Substitution Of Nd Research Articles

Effects of Nd-doping on optical and photovoltaic properties of barium titanate thin films prepared by sol–gel method

Nd-doped barium titanate thin films were prepared via sol–gel spin-coating method and effects of Nd content on microstructure, optical and photovoltaic properties have been investigated. The results show that Nd-doped barium titanate thin films are single tetragonal perovskite phase. Addition of neodymium to some extent can inhibit the grain growth. Substitution of Nd3+ ions for Ba2+ on A sites leads to the decrease of band gap. The remnant polarization begins to increase and reach the maximum and then decreases as Nd content increases. The short circuit photocurrent density, open circuit photovoltage and power conversion efficiency of Nd-doped barium titanate thin films begin to increase and reach the maximum and then decrease as Nd content increases.

Electrochemical hydrogen storage characteristics of as-cast and annealed La0.8-xNdxMg0.2Ni3.15Co0.2Al0.1Si0.05 (x=0–0.4) alloys

The La-Mg–Ni–based A2B7-type La0.8-xNdxMg0.2Ni3.15Co0.2Al0.15 (x=0, 0.1, 0.2, 0.3, 0.4) electrode alloys were prepared by casting and annealing. The influences of partial substitution of Nd for La on the structure and electrochemical performance of the as-cast and annealed alloys were investigated. It was found that the experimental alloys consist of two major phases, (La, Mg)2Ni7 phase with the hexagonal Ce2Ni7-type structure and LaNi5 phase with the hexagonal CaCu5-type structure, as well as some residual phase LaNi3 and NdNi5. The discharge capacity and high rate discharge ability (HRD) of the as-cast and annealed alloys first increase and then decrease with Nd content growing. The as-cast and annealed alloys (x=0.3) yield the largest discharge capacities of 380.3 and 384.3 mA·h/g, respectively. The electrochemical cycle stability of the as-cast and annealed alloys markedly grows with Nd content rising. As the Nd content increase from 0 to 0.4. The capacity retaining rate (S100) at the 100th charging and discharging cycle increases from 64.98% to 85.17% for the as-cast alloy, and from 76.60% to 96.84% for the as-annealed alloy.

Structure, Phase Transition Behaviors and Electrical Properties of Nd Substituted Aurivillius Polycrystallines Na0.5NdxBi2.5–xNb2O9(x= 0.1, 0.2, 0.3, and 0.5)

New high temperature Aurivillius piezoelectrics Na0.5Nd(x)Bi(2.5-x)Nb2O9 (NDBNx, x = 0.1, 0.2, 0.3, and 0.5) with Nd substitution for Bi at the A site were synthesized using a solid state reaction process. Crystal structures of NDBN0.2 and NDBN0.5 were refined with the Rietveld method with powder X-ray diffraction, and they crystallized in the orthorhombic space group A21am [a = 5.48558(8) Å, b = 5.46326(9) Å, c = 24.8940(4) Å, and Z = 4 for NDBN0.2 and a = 5.46872(5) Å, b = 5.46730(5) Å, c = 24.80723(25) Å, and Z = 4 for NDBN0.5], at room temperature. The refinement results and Raman spectroscopy of NDBNx verified that Nd occupied both the A site in the perovskite layers and the cation site in the (Bi2O2)(2+) layers. The Nd substitution induced an enhancement in cation disordering between the A site and the (Bi2O2)(2+) layer and an increase in the degree of the relaxation behavior for NDBNx. The ferroelectric to paraelectric phase transition temperature (Tc) of NDBNx ranged from 735 to 764 °C. Furthermore, the isovalent substitution of Nd for Bi had a great influence on microstructure (grain size and shape), defect concentration (mainly oxygen vacancies), preferred grain orientation (texture), and distortion of the octahedron. The coaction between these effects determined the structure characteristics, phase transition behaviors, and electrical properties of NDBNx.

