisotropy constant and saturation magnetization changed significantly on transition metal substitution. The present study shows the way to tune the anisotropy of cobalt ferrite by effective substitution of other transition metal ions for Co which subsequently affects the stress sensing performance by changing the slope of the magnetostriction curve. Apart from the magnetic properties the microstructure can also be effectively modified by substitution of other transition metal ions. Only 10% substitution of cobalt showed drastic influence on magnetostriction and slope of magnetostriction curve. The composition with 10% nickel Co0.9Ni0.1Fe2O4 exhibited maximum slope for the magnetostriction curve of −53.7 ppm/Oe, along with reasonably high magnitude of strain of 186 ppm making it a suitable for exploring stress sensing applications.

How do Cr and Zn modify cucumber plant re-establishment after grafting?

Plant grafting is a propagation technique that uses two plant individuals to optimize crop production. Although physiological traits defining the growth of grafted plants have been investigated, physiological changes caused by excessive metal nutrients or non-essential metals during the early stages of grafting have been poorly characterized. Understanding such changes would contribute to the selection of rootstocks and scions more tolerant to environmental contamination with heavy metals. Our study evaluated the responses of cucumber plants (Cucumis sativus L.) grafted onto pumpkin rootstocks (Duchesne x Cucurbita moschata Duch.); and exposed to root applications of fertigation solutions with varying concentrations of zinc (10 µM [low] or 2.44 mM [excessive]), chromium (30 µM Cr [low] or 100 µM Cr [excessive]) or both metals (30 µM Cr and 10 µM Zn). Grafted plants exposed to Cr and excess Zn increased enzyme ascorbate peroxidase activity. Plants exposed to Cr exhibited lower magnesium and manganese concentrations in leaves than both the control and Zn treatments, which were associated to low carbon assimilation. On the other hand, low Zn availability improved plant growth after grafting and superoxide dismutase in stems. We verified that the heavy metals Cr and Zn did not impair cucumber plant re-establishment immediately after grafting onto pumpkin rootstock. Our study demonstrated that grafted cucumber plants can grow in environments contaminated with Cr, but will not express their complete physiological potential.

Assessment of anthropogenic metals in shipyard sediment in the Amazon delta estuary in northern Brazil.

Shipyard activities have contributed to the release of anthropogenic metals in sediment in the Amazon delta estuary, but no studies of the issue have been carried out in northern Brazil. This study evaluated the sediment that is under the influence of shipyard activities in the Guajará Bay and in the channel of the Maguari River, in Belém, Pará (PA) state, northern Brazil. Sediment samples were collected in the vicinity of the shipyards, while samples of paint and metal fragments were collected from hulls of abandoned vessels. Metals under analysis were Cu, Zn, Pb, Ni, Cr, Ba, V, Li, Fe and Al. Mean Cu concentrations found in the sediment in two shipyards - 28.3mgkg-1 and 41.0mgkg-1 - were above the threshold effect level (TEL) for the amphipod Hyalella azteca. The highest concentrations of metals found in paint fragments from abandoned vessels were 29,588mgkg-1 Ba, 9,350mgkg-1 Zn, 1,097mgkg-1 Pb and 548mgkg-1 Cr. This fact suggests that vessel abandonment is a major source of contamination in shipyard areas. The principal component analysis (PCA) showed that most metals under study are closely related to sediment contamination in the shipyards. Geoaccumulation index and screening concentrations of inorganic contaminants for metals in freshwater ecosystems confirmed that a shipyard was contaminated by copper. Results may support further studies of contamination and application of waste management to shipyards and vessel graveyards around the world.

A comparison of two digestion methods and heavy metals determination in sediments

Abstract This study was conducted to evaluate the levels of heavy metal concentrations in sediments and also involves a comparison of two different digestion protocols. The first digestion procedure was done with a mixture of hydrochloric acid and nitric acid while the second digestion method was done using the United States Environmental Protection Agency method 3052 which comprises nitric acid, hydrofluoric acid, hydrochloric acid, and hydrogen peroxide. The sediment samples were analyzed for cadmium, copper, iron, lead, zinc, chromium, manganese, nickel (Cd, Cu, Fe, Pb, Zn Cr, Mn, and Ni) with the aid of atomic absorption spectrophotometer. Concentrations of metals ranged 0–7.0 mg/kg for Cr, 0.5–20.0 mg/kg for Cd, 10.8–112.0 mg/kg for Fe, 0.10–7.20 mg/kg for Pb, 45.69–184.96 mg/kg for Cu, 1.0–73.75 mg/kg for Zn, 1.5–19.7 mg/kg for Mn and nd −3.0 mg/kg for Ni. The order of concentrations of the metals in the samples are Cu > Fe > Zn > Cd > Mn > Pb > Cr > Ni. The second digestion method yielded higher levels of metal concentration. Comparison with theWorld Health Organization (W.H.O) standards for marine sediments showed that the average concentrations of heavy metals were within the permissible limits. Close monitoring and more publicity are further needed to discourage further pollution of the area.

