Effect Of Nd Substitution Research Articles

Effect of Nd substitution on electronic, thermoelectric, and optical response of WO3

The properties of Nd-doped WO3 thin films are studied to assess their suitability for photovoltaic and optoelectronic applications. The simulations on pristine and Nd-doped WO3 were performed using Tran Blaha modified Becke-Johnson approximation to explore the various properties, whereas the spin coating technique was employed to synthesize thin films. X-ray diffraction analysis revealed the crystalline cubic structure in all synthesized thin films. The morphology contains uniform rod-like features and the width of these were enhanced in doped composition. The projected density of states demonstrated the major prominent contributions of W-d in conduction and O-p in the valence band while Nd-f orbital plays a major contribution in doped compositions. Thermoelectric parameters were found to change significantly with Nd incorporation in WO3. The highest refractive index and real epsilon values were recorded at the higher energy regimes approximately 2.96 and 8.61, respectively, for compositions containing maximum dopant content. The optical conductivity and absorption coefficient showed an enhanced trend in doped composition which is considered favourable for improved optoelectronic and photovoltaic applications. The experimental band gap of WO3 was calculated as 2.03 eV and found to decrease with increment of Nd doping concentration.

Fundamental properties of melt-spun stoichiometric Y2Fe14B alloy and the advantages of Nd substitution

Here we investigate the effects of wheel speed and heat treatment on the melt-spun ternary Y2Fe14B alloy, aiming to clarify its structure, phase precipitation and magnetic properties. For directly quenched alloys, the optimum magnetic properties can be achieved when the wheel speed is within a relatively wide range of 30–40 m/s. The Y2Fe14B alloy prepared at 36 m/s shows the highest coercivity of 149 kA/m and remanence of 0.88 T with the maximum energy product (BH)max of 6.8 MGOe due to the single hard magnetic phase structure. For the amorphous ribbons prepared at 50 m/s, when the annealing temperature increases from 773 to 1073 K, the α-Fe phase precipitates first accompanied by the appearance of Y2Fe14B phase and a small quantity of Fe-B phase. The magnetic properties of annealed samples are much lower than those of the optimized as-spun alloys. The effects of Nd substitution for Y on the structure, magnetic properties and thermal stability of (Y1-xNdx)2Fe14B (x = 0–1) alloys have been systematically investigated. The Hcj and (BH)max exhibit almost linear increase with the increasing Nd substitution. Relatively low temperature coefficients can be obtained in the Nd substituted alloys. The current results are important for exploring high performance and low cost Y­based rare earth permanent magnets with improved thermal stability.

Influence of Nd substitution on the structural, magnetic and electrical properties of NiZnCo ferrites

Samples of Ni0.6Zn0.3Co0.1NdxFe2-xO4 (0.00 ≤ x ≤ 0.10) ferrites were synthesized by the sol-gel auto-combustion method and microwave sintering technology. The effects of Nd substitution on the crystal structure, magnetic, and electrical properties have been investigated. The XRD results showed that the main phase of sintered samples was a standard spinel structure. When x > 0.02, the second phase appeared in the sintered samples, which led to the phenomenon that the lattice constant of the sample increased and then decreased. Overall, the saturation magnetization of the samples showed a downward trend, and the value of coercivity increased with the amount of substitution. In terms of electrical performance, the dielectric constant of the samples showed an overall increasing trend with the amount of substitution after a sharp drop in the low frequency band and tended to be stable in the high frequency band. At x = 0.02, the ferrite sample exhibited the lowest dielectric constant (ε', 41.63), the highest dc resistivity (ρ, 4.973 × 106 Ω∙m), relatively small coercivity (Hc, 20.878 Oe) and relatively high saturation magnetization (Ms, 79.214 emu/g).

Effect of Nd Substitution for Mischmetal on Magnetic Properties in (MM,Nd)-Fe-B Ribbons

Mischmetal-based permanent magnets of (MM,Nd)SUB12/SUBFeSUB82/SUBBSUB6/SUB were prepared by melt-spinning method via varying the relative content of mischmetal and Nd. The coercivity is low, and the squareness of hysteresis loop is poor in MMSUB12/SUBFeSUB82/SUBBSUB6/SUB ribbons. The x-ray diffraction pattern, maximum of δm value as well as the temperature dependence of magnetization indicates that the partial substitution of Nd for MM could improve the crystallinity in the mischmetal-based magnets, and both the coercivity and squareness of hysteresis loop increase with Nd substitution for mischmetal. The increase of squareness should be partially attributed to the improvement in the crystallinity of R₂FeSUB14/SUBB crystal phase. For more than 4 at.% Nd substitution the coercivity is not less than that in corresponding (Ce,Nd)-based magnets, and the coercivity of 7.81 kOe and the maximum energy product of 15.41 MGOe were obtained in MMSUB8/SUBNd₄FeSUB82/SUBBSUB6/SUB ribbons. These investigations show that it is reasonable to use the low cost mischmetal to prepare the resource-saving rare-earth magnets, and that optimizing the addition amount of Nd is necessary to improve the crystallinity and enhance the magnetic properties.