Electrochemical performances of as-cast and annealed La0.8-x Nd x Mg0.2Ni3.35Al0.1Si0.05 (x = 0–0.4) alloys applied to Ni/metal hydride (MH) battery

The La–Mg–Ni-based A2B7-type La0.8-x Nd x Mg0.2Ni3.35Al0.1Si0.05 (x = 0, 0.1, 0.2, 0.3, and 0.4) electrode alloys were prepared by casting and annealing. The influence of the partial substitution of Nd for La on the structure and electrochemical performances of the alloys was investigated. The structural analysis of X-ray diffraction and scanning electron microscopy reveals that the experimental alloys consist of two major phases: (La,Mg)2Ni7 with the hexagonal Ce2Ni7-type structure and LaNi5 with the hexagonal CaCu5-type structure as well as some residual phases of LaNi3 and NdNi5. The electrochemical measurements indicate that an evident change of the electrochemical performance of the alloys is associated with the substitution of Nd for La. The discharge capacity of the alloy first increases then decreases with the growing Nd content, whereas their cycle stability clearly grows all the time. Furthermore, the measurements of the high rate discharge ability, the limiting current density, and hydrogen diffusion coefficient all demonstrate that the electrochemical kinetic properties of the alloy electrodes first augment then decline with the rising amount of Nd substitution.

Magnetic properties and magnetostriction of PrxNd1−xFe1.9 (0 ≤ x ≤ 1.0) alloys at low temperature

The crystal structure, magnetic and magnetostrictive properties of high-pressure synthesized PrxNd1−xFe1.9 (0 ≤ x ≤ 1.0) alloys were studied. The alloys exhibit single cubic Laves phase with MgCu2-type structure. The initial magnetization curve reveals that Pr0.2Nd0.8Fe1.9 has a minimum magnetocrystalline anisotropy at 5 K. The magnetostriction curve at 5 K shows that Pr0.2Nd0.8Fe1.9 has a very good low-field magnetostrictive property, and the magnetostriction of the PrxNd1−xFe1.9 alloy in high magnetic field is attributable mainly to Pr. The temperature dependence of the magnetostriction (λ‖) at the field of 5 kOe shows that the substitution of Nd reduces the K1 remarkably, and the values of λ‖ of Pr0.2Nd0.8Fe1.9 and Pr0.8Nd0.2Fe1.9 alloys are nearly five times larger than that of the PrFe1.9 alloy below 50 K; the λ‖ of Pr0.8Nd0.2Fe1.9 reaches up to 1082 ppm at 100 K, which makes it a potential candidate for application in this temperature range.

Influence of Nd Substitution by La in on Structural and Transport Properties for Sensing Applications

The structural and transport properties of manganites with and 0.2 prepared by solid state reaction route are studied. These compounds are found to be crystallized in orthorhombic structural form. A shift in the metal-semiconductor/insulator transition temperature () towards room temperature (289 K) with the substitution of Nd by La, as the value of is varied in the sequence (0, 0.1, and 0.2), has been provided. The shift in the , from 239 K (for ) to near the room temperature 289 K (for ), is attributed to the fact that the average radius of site-A increases with the percentage of La. The maximum temperature coefficients of resistance (TCR) of ( and 0.2) are found to be higher compared to its parent compound which is almost independent of . The electrical resistivity of the experimental results is explored by various theoretical models below and above . An appropriate enlightenment for the observed behavior is discussed in detail.