Amorphous domain induced LSPR Zn–Cr–In–S solid solution with enhanced visible photocatalytic H2 production

The light absorption capacity and charge carrier separation of photocatalyst play important roles in photocatalytic hydrogen evolution activity. Metal sulfides generally show superior visible absorption; however, the charge separation efficiency is low. Formation of metal sulfide solid solution with multiple components can further enhance the light absorption; more importantly, formation of heterojunctions in nanoscale within the solid photocatalyst is an efficient approach to improve the separation efficiency of photoinduced electrons and holes. Here, the Zn1-xCrxIn2S4 solid-solution photocatalysts synthesized via a facial hydrothermal method exhibited enhanced photocatalytic hydrogen evolution activity attributed to the LSPR effect originated from amorphous domains and promoted interfacial charge transfer between amorphous domains and crystalline regions. Zn1-xCrxIn2S4 exhibited 2.2 times photocatalytic hydrogen production activity than ZnIn2S4. This work provides an avenue to construct photocatalysts with improved hydrogen evolution activity via formation of ordered-disordered domain heterojunctions combined LSPR.

Correlative an Accounts of Oil, Emulsifier and Agrochemical Pollution in Industrial Areaof Kalyan and Dombivli

Discharge of polluted water contains various toxic metals released by oil and emulsifier as well as agrochemical industries in Dombivli. A correlative account of heavy metals were studied and observed toxic metals like Cu, Ni, Cr, Pb, Fe and Zn. Oils and emulsifier and agrochemical. Oils and emulfifier were studied in details in season wise i.e. Rainy, winter and summer. In all seasonFe toxic metal was higher as compared to other metals in the influent and effluent. In winter season Fe influent was recoded more as compare to effluent while in summer season also increased Fe toxic metal andCu mg/L in Industry S3. Heavy metals were reported in all season like rainy, winter and summer. In rainy season influent and effluent were observed and found Fe and Cu more while in effluent Pb was higher and winter season Fe and Cu also higher amount were recorded effluent was reported in Pb mg/l while in summer six metal were also studied. Fe and Cu were much higher than that of rainy and winter influent and effluent.In presently investigated that the comparative studies of Oils and Surfactants (S3) and Agrochemical (S4) industries in Dombivli manufacturing industries were reported toxic metals viz. Cu, Ni, Cr, Pb, Fe and Zn more or less quantizes were observed Rainy S3 and S4 influent Fe ( 3.31 and 1.50 ) and effluent ( Fe.25 and Pb in S4. Winter season influent Fe was higher in both Industries but 51.0 Fe was reported highest pollution as compared to effluent of both industries Fe Zn Cr and Cu less amount while in Summer season Fe (15.47 and Cu 12.58) in S3 and Fe( 42.67) Cu ( 29.86)influent more concentrated then other between them and effluent S3( Fe and Zn more while in case of S4 Fe toxic metal was very high conc.

The Fe–Cr–Zn system in relation with the galvanizing process in chromium-added zinc bath

Abstract Taking into account new experimental measurements, the Fe –Zn – Cr ternary system is critically modified at 460 °C. A continuous solid solution between ζ-FeZn13 and CrZn13 compounds is shown but is shared at 460 °C by the stable CrZn17 compound containing about 2 wt.% Fe. This ternary system is assessed with the CALPHAD method using the PARROT modulus of the Thermo-Calc software. The liquid and solid solution phases are modeled with Redlich– Kister –Muggianu equations. The intermetallic compounds ζ-(Fe,Cr)Zn13 and CrZn17 are treated as stoichiometric compounds in the binary systems. The experimental Fe and Cr solubilities at various temperatures modify the shape of the liquidus curve and are satisfying for industrial applications. A set of parameters consistent with most of the available experimental data on both phase diagram and solubility measurements is obtained by optimization. A comparison with previous experimental work is also presented and a reactional model between iron substrate and Zn–Cr bath is proposed. This optimization allows to interpret the growth of intermetallic layers and the formation of dross when galvanizing in Cr-added Zn bath.

