Gd Substitution Research Articles

Effect of A-site disorder and reduced grain size on low temperature resistivity minima and magnetoresistance behaviour in Nd0.7-xGdxSr0.3MnO3 (0 ≤ x ≤ 0.3)

ABSTRACT The present work provides a detailed investigation of the electronic- and magneto-transport properties of bulk and nanostructured Nd0.7-xGdxSr0.3MnO3 (x = 0, 0.1, 0.2 and 0.3) polycrystalline manganites. We have specially addressed the issue of the observed minimum in the temperature dependent resistivity of these manganites in the low temperature regime (<50 K). It is observed that increase of A-site disorder due to progressive substitution of Gd and decrease of grain size enhances the observed resistivity minima. Different theoretical models have been employed to analyze the resistivity data in the low temperature regime. It has been established that the quantum interference effect due to electron–electron interaction, most likely, is the dominant factor of the observed resistivity minimum and upturn in resistivity in the lower temperature regime. The effect of phase separation is also found to play a key role in the electronic-transport of the materials. Further the magnetoresistance is found to increase with the increase of Gd concentration as well as with the decrease of grain size in the low temperature regime. The origin of magnetoresistance has been critically analyzed.

A Lu3Sc2Ga3O12: Eu3+ red-emitting phosphor with excellent optical properties and thermal stability was obtained by partially replacing Lu3+ with Gd3+ / Y3+

A novel red phosphor Lu3(1-x)Sc2Ga3O12: xEu3+(0 ≤ x ≤ 0.3) was successfully prepared by high temperature solid state method. The Lu2.4Sc2Ga3O12: 0.2Eu3+ phosphor shows strong high internal quantum efficiency and thermal stability with values of 64.79 % and 87.0 %, respectively. Based on Lu2.4Sc2Ga3O12: 0.2Eu3+ phosphor, the partial replacement of Lu3+ ions in the host by Gd3+ / Y3+ ions changes the local crystal field environment of Eu3+ ions, resulting in wonderful changes in the luminous center, and the luminous intensity at 593 nm is increased by 3.66 and 3.54 times, respectively. The decay time of Eu3+ ions is analyzed from the perspective of dynamics, and the reasons for the enhancement of luminescence after partial replacement of Lu3+ ions are discussed in detail from two aspects of phosphor structure and crystal field effect around Eu3+ ions. In addition, with the substitution of Gd3+ / Y3+ ions, the thermal stability of the sample is 90.3 %/89.4 % with excellent low thermal quenching. The thermal quenching mechanism is described by combining Debye temperature and activation energy. The sample also has a high internal quantum efficiency IQE=79.03 % / 78.24 %. Finally, under the excitation of 365 nm chip, the phosphors of Lu2.34Sc2Ga3O12: 0.2Eu3+, 0.02Gd3+ and Lu2.34Sc2Ga3O12: 0.2Eu3+, 0.02Y3+ synthesized R-LED device has extremely high color rendering index, Ra is 78.23/77.15 and color temperature is 1640.38 K/1642.97 K. The experimental results show that the Lu2.34Sc2Ga3O12: 0.2Eu3+, 0.02Gd3+ / Y3+ phosphors prepared has a wide application prospect in w-LED devices.

Enhanced thermal stability of nanocrystalline melt-spun Nd-Pr-Fe-B alloys by Gd substitution

Thermal demagnetization of Nd-Fe-B permanent magnets at elevated temperature presents a noteworthy challenge. Current research endeavors are concentrated on enhancing the thermal stability of Nd-Fe-B magnets. This study investigates the use of the cost-effective element Gd as a substitute for Nd in nanocrystalline melt-spun [(Nd0.8Pr0.2)1-xGdx]14.3Fe76.9B5.9M2.9 (M = Co, Cu, Al and Ga) (wt.%; x = 0–0.6) alloys. Although Gd substitution is not conducive to the magnetic properties of the alloys at room temperature, the Gd-substituted alloys exhibit excellent high-temperature performance. The Curie temperature (Tc) of the RE2Fe14B phase increases from 582 K to 643 K, with increasing Gd substitution from 0 to 0.6. The α and β coefficients for Gd-free (x = 0) alloy are −0.120 %/K and −0.468 %/K, respectively. By Gd substitution, they respectively increase to −0.068 %/K and −0.295 %/K for x = 0.6 alloy, which are superior to that of reported nanocrystalline Nd-Fe-B alloys and commercially sintered Nd-Fe-B magnets. Microstructural analysis revealed that Gd substitution promotes grain refinement. Furthermore, it was observed that Gd is uniformly distributed across both the grain boundary and main grains. Overall, this study offers a cost-effective and straightforward approach for enhancing the thermal stability of Nd-Fe-B magnets.