Improvement of (004) texturing by slow growth of Nd doped TiO2 films

In this work, we present preferred (004) texturing of sputter deposited titanium dioxide (TiO2) films on glass substrates as a consequence of Nd doping at very slow growth rate. Nd concentration was varied from 0.0 to 2.0 atomic percent (at. %) in TiO2 thin films deposited under identical growth conditions, i.e., the growth rate of 0.6 Å/s and at 500 °C. At 2 at. % Nd, complete texturing along (004) plane was observed, as indicated by the X-ray diffraction analyses. Morphology of the deposited TiO2 films from pure to 2 at. % Nd doped TiO2 films showed faceted to planar growth. Visualization of electrical and structural analysis (VESTA) software revealed that the change in the morphology was due to preferential growth in (004) orientation. Raman spectroscopy highlighted the phonon confinement in the Eg mode, and a red shift was observed due to an increase in the anti-symmetry in bonding with increased Nd concentration. XPS results confirmed the variation in oxygen vacancy concentration along with the reduction of Ti and Nd valance states with the change in the dopant concentration. Our experiments confirmed that the substitution of Nd at Ti sites was responsible for texturing in (004) orientation and this was possible by growing films at a very slow rate.

High-Temperature Electrical Transport Property of Misfit Cobaltite of Ca3-xNdxCo4-xCuxO9 (x = 0.0 – 0.4)

Polycrystalline samples of the Ca3-xNdxCo4-xCuxO9 (x = 0.0 - 0.4) were prepared by the sol-gel cum combustion method using sucrose to investigate the effects of the coupled substitution of Nd and Cu on Ca and Co sites simultaneously on electrical property of Ca3Co4O9 (Co349). The products were characterized by powder x-ray diffraction (XRD), thermogravimetry (TG) / differential thermal analysis (DTA) and scanning electron microscopy (SEM). Powder XRD patterns reveal the formation of single-phase products up to x = 0.4. Coupled substitution increases the solubility of Cu on Co site, in contrast to the limited solubility of Cu (x = 0.3) when separately substituted. TGA confirms the formation of the Ca3Co4O9 phase at around 680 0C. The grain size of the parent and substituted products is in the range of 200-250 nm. Electrical resistivity (ρ) measurement was performed in the temperature range of 300 - 800 K. Electrical resistivity (ρ) of parent sample shows metallic type conduction behavior up to 500 K and above 500 K, it shows semiconducting behavior. All the substituted compositions show semiconducting behavior with increasing electrical resistivity with increasing x. The conduction mechanism was also analyzed. Parent and substituted samples behave thermally activated conduction mechanism in the temperature range of 600 – 800 K.

Effect of Nd doping on the magnetic properties of charge-ordered Bi0.6−x Nd x Ca0.4MnO3 (0.0≤x≤0.6) perovskite manganites

We have studied structure, magnetic and transport properties of polycrystalline Bi0.6−x Nd x Ca0.4MnO3 (x=0.0, 0.1, 0.2, 0.3, 0.4, 0.5 and 0.6). Substitution of Nd at Bi sites induces a strong interplay between the magnetic and charge ordering. The charge-ordering temperature (T CO) decreases with increasing x. Further, the antiferromagnetic ordering temperature (T N) increases sharply at both extremes and remains nearly constant for x=0.2–0.4. At T<T N a transition to a metamagnetic glass-like state is also seen. Nd doping also leads to enhancement in the magnetic moment and a concomitant decrease in resistivity up to x=0.3 and then an increase in resistivity up to x=0.5. Furthermore, Nd doping promotes an antiferromagnetic to ferromagnetic type fluctuation in the materials at room temperature, as evidenced by the change in the value of the paramagnetic Curie temperature. We find that the local lattice distortion induced by the size mismatch between the A-site cations and the 6s2 character of Bi3+ lone pair electrons explains the observed peculiarity in magnetic and transport properties of Nd-doped Bi0.6Ca0.4MnO3.

