Polycrystalline samples of M-type hexaferrite with BaZnxZrxFe12–2xO19 (x = 0.1–0.7) as chemical composition were synthesized successfully using solid state reaction technique. The structural, ...microstructural and magnetic properties of these samples were investigated. Rietveld analysis (goodness-of-fit ≈1.06–1.22) demonstrates the phase purity of the samples in the entire composition range. The `c/a′ ratio is < 3.98, for all samples implying that they are M-type hexaferrites. The XRD results also show a simultaneous decrease in crystallite size (149–69 nm) and an increase in cell volume (699.119–711.006 Å3) with increasing dopant concentration. FESEM micrographs reveal that the a) average grain size varies within 0.61–0.79 µm and b) sample porosity decreases with increasing concentration of Zn2+- Zr4+ dopants. EDX data reveals the presence of all the elements and Ba:Fe ratio ≈ 1:12. M-H studies reveal that a) Ms increases from 61.45 emu/g (at x = 0) to 72.87 emu/g (at x = 0.1) and decreases afterwards to 61.45 emu/g (at x = 0.7) and b) Hc decreases continuously from 4118 Oe (at x = 0.0) to 319 Oe (at x = 0.7). The excellent magnetic properties of these hexaferrite samples make them useful in magnetic data storage devices, devices for microwave absorption and in spintronic devices.
•Rietveld analysis established the phase purity in BaZnxZrxFe12–2xO19 (x=0.1-0.7) samples.•A decrease in crystallite size and an increase in cell volume is observed with increasing Zn-Zr concentration.•FESEM micrographs reveal that the sample porosity decreases with increasing Zn-Zr concentration.•EDX data reveals the presence of both the majority as well as minority elements .•Ms increases from 61.45 emu/g (at x = 0) to 72.87 emu/g (at x = 0.1) and decreases afterwards.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Abstract
In this report, the effect of rare-earth (RE
3+
) ion substitution on structural, microstructural, and electrical properties in barium bismuth titanate (BaBi
4
Ti
4
O
15
) (BBTO) Aurivillius ...ceramics has been investigated. The Rietveld refinements on X-ray diffraction (XRD) patterns confirm that all the samples have an orthorhombic crystal system with A2
1
am space group. Meanwhile, temperature dependent synchrotron XRD patterns reveal that the existence of dual phase in higher temperature region. The randomly oriented plate-like grains are experimentally strived to confirm the distinctive feature of bismuth layered Aurivillius ceramics. The broad band dielectric spectroscopic investigation signifies a shifting of ferroelectric phase transition (T
m
) towards low temperature region with a decrease of the RE
3+
-ionic radii in BBTO ceramics. The origin of diffuse ferroelectric phase transitions followed by stabilization of the relaxor ferroelectric nature at high frequency region is explained using suitable standard models. The temperature dependent ac and dc conductivity results indicate the presence of double ionized oxygen vacancies in BBTO ceramics, whereas the dominance of single ionized oxygen vacancies is observed in RE-substituted BBTO ceramics. The room temperature polarization vs. electric field (P–E) hysteresis loops are shown to be well-shaped symmetric for BBTO ceramics, whereas slim asymmetric ferroelectric characteristics developed at RE-substituted BBTO ceramics.
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IZUM, KILJ, NUK, PILJ, PNG, SAZU, UL, UM, UPUK
Green and sustainable energy production through renewable sources is an enormously exciting field of research. Herein, we report an A-site lanthanum doped oxygen excess ruthenate (predominantly Ru
5+
...-ions) double perovskite system, CaLaScRuO
6+
δ
(CLSR), as an excellent photocatalyst for water splitting. The well characterized polycrystalline compound shows canted antiferromagnetic (AFM) behavior due to the existence of disordered Ru-ions at the B-site. Based on density functional theory +
U
(Hubbard
U
) calculations, we have estimated various magnetic exchange interactions and found that the ground state is antiferromagnetic in nature which is in perfect agreement with our experimental results. Detailed analysis of the electronic structure further reveals that the present system belongs to the family of charge transfer semiconductors with an energy gap of ∼0.45 eV. Finally, the material is found to proficiently work for the oxygen evolution reaction (OER)
via
visible-light driven water splitting at neutral pH in an ecofriendly manner.
CaLaScRuO
6+
δ
is a new disordered system acting as active photocatalyst for oxygen evolution reaction in presence of visible light. Theoretical study predicts the most stable magnetic orientation correlating the experimentally observed behavior.
Polycrystalline samples of Ba
0.96
Ca
0.04
Ti
0.91
Fe
0.09
O
3
were prepared using a conventional solid state reaction route with different Fe starting precursors (Fe
2
O
3
, Fe
3
O
4
). The Rietveld ...refined XRD data confirmed the phase purity and tetragonal crystal structure of both the samples. The average grain size measured using SEM was 0.40 μm in both the samples. XPS analysis confirmed the presence of only Fe
2+
and both Fe
2+
/Fe
3+
in Fe
2
O
3
and Fe
3
O
4
doped BCT samples. The
P
r
and
M
r
values have been measured to be 1.34 μC cm
−2
, 2.88 μC cm
−2
and 0.0015 emu g
−1
and 0.135 emu g
−1
in Fe
2
O
3
and Fe
3
O
4
doped BCT samples, respectively. The Fe
3
O
4
doped samples exhibit much better M-E coupling ( 22%) as compared to Fe
2
O
3
( 7%) doped BCT samples. The results obtained hence suggest that Fe
3
O
4
doping in BCT is better suited for multiferroic applications.