Effect of Nd-substitution on the structural, magnetic and magnetocaloric properties of La0.67-xNdxCa0.13Ba0.2MnO3 manganites

The effects of the substitution of La3+ by smaller rare-earth ion Nd3+ on the structural, magnetic and magnetocaloric properties of La0.67-xNdxCa0.13Ba0.2MnO3 (x = 0.02, 0.06, 0.1) manganites prepared by solid state sintering technology have been investigated. X-ray diffraction analysis shows that the x = 0.02 sample crystallizes in the rhombohedral structure with R3¯c space group symmetry and the x = 0.06, 0.1 samples belong to the orthorhombic structure with Ibmm space group. The Rietveld refinements for all samples were carried out to investigate on the crystal structures of the samples. Thermomagnetic measurements indicate that all the samples exhibit a magnetic transition from ferromagnetic to paramagnetic phase with increasing temperature. The Curie temperature TC systematically decreases from 308 K to 280 K with the accumulation of Nd concentration. Critical analysis demonstrates that the estimated critical exponents β, γ and δ are between the theoretically predicted values for 3D-Ising and mean-field theory models for all samples. The magnetic entropy change has been calculated from the isothermal magnetization measurements as a function of the applied magnetic field at various temperatures near TC. The maximum magnetic entropy change -ΔSmax under an applied magnetic field of 1.6 T was found to be 3.06, 2.92 and 2.48 J kg−1 K−1 respectively for x = 0.02, 0.06 and 0.1 samples. This indicates that these manganites are remarkably potential functional materials working as magnetic refrigerants near room temperature.

Enhanced formation of 2:14:1 phase in La-based rare earth-iron-boron permanent magnetic alloys by Nd substitution

Aiming at promoting the formation of hard magnetic 2:14:1 phase in La-Fe-B alloys, the effects of Nd substitution on the melt-spun nanocrystalline (La1-xNdx)yFe94-yB6 alloys (x = 0–0.5; y = 12–16) have been investigated. No hard magnetic phase was formed in the (La1-xNdx)16Fe78B6 alloys with x < 0.2. A soft magnetic phase (La,Nd)2Fe23B3 with Curie temperature of 649 K was observed in the x = 0.2 alloy and it disappeared as x increased to 0.3. 30% and above Nd substitution can dramatically enhance the formation of 2:14:1 phase and the magnetic properties of La-based permanent magnets. Three different alloy systems (y = 16, 14 and 12) show similar behavior of magnetic properties dependences on Nd substitution. (La0.7Nd0.3)16Fe78B6 alloy with mean grain size 10–20 nm exhibits high remanent magnetization, maximum energy product and intrinsic coercivity up to 0.71 T, 10.0 MGOe and 562 kA/m, respectively, indicating it is possible to achieve excellent magnetic properties in La-based rare earth permanent magnets. The present work provides a good understanding on the fundamental magnetism of La-based magnets and the potential to develop low cost rare earth permanent magnets.

Effect of Nd Substitution on Properties of Multiferroic Bismuth Ferrite Synthesized by Sol-Gel Auto-combustion Method

In this work, pure and Nd-doped bismuth ferrite nanocrystals with the general formula of Bi1−x Nd x FeO3 (x = 0, 0.05, 0.1, 0.15, 0.2) were synthesized via the sol-gel auto-combustion method at two different calcination temperatures (550 and 650∘C). Phase analysis and investigating structural, thermal, and magnetic properties and measuring the size of nanoparticles have been done by using X-ray diffraction (XRD), transmission electron microscopy (TEM), thermogravimetric and differential thermal analysis (TG/DTA), and vibrating sample magnetometry (VSM). For undoped BiFeO3 (BFO), increasing calcination temperature will increase the average size of nanocrystals. On the other hand, the average size of nanoparticles is decreased by increasing the concentration of neodymium in the structure of BFO. By entering neodymium to the structure of bismuth ferrite at the calcination temperature of 550∘C, the ferromagnetic properties decline. However, at 650∘C, ferromagnetic properties are improved which is due to a fall in the number of Fe2+ ions. In this case, by decreasing the Fe2+ ions, remanent and saturation magnetization increase.