Production of Cr3+ substituted Li–Zn nanocrystalline ferrite by citrate method: Studies on structure, cation occupancy, elastic, optical and magnetic performance

The structural, elastic, optical and magnetic characteristics of Li0.4Zn0.2CrxFe2.4-xO4 (0.0 ≤ x ≤ 0.5; step 0.1) produced using a citrate precursor were studied. X-ray powder diffraction data indicate that all of the generated samples are single-phase spinel structures with no additional phases. The lattice parameter reduces from 8.355 Å to 8.333 Å when the chromium content rises. The crystallite sizes of the compositions were assessed by Scherrer's and Williamson-Hall (W–H) approaches. Infrared (IR) spectroscopy revealed two significant absorption bands generated by vibrations at the tetrahedral and octahedral sites. The elastic moduli (bulk modulus ‘B’, rigidity modulus ‘G’ and Young's modulus ‘E’) as well as the Debye temperature (θD) assessed by IR spectroscopy rise as the Cr3+ ions concentration increases. Chromium addition inhibits grain growth and enhances the mechanical strength of Li–Zn nanoferrites. Diffuse reflectance spectra (DRS) were utilized to evaluate the optical band gap (Eg) of Li–Zn–Cr nanoferrite, which was found to drop from 1.96 to 1.84 eV. The vibrating sample magnetometer (VSM) was used to perform the magnetic analysis, and various magnetic parameters were derived using the M − H curves results. Acceptable values of saturation magnetization (78.6–44.05 emu/g) and coercivity (30.87–44.65 G) were found in this system, making these nanoferrites ideal for high-density recording medium and electromagnets applications. Based on the experimental results of lattice parameters, and magnetization, a quite reasonable cation distribution was postulated for all samples. Theoretically predicted lattice parameters and magnetic moments derived from the suggested cation distribution agree with those determined empirically from XRD and VSM results, respectively. The switching field distribution curves were schemed utilizing the first derivative of magnetization data from M − H loops. The Curie temperature decreases significantly with Cr3+ substitution.

Analysis of Glasses Coated with Zn–Cr–Sn–O Thin Films by Picosecond Laser-Induced Breakdown Spectroscopy and Transmission Spectroscopy

Analysis of Glasses Coated with Zn–Cr–Sn–O Thin Films by Picosecond Laser-Induced Breakdown Spectroscopy and Transmission Spectroscopy

The effect of Cr impurity and Zn vacancy on electronic and magnetic properties of ZnSe crystal

The spin-polarized electronic energy spectra of the ZnCrSe crystal were obtained based on calculations for a supercell containing 64 atoms. First, calculation is performed with an impurity of Cr atom, replacing the Zn atom. In the second variant, the Cr impurity and the vacancy at the Zn atom site are considered simultaneously. The results obtained in the first variant are as follows. It was found that the presence of the Cr atom leads to significant changes in the electronic energy bands, showing a large difference for different spin moments. The density curves of electronic states with opposite spins show an asymmetry, the consequence of which is the existence of a nonzero magnetic moment of the supercell. It was found that in the ZnCrSe crystal electronic 3d states with spin up are present at the Fermi level, i.e. the material is a metal. For spin-down states, the material is a semiconductor in which the Fermi level is inside the band gap. The value of the direct interband gap for electronic states with spin up is equal to 1.56 eV, and the magnetic moment of the supercell is 4.00 . The results obtained by the second variant of the calculation show a significant effect of the vacancy on the zinc site on the electronic structure of the ZnCrSe crystal. The Fermi level now intersects the dispersion curves of the upper part of the valence band for both spin orientations. The magnetic moment of the supercell is 2.74 .

Covalency and Racah parameters of Fe3+ in Mn–Zn–Cr nanoferrites

This study presents the covalency and Racah parameter (B) of Fe3+ in Mn–Zn–Cr nanoferrites, which prepared by citrate–nitrate combustion method. Racah parameter was determined from the spectral data. The bands in the range of interest in optical absorbance are wide and asymmetric; a deconvolution (deconvolution to their component bands) of the experimental spectra becomes compulsory. Further, these spectra were employed to obtain Racah parameter. Racah parameter was decreased, with further Fe addition, from 540 to 441 cm-1. Also, nephelauxetic ratio (β) was decreased from 0.532 to 0.435. This denotes that the bonds of Fe3+ and its surroundings become more covalent (the covalency is increased).