Gadolinium-doped SrFeO3 as a highly active and stable electrode for symmetrical solid oxide fuel cells

Symmetrical solid oxide fuel cells (SSOFCs) with identical electrodes have gained interesting attention because of their simplified fabrication procedure and reduced processing costs. However, their development is limited by their electrocatalytic activity and stability of the electrode materials used. Here, we report a prototypical SrFeO3-δ-based perovskite oxide with formula GdxSr1-xFeO3-δ (GSF) as a highly effective SSOFC electrode material. It was found that A-site Gd substitution in SrFeO3-δ greatly improved its structural stability under reducing atmosphere. Furthermore, doping Gd was able to significantly enhance the electrochemical activity, achieving area-specific resistances of 0.18 Ω cm2 for the cathode and 0.003 Ω cm2 for the anode at 800 °C, respectively. The lower polarization resistance could be attributed to the abundant surface oxygen species through the Gd-doping in SrFeO3-δ. Benefiting from superior electrochemical activity and structural stability, the symmetrical cell with GSF-0.2 electrode showed reasonable stability and electrochemical performance. These results show that the developed GSF perovskite oxide may be a promising candidate as electrode material for symmetrical SOFCs.

Sm substitution effect on the critical behaviour of Laves phase Gd1−xSmxCo2 intermetallic nearby the ferromagnetic-paramagnetic phase transition

In this work, we present a comparative and detailed study of the critical behavior near ferromagnetic-paramagnetic phase transition in the intermetallic Laves phase compounds Gd1−xSmxCo2, x = 0.5, 0.6 and 0.7. The investigated samples exhibit a second-order phase transition at Curie temperature TC. The critical exponents β, γ, and δ have been estimated through diverse techniques: the Modified Arrott plot, the Kouvel-Fisher plot, the critical isotherm technique, and the magnetocaloric effect method. The critical exponents values that were determined have been validated using the universal scaling hypothesis, wherein the isotherm magnetization curves M(H) converge into two distinct universal branches below and above TC. The substitution of Gd by Sm changes the universality class in the (Gd,Sm)Co2 compounds. For the sample Gd0.5Sm0.5Co2, the critical exponents obtained are closely consistent with the predictions of the 3D-Heisenberg model featuring a magnetic system with a short-range exchange interaction. While, for both samples Gd0.4Sm0.6Co2 and Gd0.3Sm0.7Co2, the values deviate from known theoretical models and might belong to an unconventional universality class with an intermediate-range exchange interaction.

Effect of Gd3+ ion doping on structural, optical, magnetic and dielectric properties on superparamagnetic Mg0.5Zn0.5Fe2−xGdxO4 (0 ≤ x ≤ 1) nanoparticles synthesized via oleic acid assisted chemical co-precipitation method