Phase precipitation behavior of rapidly quenched ternary La–Fe–B alloy and the effects of Nd substitution

To understand the structure and phase precipitation behavior of the ternary La–Fe–B alloy, the effects of wheel speed and heat treatment on the melt spun La2Fe14B alloy were investigated. The results show that the hard magnetic La2Fe14B (2:14:1) phase is difficult to obtain in the ternary alloy. The α-Fe and La phases mainly precipitated as spun ribbons prepared at relatively low wheel speeds, and a more amorphous phase formed at higher wheel speeds. With the annealing temperature increasing from 400 °C to 500 °C and 800 °C, the α-Fe and La phases also gradually precipitated from the amorphous matrix. A liquid La-rich phase and α-Fe phase could coexist in the alloy at high temperature. However, the substitution of Nd for La can greatly enhance the formation of a hard 2:14:1 phase. The effects of Nd substitution on the structure and phase precipitation during annealing for the (La1−xNdx)2Fe14B (x = 0.1. 0.2, 0.3 and 0.4) alloys have been also investigated. The present results are important for exploring high-performance low-cost La-based Nd–Fe–B magnets.

Magnetocaloric effect in Gd1−xNdxZn2

The magnetization of Gd1-xNdxZn2(0<x⩽1) was measured to study the effect of Nd substitution in GdZn2 with a Curie temperature of 85K and a spin-reorientation transition temperature of 58K on the magnetocaloric effect. The Nd counterpart NdZn2 shows antiferromagnetic order at 23K. Samples of Gd1-xNdxZn2 (0<x⩽1) were prepared by the melt-growth method. In Nd-substituted systems, the anomaly due to spin-reorientation disappeared. For x⩾0.6, field-induced metamagnetic transitions were observed, indicating an antiferromagnetic ground state. This complex magnetism may originate from competition between ferromagnetic and antiferromagnetic interactions. Magnetic entropy change ΔSm was calculated based on the magnetization measurements. ΔSm was suppressed by Nd substitution for x values up to 0.6. For x=1 (NdZn2), the maximum value of ΔSm was −9J/K kg, which is almost the same as those of other Nd-based magnetocaloric materials.

A first principles study of Nd doped cubic LaAlO3 perovskite: mBJ+U study

The structural, electronic and magnetic properties of Nd-doped Rare earth aluminate, La1−xNdxAlO3 (x=0–100%) are studied using the full potential linearized augmented plane-wave (FP-LAPW) method within the density functional theory. The effects of Nd substitution in LaAlO3 are studied using super-cell calculations. The electronic structures were computed using modified Beck Johnson (mBJ) potential based approximation with the inclusion of Coulomb energy (U) for Nd-4f state electrons. The La1−xNdxAlO3 may possess half metallic behavior on Nd doping with finite density of states at EF. The direct and indirect band gaps were studied as a function of Nd concentration in LaAlO3. The calculated magnetic moments in La1−xNdxAlO3 were found to arise mainly from the Nd-4f state electrons. A probable half-metallic nature is suggested for these systems with supportive integral magnetic moments and high spin polarized electronic structures in these doped cases at EF. The controlled decrease in band gap with increase in concentration of Nd doping is a suitable technique for harnessing useful spintronic and magnetic devices.

Effect of substitution of minor Nd for Y on mechanical and damping properties of heat-treated Mg–Zn–Y–Zr alloy

This work mainly investigated the effect of Nd substitution on the microstructure, mechanical properties and damping capacity of Mg–Zn–Y–Zr alloy. Obtained results indicate that the phase constituent of the Mg–Zn–Y–Zr alloy and the chemical composition of W-phase vary with the partial substitution of Nd for Y. After solution treatment at 480°C for 8h, the secondary phases dissolve into the matrix and ZnZr particles precipitate at grain interiors. During subsequent aging treatment, higher density of β1′ and β2′ phases, Mg12Nd phase, long period stacking ordered (LPSO) and stacking fault (SF) structures precipitate in Mg–Zn–Y–Zr alloy with Nd substitution. The precipitation strengthening further help the ultimate tensile strength and yield strength of the alloy with Nd substitution reach up to 268MPa and 164MPa, respectively. The damping capacities of the investigated alloys decrease dramatically after heat treatment. The decline in damping of solution-treated alloys can be ascribed to the increasing number of solute atoms and ZnZr particles. Due to the stacking fault probability, LPSO and SF structures induced by the Nd substitution are believed to be the new damping source to contribute to the damping capacity of Mg–Zn–Y–Zr alloy besides dislocations.