Interdiffusion behaviors and mechanical properties of Zn–Cr system

Diffusion couple technique has been utilized to study the interdiffusional behaviors of Zn–Cr system. Two intermetallic compounds (Zn13Cr, Zn17Cr) have been found in the diffusion zone between 598 K and 653 K. For the existence of Zn13Cr phase, the incremental diffusion couple has been used to confirm, and the results show that the Zn13Cr phase can be determined in the present work. However, the thickness of Zn13Cr is very thinner than that of Zn17Cr, which indicate the growth of Zn13Cr is very slow. The thickness of Zn17Cr satisfied the parabolic growth law. EPMA was used to obtain the composition profiles and the interdiffusion coefficients of Zn13Cr, Zn17Cr and Zn (hcp) have been extracted by forward simulation analysis embedded in ‘Pydiffusion’ code. The mechanical properties of Zn17Cr were also determined by nanoindentation technique, and the hardness and Young's modulus of Zn17Cr is 3.01 GPa and 165.78 GPa, respectively.

An In Situ and Real-Time Plasmonic Approach of Seed/Adhesion Layers: Chromium Buffer Effect at the Zinc/Alumina Interface

The effect of additives on metal/oxide interfaces is explored in situ and in real time on evaporated films by a combination of surface science techniques, among which a very flexible optical method shows a unique ability to scrutinize the growth and wetting properties of supported clusters that involve several elements. The study focuses on Cr at the Zn/α-Al2O3(0001) interface at 300 K. A particular interest of the present interface is that Zn does not stick at all on bare alumina. The sticking and morphology of both Cr and Zn films during their growth are analyzed from sub-monolayer to multilayer thicknesses. After an initial oxidation reaction with residual OH groups, shown to be detrimental to Zn adhesion, Cr growth proceeds through the formation of high aspect ratio particles that percolate around an average thickness of 10 Å. With regard to Zn growth on a Cr deposit, two very distinct stages can be distinguished. In the sub-monolayer thickness range, Cr forms a seed layer that drastically increases the Zn sticking coefficient from 0 to nearly 1 due to a diffusion length of physisorbed Zn adatoms before desorption larger than Cr island separation; Zn clusters are anchored on the Cr seeds that they encapsulate, but their wetting behavior is dictated by the interaction with alumina. In a second stage, as soon as the Cr film percolates, it forms an adhesion layer on which Zn grows in a nearly two-dimensional mode. In all cases, Cr films are stable upon annealing. On Cr-covered alumina, the Zn desorption energy is enhanced as compared to bare surfaces, which, in line with atomistic simulations, is assigned to the formation of more favorable Cr–Al2O3 and Cr–Zn than Zn–Al2O3 bonds. Generally speaking, the ability demonstrated herein of small amounts of additives to dramatically increase the adhesion of films is of great practical interest. It shows that noncontinuous and partially oxidized films of additives, closer to realistic cases of application, can strongly enhance the sticking of films. Also, anchoring a functional film by discrete predeposited seeds can keep its properties intact.

The structure, correlated vibrations, optical parameters and metallization criterion of Mn–Zn–Cr nanoferrites

The structure, correlated vibrations, optical parameters and metallization criterion of Mn–Zn–Cr nanoferrites

Health risk assessment of heavy metals in selected Ethiopian spices

A total of 144 spice samples (ajwain, black cumin, coriander and fenugreek) were collected from three districts. For the determination of heavy metals (Cd, Cr, Cu, Pb and Zn) concentrations and human health risks, the spice samples were digested in a mixture of HNO3 and HClO4. The highest concentrations of Cr (24.85 ± 1.673 mg/kg) and Cu (32.267 ± 7.355 mg/kg) were investigated in ajwain and Zn (54.13 ± 6.122 mg/kg) in fenugreek. However, lowest concentration of Cr and Cu were detected in fenugreek; and Zn in coriander. Cd and Pb were not detected in all spice samples. A positive correlation was observed among Cr, Cu and Zn in fenugreek; Zn with Cr and Cu in black cumin and Zn with Cu in ajwain and coriander. However, negative correlation was observed Cr with Cu and Zn in ajwain and coriander; Cr with Cu in black cumin. THQ values of Cu, Zn and 75% of Cr in all spices were less than 1. About 66.7% of the HI values of the samples under study were less than 1, indicated that the consumers will not experience potential health risks from the intake of individual metals through spices consumption.