Polycrystalline samples of Ba
0.96
Ca
0.04
Ti
0.91
Fe
0.09
O
3
were prepared using a conventional solid state reaction route with different Fe starting precursors (Fe
2
O
3
, Fe
3
O
4
). A significant difference in the magnetic and ferroelectric properties was observed.
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IJS, KILJ, NUK, UL, UM, UPUK
Ni1-xZnxO nanoparticles were synthesized by wet-chemical route. XRD characterization of these samples indicated that Zn doping in NiO neither induces structural phase transformation nor any secondary ...phase. Rietveld refinement of XRD data indicated that the lattice parameter of NiO increases with increasing of Zn doping concentration. TEM analysis confirms the reduction of agglomeration and shape transformation from irregular to almost spherical shape up on Zn doping in NiO. Raman study combined with photoluminescence study suggested that these materials could be useful for optical applications. Magnetic characterization of Ni1-xZnxO samples indicates that all samples show weak ferromagnetism at room temperature with the persistence of unsaturation behavior even up to very high magnetic field. Our study indicated that the synthesized samples could be useful for UV emission device, magnetic random access memory and data storage applications.
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•Zn doping in NiO not only prevents aggregatation but also induces shape transformation from irregular to spherical shape.•Luminescence property of NiO is enhanced up on Zn doping.•The observation of low remanence magnetization in the Ni1−xZnxO nanoparticles indicated the samples are magnetically clean materials and could be useful for data storage applications.•Existence of memory effect in the Ni1−xZnxO nanoparticles is confirmed from the negative slope of the Arrott plot.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
•The Mn moments order ferromagnetically in the ab-plane (intra-layer).•Along the c-direction, the Mn moments align anti-parallel to each other (inter layer).•A weak antiferro-ferri magentic ...trnaistion was observed at 25 K.•At 241 K a ferrimagnetic to paramagnetic transition was observed.
Magnetic properties of intermetallic MnFe0.25Sb through magnetization and heat capacity measurements with the support of powder XRD patterns and electronic structure calculations are presented in this paper. Fe atoms occupy the vacant 2d sites in MnSb and as a result, the a-parameter increases and the c-parameter decreases. Both the magnetic ordering temperature and the saturation magnetization are smaller than those of MnSb. An A-type antiferromagnetic behaviour, where the Mn moments order ferromagnetically in the ab-plane (intra-layer) and the interlayer (along the c-direction) exchange is antiferromagnetic, was observed below 25 K. Specific heat data too revealed a small change in entropy at 28 K, consistent with the observations from the magnetization data. Furthermore, at 241 K a ferrimagnetic to paramagnetic transition was observed. Electronic structure calculations showed that MnFe0.25Sb stabilized in an A-type antiferromagnetic (AFM) like ground state. In this state, the exchange interactions between the moments of (i) Mn atoms along the c direction and (ii) Mn and Fe atoms are antiferromagnetic and is ferromagnetic between the moments of Mn atoms in the ab-plane. The competition between these interactions leads to magnetic frustration, which also emphasizes the near-degeneracy of different magnetic states.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
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•Annealed specimens had higher transition temperatures.•The magnetic saturation values were also better for the annealed specimens.•Magnetic field induced strain values showed an ...improvement as compared to the previous measurements on ribbons.•Dependence of magnetic saturation on the orientation has also been presented.