Effect of Nd Substitution on the Structural and Magnetocaloric Properties of Gd&lt;sub&gt;5&lt;/sub&gt;Si&lt;sub&gt;2&lt;/sub&gt;Ge&lt;sub&gt;2&lt;/sub&gt;

In the present work, Nd substituted Gd5-xNdxSi2Ge2 with x = 0.05, 0.1 and 0.2 have been synthesized by arc melting and the effect of Nd substitution on the structural and magnetocaloric properties of Gd5Si2Ge2 has been investigated. The composition with x=0.05 undergoes a first order phase transition with a Curie temperature of 275 K. With the increase in Nd content to x=0.1 and x=0.2, the compounds undergo a second order magnetic transition at 300 K and 293 K respectively. Maximum entropy changes (-ΔSM) for Gd5-xNdxSi2Ge2 alloys with x = 0.05, 0.1 and 0.2 are 12.8, 7.6 and 7.2 J/kg K, respectively, for 50 kOe. The critical exponent analysis of the paramagnetic to ferromagnetic transition and the scaling behaviour of field dependence of MCE for x=0.1 and 0.2 compositions is also carried out.

Effect of Nd substitution on physical properties of multiferroic compound BiFeO3

Multiferroic materials have attracted great attention due to their potential applications in multifunctional devices. In this work, powders of Bi1−xNdxFeO3 (BNFO) with x = 0.00, 0.05, 0.15 and 0.20 were successfully synthesized by a sol–gel method using bismuth nitrate, iron nitrate and neodymium nitrate as sources. The BNFO powders were annealed at 500 °C. X-ray diffraction patterns revealed the formation of single phases BiFeO3 and BNFO. We observed that the neodymium substitution leads to the change of the BiFeO3 crystal structure from rhombohedral with space group R3c (α-phase) to pseudo-cubic symmetry Pm3 m. A high temperature variety (γ-phase) of multiferroic BiFeO3 compound has been stabilized for 15 % of neodymium content. The morphology of the particles seemed to be approximately spherical, the particle size of the BNFO is between 23 and 67 nm. Those powders show both magnetic transition at Neel temperature (TN) and ferroelectric transition around Curie temperature (TC). In addition a clear ferromagnetic component is observed for all powders. The variations of dielectric constant and dielectric loss, proves a possible coupling between the electric and magnetic dipole in these systems.

Glass-Forming Ability and Thermal Stability of Gd&lt;sub&gt;55-x&lt;/sub&gt;Nd&lt;sub&gt;x&lt;/sub&gt;Co&lt;sub&gt;20&lt;/sub&gt;Al&lt;sub&gt;25&lt;/sub&gt; Metallic Glass

The effects of Nd substitution in Gd55-xNdxCo20Al25 (x=0, 5, 10, 15 and 20) amorphous ribbon samples on glass-forming ability and thermal stability are studied. The change of microstructure cannot be identified by X-ray diffraction. The forecast of glass-forming ability following Fang’s method shows the increase with x, which is further confirmed experimentally by the increasing reduced glass-transition temperatures. The thermal stability has a minimum at x=10, and it is suggested to be due to the different effects of the reducing of Gd and the increase of Nd.

Effects of Rare-Earth Doping on Dielectric Properties of CaCu3Ti4O12Ceramics

The Ca1−xNdxCu3Ti4O12(x = 0.0%, 0.1%, 0.5% and 1.0%, respectively) ceramics were synthesized by the solid-state reaction method in the temperature range of 1000°C to 1100°C, and single-phase structures with space group Im3 were obtained up to x = 1.0%. The effects of Nd-substitution on the dielectric properties and conductivity of Ca1−xNdxCu3Ti4O12ceramics were investigated and discussed. The room temperature dielectric constant and dielectric loss of Ca1−xNdxCu3Ti4O12ceramics slightly decreased with x = 0.1% and 0.5%, but increased with x = 1.0%. The Nd-substitution has little effect on the giant dielectric constant step but a strong effect on the high-temperature dielectric relaxations.