Chemical compatibility, redox behavior, and electrochemical performance of Nd1−xSrxCoO3−δ cathodes based on Ce1.9Gd0.1O1.95 for intermediate-temperature solid oxide fuel cells

The effect of Sr substitution for Nd on Nd1−xSrxCoO3−δ (NSC) (x=0.3, 0.4, 0.5, 0.6, and 0.7) is investigated to evaluate NSC as a cathode material based on Gd0.1Ce0.9O1.95 (GDC) electrolyte for intermediate-temperature solid oxide fuel cells (IT-SOFCs). The NSC powders are prepared by the glycine nitrate method. At a given temperature, the electrical conductivity increases with increasing Sr content up to x=0.5 and then decreases for x>0.5. The redox behavior of NSC (x=0.3, 0.5, and 0.7) cathodes is studied by the coulometric titration at 700°C. In order to investigate the area specific resistances of NSC–GDC cathodes, symmetrical half cells (cathode/electrolyte/cathode) are measured using impedance spectroscopy at various temperatures in air under open circuit voltage (OCV) condition. The electrochemical performance of NSC–GDC cathodes is measured using an NSC–GDC/GDC/Ni-GDC anode supported cell. The maximum power density of NSC–GDC cathodes increases with increasing strontium content up to x=0.5 and then decreases at 700°C. In terms of electrical conductivity and electrochemical performance, Nd1−xSrxCoO3−δ (x=0.5) is more suitable as a cathode material based on GDC electrolyte in IT-SOFC applications.

An Ultra‐Broad Working Temperature Dielectric Material of BaTiO3‐Based Ceramics with Nd2O3 Addition

An ultra‐broad working temperature dielectric material, BaTiO3–Na0.5Bi0.5TiO3–Nb2O5–MgO–Glass with Nd2O3 addition, was investigated for the first time. Microstructure and dielectric properties of the well‐sintered samples were studied. XRD results showed the formation of tetragonal perovskite and the presence of a second phase of NaBiTi6O14. It is found that the addition of Nd2O3 produces a decrease in tetragonality of perovskite structure which could be interpreted by the substitution of Nd3+ ions into Ti sites. Bulk densities and dielectric properties were measured as a function of Nd2O3 concentration. The 0.4 mol% Nd2O3‐doped sample showed the optimal dielectric performance (εr = 1445, tan δ&lt;2.0%, ΔC/C ≤±12%) that satisfied EIA‐X9R specification. In particular, the ceiling working temperature was significantly enhanced from 200°C to 270°C by doping Nd2O3. Since it possesses large dielectric constant, low dielectric loss, and stable temperature character, this material shows promising applications for the ultra‐broad temperature range components, e.g., multilayer ceramic capacitors.

Structural and magnetic properties of Nd-doped strontium ferrite nanoparticles

Nanosized Nd-doped strontium ferrites, SrNdxFe12-xO19, with x=0.0–0.5, were successfully prepared through a chemical coprecipitation process. The samples were characterized by X-ray diffraction (XRD), X-ray fluorescence (XRF) and vibrating sample magnetometer (VSM). Various parameters such as lattice constants (a and c) and crystallite size were calculated from the XRD data. The crystallite size was in the range of 28–39nm. The specific saturation magnetization (Ms) and the coercivity (Hc) of strontium ferrites could be improved by substitutions of Nd3+ ions on Fe3+ ion basis sites. The Ms revealed magnetic behavior with respect to Nd3+ ion concentration, showing a decrease. The Hc increased with increasing Nd3+ ion concentration.

Enhancing the perpendicular anisotropy of NdDyFeB films by Dy diffusion process

A large coercivity and anisotropy enhancement in perpendicular NdDyFeB (120 nm)/Dy (tDy) films has been realized by a Dy grain-boundary diffusion process. The coercivity HC and the ratio Mr/Ms reach their maxima at tDy = 50 nm, and the magnetic domain sizes increase with increasing tDy. The HC and Mr/Ms increasing with tDy is due to the enhancement of the anisotropy of (Nd,Dy)2Fe14B grains by Dy substitution for Nd. The coercivity mechanism is a nucleation-type mechanism. Dy and Nd elements coexist at grain boundaries, forming a (Nd,Dy)-rich phase, which may promote the nucleation of reversal domains.