A large magnetic field induced strain is indicative of an ideal ferromagnetic shape memory alloy. To achieve high strain values melt-spun ribbons of NiMnGa based Heusler alloy were prepared and annealed at different temperatures over different time periods. Thermal analysis was done to obtain the transformation temperatures of the annealed ribbons. Besides the magnetic measurements, magnetic field induced strains were measured using strain gauges and strain indicator. The dependence of magnetic moment on the angle of alignment of the sample surface with respect to the field direction has been reported. The transformation temperatures were closer to the room temperature in all the ribbons with an incremental dependence on the annealing temperature and annealing time. The martensitic transformation temperatures obtained from the thermomagnetic curves were almost similar to those obtained from thermal analysis. There was an improvement in the saturation magnetization values after annealing whereas the Curie temperature was roughly similar for all the specimens. Presence of precipitates along the grain boundaries had no significant role to play in determining the properties. The annealed ribbons showed higher magnetic field induced strain (MFIS) than the as-spun ribbons; ribbon prepared at 1300 RPM and subsequently annealed at 900 °C for 5 h showed the highest value of MFIS ~0.15%. From the texture analysis, fraction of 〈001〉 oriented grains decreased and that of 〈110〉 increased with the progression of angle of alignment from 0° to 90°. Hence, the moment was higher when the angle of alignment was 90° in the annealed specimens.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
An attempt has been made to bridge between the influence of surface modification at nanoscale and the biomedical applicability of multifunctional nanocomposite. Fe3O4 synthesized via solvothermal ...route has been made nanocomposite with Polyethylene glycol (PEG) and Amine functionalized Multiwall Carbon nanotube (MWCNT). Formation of Fe3O4 phase has been confirmed by X-ray diffraction (XRD). Functionalization of MWCNT with PEG and Amine has been recognized by Fourier transform infrared (FTIR) Spectra. Thermogravimetric analysis (TGA) discerned the adhesion of functional groups onto MWCNT and also the loading of functionalized MWCNT in the nanocomposite. Besides the visible evidence of interaction of spherical Fe3O4 onto walls of MWCNT provided by High-resolution transmission electron microscopy (HRTEM), there are other inferences led by the influence of this functionalized group. Crystallographic information from Rietveld analysis of the XRD pattern infers the impact of functionalized MWCNT on cation distribution in the Fe3O4 spinel structure. Vibrating sample magnetometer (VSM) studies revealed near superparamagnetic nature of as-synthesized samples, with 17% rise and 19% fall in the Coercivity of PEG-o-MWCNT/Fe3O4 and Amine-o-MWCNT/Fe3O4 than bare Fe3O4 respectively. A comparison of the Specific absorption rate suggested that under an oscillating magnetic field, nanocomposites are capable as an agent of heat generation as bare Fe3O4, even better at the higher field amplitude for tuning with magnetic anisotropy.
•Oxygen in PEG-o-MWCNT, reduces discrepancy in surface oxygen coordination of Fe3O4 yielding almost ideal inverse structure.•σ-donor in Amine-o-MWCNT leads to high spin state of d5-orbitals of Fe3+ ion, so that octahedral site preference energy becomes higher.•In PEG-o-MWCNT/Fe3O4 HC increases, since π-donation contracts the CFSE.•In Amine-o-MWCNT/Fe3O4 HC decreases, since σ-donation expands the CFSE.•With increase in HA, heating efficiency (SAR) of nanocomposite increases at faster rate than bare Fe3O4.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Ni
0.93-x
Zn
0.07
Li
x
O (
x
= 0, 0.01, 0.03 and 0.05) and Ni
0.92
Zn
0.07
Fe
0.01
O samples were prepared following a simple cost effective wet chemical route. XRD characterization along with ...Rietveld refinement indicated that the samples crystallize in the fcc phase of host NiO without forming any impurity phases. The crystallite size of the parent Ni
0.93
Zn
0.07
O sample is reduced either by Li or Fe co-doping. Photoluminescence study revealed that the Li co-doping into Ni
0.93
Zn
0.07
O led to the suppression of UV emission intensity along with the shifting of emission towards the blue region. The magnetic study revealed that the all samples exhibit weak ferromagnetism in the antiferromagnetic background of NiO. Arrott plot with negative slope in Zn-doped and (Li, Zn) co-doped NiO samples illustrates the first-order magnetic transition. This in contrast with the observation of (Fe, Zn) co-doped NiO sample where the second-order magnetic transition with positive slope in Arrott plot is appeared. All the samples show robust exchange bias and coercivity features at room temperature. Our study indicated that these samples could be useful for multifunctional device applications.
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DOBA, EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, IZUM, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, SIK, UILJ, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
Synthesis of Ba0.96Ca0.04Ti1–3x/4FexO3 (0.06 ≤ x ≤ 0.15) samples has been reported using solid state reaction technique. XRD data established that the samples up to x = 0.08 are phase pure and ...possess tetragonal crystal structure. The structural data also confirmed the existence of additional hexagonal Fe doped BaCaTiO3 and Fe2O3 phases beyond x = 0.08 and insignificant variation in the lattice parameters of various phases with x. FESEM data revealed a slight increase in average grain size with increasing x. The dielectric data reveals the presence of diffuse and downshift of ferroelectric transition (above room temperature) in all the samples. The presence of Fe in multiple oxidation states was confirmed using XPS analysis. Magnetic ordering (except x = 0.06 sample) and ferroelectricity driven by charge ordering was observed in all the samples. The best ferroelectric, magnetic behaviour and M-E coupling strength was exhibited by x = 0.12 sample with Pr and Mr values being 2.88 µC/cm2, 3.4 × 10−2 emu/g, respectively. The M-E coupling strength was also observed to be highest in this sample (≈ 31.25%). Multiple magnetic transitions were observed in the high temperature M-T data of x = 0.12 and x = 0.15 samples, implying the presence of magnetic inhomogeneity.
•Ba0.96Ca0.04Ti1-3x/4FexO3 (0.06 ≤ x ≤ 0.15) samples were successfully prepared using solid state reaction technique.•The XRD data revealed the phase purity of samples upto x = 0.08.•The segregation of hexagonal Fe doped BaCaTiO3 and Fe2O3 phases was observed for x>0.08.•The presence of multivalent Fe oxidation states was confirmed using XPS analysis.•M-E coupling was observed in all the Fe doped BCT samples with maximum at x = 0.12 ≈ 31.25%.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
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