Effect of Nd substitution on the microstructure and electrical properties of Bi7Ti4NbO21 piezoceramics

Abstract Neodymium (Nd) doped intergrowth bismuth layer-structured ferroelectric compounds Bi 7− x Nd x Ti 4 NbO 21 ( x = 0, 0.5, 0.75, 1.0, 1.25, 1.5, 1.75 and 2.0) were synthesized through a solid-state method. The influence of the Nd 3+ substitution of Bi 3+ on the lattice, microstructure and electrical properties of these compounds were investigated. The X-ray diffraction and Raman scattering analyses demonstrate that a phase transition from orthorhombic to pseudo-tetragonal occurs in these compounds, relying on substitution proportions and sites of Nd 3+ for Bi 3+ . With the increasing Nd 3+ dopants, the growth of plate-like grains along the a – b plane and a secondary intergranular metallic Bi phase were retarded which resulted in the increases of sintering temperature, density and electrical resistance of the doped ceramics. The resultant ceramic with x = 1.25 possesses a piezoelectric coefficient d 33 up to 16.3 pC/N with a Curie temperature T C above 750 °C were obtained for the compound.

Effects of Nd-substitution on microstructures and dielectric characteristics of CaCu3Ti4O12 ceramics

Ca1−3x/2NdxCu3Ti4O12 (x = 0, 0.1, 0.2) ceramics were prepared by a solid state reaction process, and single-phased structures were obtained for all the compositions. The dielectric characteristics of pure and Nd-substituted CaCu3Ti4O12 ceramics were investigated together with the microstructures. The mixed-valent structures of Cu+/Cu2+ and Ti3+/Ti4+ in the present ceramics were confirmed by X-ray photoelectron analysis. The dielectric relaxation in the low temperature range was examined in detail and the variation of dielectric constant and dielectric loss was attributed to the modification mixed-valent structures.

The effect of Nd substitution on the electrical properties of Bi3NbTiO9 Aurivillius phase ceramics

The effect of Nd substitution on the microstructures and electrical properties of Aurivillius phase ferroelectric Bi3NbTiO9-based ceramics has been studied. All of the Bi3−xNdxNbTiO9 (0≤x≤1) ceramics are ferroelectrics. The Curie point TC decreased with increasing Nd doping content x. The Bi3−xNdxNbTiO9 ceramics exhibited a sharp ferroelectric-paraelectric phase transition at small x values (x≤0.6), whereas a diffuse phase transition was observed at higher x values (x≥0.8). Both the piezoelectric constant d33 and the dc electrical resistivity of Bi3NbTiO9 ceramics were greatly enhanced by Nd substitution on the A sites. The improved properties can be attributed to the fact that Nd substitution depressed the generation of oxygen vacancies. A combination of high d33 values, high resistivity, and high TC points (&amp;gt;700 °C) suggests that the Bi3−xNdxNbTiO9 ceramics with x≤0.6 could be good candidates for high-temperature piezoelectric applications.

Effect of Nd substitution on the magnetic order inCexNd1−xB6solid solutions

Neutron powder-diffraction measurements have been performed on ${\text{Ce}}_{x}{\text{Nd}}_{1\ensuremath{-}x}{\text{B}}_{6}$ ($x=0.5$, 0.6, 0.7, and 0.8) solid solutions to determine the type of magnetic order occurring in these compounds as a result of the interplay between magnetic dipole exchange and antiferroquadrupolar interactions. In the Ce-rich range, the sequence of two magnetic phases, with an incommensurate order $[\mathbf{k}=(1/4\ensuremath{-}\ensuremath{\delta},1/4\ensuremath{-}\ensuremath{\delta},1/2)]$ forming below ${T}_{N}$ followed by a lock-in-type transition at lower temperature, is quite similar to that reported earlier for ${\text{Ce}}_{x}{\text{Pr}}_{1\ensuremath{-}x}{\text{B}}_{6}$. For $x=0.5$, on the other hand, the same antiferromagnetic order as in pure ${\text{NdB}}_{6}$ first occurs at ${T}_{N}$, then coexists with an incommensurate component below the lower transition temperature. These results are in good agreement with previous resistivity measurements and support the idea that Ce and Nd magnetic moments in this system can be relatively decoupled.

Effects of Nd substitution on magnetic and magneto-optical properties of TbCo/Cr films

NdTbCo/Cr amorphous films with high perpendicular magnetic anisotropy were prepared onto glass substrates by rf magnetron sputtering. The effects of Nd substitution on the magnetic and magneto-optical properties of TbCo/Cr films were investigated. It was found that partial Tb substitution by Nd would increase the saturation magnetization and the Kerr rotation angle, change the temperature dependence of magneto-optical characteristics. These results can be explained by the ferrimagnetic structure of the rare earth-transition metal alloy. When the magnetic layer composition was (Nd0.265Tb0.735)31Co69, a saturation magnetization of 247 emu/cm3 and a coercivity of 3.8 kOe at room temperature could be obtained.