Conductivity and electrical modulus studies of La2−x Nd x Mo1.7W0.3O9−δ oxygen ion conductor

La2−xNdxMo1.7W0.3O9−δ (x = 0 − 0.5) and, for comparison, La2Mo2O9 compounds have been synthesized following solid state reaction technique. Temperature-dependent electrical conductivity of La2−xNdxMo1.7 W0.3O9−δ reveals suppression of the phase transition as compared to parent La2Mo2O9 compound. Partial substitution of Nd at the La site of La2Mo1.7W0.3O9−δ increases the conductivity of La2Mo1.7W0.3O9−δ in the entire temperature regime. In the intermediate temperature region (405 °C ≤ T ≤ 570 °C), the overall conductivity of La2−xNdxMo1.7W0.3O9−δ (0.1 ≤ x ≤ 0.5) is higher than that of the parent compound, and the conductivity of the compound with x = 0.1 is almost same with the La2Mo2O9 in the high temperature region (T ≥ 640 °C). Arrhenius to Vogel–Tamman–Fulcher (VTF) transition is observed in all doped specimens above 460 °C. Ion relaxation mechanism has been discussed in the framework of electrical modulus analysis in the temperature range RT–530 °C and is found to be non-Debye type of conductivity relaxation with the distribution of transition rates for hopping ions in the range of 0.60–0.70.

(Nd1.5Mg0.5)Ni7-Based Compounds: Structural and Hydrogen Storage Properties

The structural and hydrogen storage properties of (Nd(1.5)Mg(0.5))Ni(7)-based alloys (i.e., A(2)B(7)-type) with a coexistence of two structures (hexagonal 2H and rhombohedral 3R) are investigated in this study. In both 2H- and 3R-type A(2)B(7) structures, Mg atoms occupy Nd sites of Laves-type AB(2) subunits rather than those of AB(5) subunits because Mg substitution for Nd in the AB(2) subunits more significantly strengthens the ionic bond in the system. An increase in the A-atomic radius or the B-atomic radius stabilizes the 2H structure, but a decrease in the A-atomic radius or the B-atomic radius is favorable for formation of the 3R structure. The 2H-A(2)B(7) and 3R-A(2)B(7) phases in each alloy have quite similar equilibrium pressures upon hydrogen absorption and desorption, which show a linear relationship with the average subunit volume. The hydriding enthalpy for the (Nd(1.5)Mg(0.5))Ni(7) compound is about -29.4 kJ/mol H(2) and becomes more negative with partial substitution of La for Nd and Co/Cu for Ni but less negative with partial substitution of Y for Nd.

Effect of disorder particles size of Nd on electrical transport on a bulk of Pr2/3Ba1/3MnO3

Polycrystalline samples of (Pr1– xNd x)0.67Ba0.33MnO3 with concentrations of x = 0.0, 0.167, 0.33, 0.5, 0.67, 0.833, and 1.0 have been prepared using solid-state reactions. The analysis of X-ray diffraction data revealed that all of the samples were found to crystallize in the orthorhombic structure. The electrical property, Tp, was determined by using standard four-point probe resistivity measurements in a temperature range of 30–300 K. A shift of the metal-insulator transition temperature, Tp, to a lower value was observed when Pr doping was increased. The electrical resistivity data was analyzed using various theoretical models, and it has been concluded that the resistivity of the samples in a low temperature regime ( T &lt; Tp) are well-fitted using the expression [Formula: see text], implying the importance of grain/domain boundaries and electron–electron and two magnon scattering processes. In the high temperature regime ( T &gt; Tp), the resistivity data can be well described by small polaron hopping and variable range hopping mechanisms. In the semi-conducting portion, the activation energy ( Ea) has been investigated. The Ea increased as the doping concentration increased. Scanning electron microscope micrographs showed that the substitution of Nd3+ ions for the Pr3+ site in LaBaMnO3 leads to grain growth inhibition, disorder in the grain size, praseodymium segregation, and second phase formation.