Comparative Analysis on the Phytochemical, Proximate and Mineral Composition of the Seeds and Peels of Lime

Comparative Analysis on the Phytochemical, proximate and mineral composition of the seeds and peels of lime was carried out. The phytochemical, and proximate screenings were carried out using standard methods. The mineral analysis was carried out by using Atomic Absorption Spectrophotometer. The proximate analysis revealed that the seeds contain Moisture 8.20%, Ash 12.09%,Crude fat 8.50%,Crude Protein 1.93%,Crude fibre 20.71%, and Carbohydrate 48.58% while the peels contain Moisture10.60%, Ash 15.27%, Crude fat14.67%, Crude Protein 2.30%, Crude fibre23.36% and Carbohydrate 33.80%.The phytochemical analysis revealed the presence of alkaloid, saponins, flavonoids, terpenoids, phenols, and volatile oils in both the seeds and peels of the lime. In addition, the seeds contain steroids, while the peels contain tannins, balsams and anthraquinone. The mineral analysis revealed that the seeds contains Ni(0.17mg/100g),Pb(0.01mg/100g),Mn (0.20mg/100g),Zn(0.57mg/100g)Cr(0.17mg/100g),Mg(9.02mg/100g),Ca(27.02mg/100g),Cd(0.01mg/100g), Fe(2.55mg/100g) and Cu(4.81mg/100g) while the peels contain Ni(0.15mg/100g),Pd(0.21mg/100g),Mn(0,21mg/100g),Zn(0.23mg/100g),Cr(0.13mg/100g),Mg(7.61mg/100g),Ca(100.22mg/100g),Cd(0.01mg/100g),Fe(1.67mg/100g) and Cu(0.21mg/100g).The lime seeds and peels can serve as potential sources of drugs and nutrition with the seeds having higher concentration of minerals.

Age-specific accumulation of toxic metal(loid)s in northern pike (Esox lucius) juveniles.

Northern pike specimens of 0+, 1+, and 2+ age classes were collected in June 2013 from the Vizelj channel near Belgrade (Serbia). Inductively coupled plasma optical spectrometry (ICP-OES) and atomic absorption spectrometer SpectrAA 220 were used for analyzing concentrations of As, Cr, Cd, Co, Cu, Fe, Sr, Pb, and Zn, as well as Hg in muscle, gills, and liver. Metal pollution index (MPI) was calculated. Concentrations of As, Cd, Co, and Pb were below the limit of detection. Concentrations of Cu, Hg, and Zn in muscle did not exceed the maximum allowed concentrations. The gills were tissue which was most affected by pollution. The highest concentrations of Fe in muscle, Cr and Fe in gills, and Hg, Sr, and Zn in liver were recorded in 0+ individuals, as well as Zn in gills of 2+ individuals. On contrary, the lowest concentrations were recorded for Zn in gills of 0+ individuals, Hg in gills of 1+ individuals, and Fe in muscle, Cr and Sr in gills, and Zn in liver of 2+ individuals. Regarding age classes, 2+ juveniles had the highest MPI values for all tissues. Correlations between the metal(loid) accumulation and fish condition were not significant, as well as between fish length and weight and Cu and Hg in muscle, Cu, Hg, and Sr in gills, and Cu, Cr, and Fe in liver. Results indicated that young individuals were more sensitive to pollution, but older fish showed higher overall bioaccumulation of toxic elements analyzed in this study.

Analysis of Soil Quality Status and Accumulation of Potentially Toxic Element in Food Crops Growing at Fecal Sludge Dumpsite in Ubakala, Nigeria