Influence of gadolinium on microstructure and magnetic properties of sintered NdGdFeB magnets

The effect of Gd content on microstructure and magnetic properties of sintered Nd33.03−xGdxFe65.65B1.32 (x=0–2) was studied in this paper to improve the thermal stability of NdFeB and to reduce the raw material cost. The results showed that better magnet performance could be obtained by adding Gd (0–1.5 wt.%) with partial substitution of Nd in Nd33.03−xGdxFe65.65B1.32. It was also found that the Nd33.03−xGdxFe65.65B1.32 magnets showed the best performance when Gd addition increased to 1.0 wt.%. The temperature coefficient Br (α) could be improved from −0.15%/°C to −0.063%/°C (maximum work temperature 120 °C) and the Curie temperature could be improved from 315 °C to 323 °C because the Gd2Fe14B had positive temperature coefficient Br (α) and higher Curie temperature than that of Nd2Fe14B. The coercivity could be improved from 10.2 to 11.48 kOe and the microstructure was close to ideal microstructure. The magnetic performance decreased sharply by adding Gd (above 2 wt.%) with partial substitution of Nd in Nd33.03−xGdxFe65.65B1.32 because the Gd element concentrated in the grain boundaries.

The mechanism of enhanced magnetic properties of sintered permanent magnets by substitution of Pr for Nd

In this study, the influence of substitution of Nd with Pr on the magnetic of sintered permanent magnets was investigated. The samples were prepared by traditional powder metallurgical technique. The nominal composition of the alloys is (Nd 1− x Pr x ) 29Dy 1.3R 3.1Fe bal (R = Al 0.3Cu 0.2 Co 1.5 B 1Zr 0.1, wt%) with x varying from 0 to 1 in steps of 0.2. Experimental results show that the overall magnetic properties, especially the intrinsic coercivity and thermal stability of the magnets, could be improved by substituting Nd with Pr in the magnets. When the Pr replaces all Nd in the magnets, excellent performance magnets with Br = 13.65 KGs, Hcj = 22.13 KOe, (BH) max = 46.1 MGsOe are obtained with a low Dy content (1.3 wt%).

Structural and Electrical Properties of Direct-Patternable Bi4-XNdXTi3O12 Ferroelectric Thin Films

Variations in the structural and electrical properties of Bi4Ti3O12 ferroelectric thin films in the Aurivillius family were investigated by substituting Nd3+ for Bi as Bi4-xNdxTi3O12 (x = 0, 0.35, 0.65, and 0.85) using a direct-patternable photochemical metal-organic deposition method. Photoemission spectroscopic and X-ray absorption spectroscopic analyses revealed that as the substitution of Nd3+ for Bi increased until x = 0.65, the orthorhombicity decreased followed by an increase in covalent mixing and centro-symmetry of the Ti-O octahedrons. However, an increase in polarization of the Ti-O octahedron due to Jahn-Teller distortion was observed due to the generation of oxygen vacancies at x = 0.85.

The effect of substitution of Nd by Pr on the magnetic properties of melt-spun Nd–Fe–B nanocomposite alloys

The effect of partial substitution of Nd by Pr on the magnetic properties of exchange-coupled Fe3B/Nd2Fe14B nanocomposites with compositions (Nd1−yPry)4.5Fe77B18.5 (y = 0, 0.22, 0.45 and 0.66) has been investigated. Microstructural studies were carried out and correlated with the hard magnetic properties. The substitution of Nd by Pr improves iHc and (BH)max from 0.264 T and 73 kJ m−3 in the Pr-free alloy to 0.363 T and 106 kJ m−3, respectively, in the y = 0.45 alloy. Remanence magnetization decreases marginally on substitution. An increase in the Pr content beyond y = 0.45 leads to a deterioration of the hard magnetic properties, possibly due to a weakening of the exchange coupling interactions between the hard and soft magnetic phases.