This study investigated the magnitude of potentially toxic element (PTE) in fecal sludge and the level of contamination of soil and food crops at Ubakala, Abia State, Nigeria. Soil samples were collected in four cardinal points at north (N), south (S), east (E) and west (W) of 1 m, 5 m, 15 m and 30 m from the edge of the fecal sludge dumpsite and standards (2 ppm, 4 ppm and 6 ppm) were prepared from 1000 ppm stock solution of the metals and used to plot the calibration curve with Atomic Absorption Spectrometer. Commonly consumed Carica papaya, Telfairia occidentalis and Manihot esculenta leaf samples were collected and analyzed to measure the concentrations of PTEs such as Cd, Zn Cr, Mn, Pb and Cu. The concentrations of Zn (12.41±0.30 mg/kg), Cd (0.07±0.00 mg/kg), Cr (4.47±0.34 mg/kg), Cu (2.12±0.03 mg/kg), Mn (8.13±0.03 mg/kg) and Pb (0.01±0.00 mg/kg) in dried fecal sludge are below the permitted limits of European Union. Concentrations of PTEs in soil and plants were Zn (13.40±1.20 to 100.80±1.40 and 1.24±0.06 to 56.02±5.02 mg/kg), Cd (0.07±0.01 to 0.92±0.02 and 0.0000±0.000 to 0.085±0.01 mg/kg), Cu (6.27±0.31 to 31.39±1.04 and 0.002±0.001 to 10.80±2.01 mg/kg), Mn (36.00±1.56 to 188.57±2.25 and 0.11±0.00 to 17.21±2.01 mg/kg), Cr (2.40±0.40 to 21.03±1.43 and 0.000±0.00 to 9.60±1.13 mg/kg) and Pb (0.09±0.02 to 0.35±0.03 and <0.00001±0.00 to 0.008±0.00 mg/kg), respectively. Zinc in soil is higher than FAO/WHO permissible limit while Cd in soil is higher than FAO/WHO limit and Dutch criteria for soil. Zinc and Cr in food crops are higher than FAO/WHO permissible limit. Strong positive relationship exist between Zn in soil and food crops (r = 0.616, p<0.05). Based on the findings, it is recommended that the fecal sludge should be treated with lime to precipitate PTE content of sludge and lowering the corresponding environmental risks.

Hybrid Accretion of Carbonaceous Chondrites by Radial Transport across the Jupiter Barrier

Abstract Understanding the origin of chondritic components and their accretion pathways is critical to unraveling the magnitude of mass transport in the protoplanetary disk, as well as the accretionary history of the terrestrial planet region and, by extension, its prebiotic inventory. Here we trace the heritage of pristine components from the relatively unaltered CV chondrite Leoville through their mass-independent Cr and mass-dependent Zn isotope compositions. Investigating these chondritic fractions in such detail reveals an onion-shell structure of chondrules, which is characterized by 54Cr- and 66Zn-poor cores surrounded by increasingly 54Cr- and 66Zn-rich igneous rims and an outer coating of fine-grained dust. This is interpreted as a progressive addition of 54Cr- and 66Zn-rich, CI-like material to the accretion region of these carbonaceous chondrites. Our findings show that the observed Cr isotopic range in chondrules from more altered CV chondrites is the result of chemical equilibration between the chondrules and matrix during secondary alteration. The 54Cr-poor nature of the cores of Leoville chondrules implies formation in the inner solar system and subsequent massive outward chondrule transport past the Jupiter barrier. At the same time, CI-like dust is transferred inward. We propose that the accreting Earth acquired CI-like dust through this mechanism within the lifetime of the disk. This radial mixing of the chondrules and matrix shows the limited capacity of Jupiter to act as an efficient barrier and maintain the proposed noncarbonaceous and carbonaceous chondrite dichotomy over time. Finally, also considering current astrophysical models, we explore both inner and outer solar system origins for the CV chondrite parent body.

Influence of Cr doping on the structural, optical, magnetic, and photoluminescence behavior of Zn0.96−xNi0.04CrxO nanostructures

Ni, Cr, co-doped ZnO nanostructures with different Cr concentrations from 0 to 4% have been synthesized using sol–gel route. Hexagonal structure of ZnO and phase purity were confirmed by X-ray diffraction (XRD) patterns. Cr doping into Zn–Ni–O could not alter the hexagonal structure. The steady decrease of crystallite size by Cr substitution revealed the proper substitution of Cr3+ instead of Zn2+ in ZnO lattice with dissimilar ionic radii. The diminishing energy gap by Cr addition is due to the s–d and p–d exchange interactions among the localized d electrons of the Cr ions. The presence of Cr in Zn–Ni–O lattice was confirmed by Fourier transform infra-red (FTIR) analysis through structural bonding. The significant modulation in photoluminescence (PL) intensity, position of different PL bands, and the increase of PL emissions by Cr doping is discussed based on electron concentration, zinc interstitial, and zinc vacancies. Room temperature ferromagnetic (RTFM) nature in the derived samples is the collective consequence of intrinsic defects and exchange interaction and not by any other magnetic or Ni/Cr oxide phases.