In the present study, different compositions having general formula Mg0.5Zn0.5GdxFe2−xO4, (x = 0, 0.025, 0.050, 0.075, 0.1) were synthesized using chemical co-precipitation method. The substitution of Gd3+ ions have exhibited profound impacts on the structural, morphological, magnetic, and optical parameters of Mg-Zn ferrites. Single-phase cubic spinel structure has been substantiated by X-ray diffractometer (X-ray diffraction, XRD) analysis for all compositions without any contamination peak. The values of the lattice constant and X-ray density both show an increasing trend when the Gd3+ ion concentration increases. (Fourier transformed infrared spectroscopy) FTIR spectra recorded in the mid-infrared region (4000–400 cm−1) exhibit two main absorption bands associated with the Oh and Td sites within the frequency range of 400–600 cm−1. Morphological studies using (High-resolution transmission electron microscopy) HR-TEM analysis reveal agglomeration of nanoparticles and the average particle size lies between 8 and 9 nm. Maximum magnetization displays an erratic trend with increasing Gd3+ ion concentration, although both retentivity and coercivity decreases. The hysteresis curve for samples of differing ratios of Gd3+ ions demonstrated the superparamagnetic nature. Tauc’s plot was employed to calculate the energy bandgap (Eg) of synthesized nanoparticles and Eg value were observed to decline from 3.563 eV to 3.521 eV with an increasing Gd3+ ion concentration. Impedance analyzer was used in the frequency range of 100 Hz–100 MHz to study dielectric properties at room temperature. The dielectric parameters declined as the frequency values increased. Due to lower values of dielectric parameters in Gd3+ ion doped Mg–Zn nano-ferrite, these materials are suitable in the fabrication of devices that need to operate at high frequencies such as switching memory storage devices. Moreover, these materials are appropriate for application in ferrofluids and medicinal treatments such as magnetic hyperthermia because of their low coercive field value.

Upconversion luminescence and temperature sensing performance of Zn2+-doped Ba2GdAlO5: Yb3+, Er3+ phosphors

Although upconversion luminescence (UCL) materials have attracted considerable attention in biomedical, lighting, anti-counterfeiting, and solar cells due to their excellent fluorescence properties, reports of the dibarium gadolinium aluminum oxide (Ba2GdAlO5) are scarce. Herein, we synthesized the single-phase Ba2GdAlO5 material with non-stoichiometric Ba2Gd1.06Al0.94O5 (denoted as BGAO, hereafter). The X-ray Rietveld refinement reveals that the substitution of Gd for Al accounts for the non-stoichiometry. Notably, the UCL properties of BGAO are realized by doping with Yb3+ and Er3+ ion pair, and it can be further enhanced significantly by co-doping with appropriate Zn2+ ions. The SEM images show that the particle size increases as the concentration of Zn2+ ions increases. The X-ray Rietveld refinement results of the Zn-doped BGAO: 0.1 Yb3+, 0.03Er3+ phosphor indicate the substitution of Zn2+ for Ba2+ and Al3+ ions simultaneously. Grain growth and lattice distortion account for the improvement of UCL properties after Zn2+ ions doping. In addition, the temperature sensing performance of the Zn2+-doped sample has been researched based on the fluorescence intensity ratio (FIR) technique, and the maximum absolute and relative sensitivities (SA-max and SR-max) are obtained to be 4.8 × 10−3 K−1 at 498 K and 1.1% K−1 at 298 K, respectively. This work provides a candidate with high UCL intensity for potential applications in optical temperature sensors.

Magnetocaloric effect in Er[formula omitted]Gd[formula omitted]Al2 ([formula omitted]) alloys

Measurements of magnetization (M) were performed on a series of Er1−xGdxAl2 (x= 0.1, 0.25, and 0.5) alloys. ErAl2 and GdAl2 are ferromagnets with the Curie temperatures (TC) of 14 K and 168 K, respectively. Er1−xGdxAl2 also showed a ferromagnetic order at TC= 21 K for x= 0.1, 57 K for x= 0.25, and 89 K for x= 0.5. Upon cooling, M(B) curves of Er1−xGdxAl2 for 0.1≤x≤0.5 exhibited a metamagnetic behavior. The field cooled M for Er1−xGdxAl2 increased below 30 K, indicating a spin-reorientation transition. The magnetic entropy change (ΔSm) for x=0.1 peaked at TC, while a peak or kink was observed for x= 0.25 and 0.5 in ΔSm near 25 K, distinct from a ferromagnetic order. The spin-reorientation due to the Gd substitution is attributed to the magnetic properties and broadened ΔSm(T) curves for Er1−xGdxAl2 alloys.

Evidence of Gd substitution for Y in YBCO films with Gd excess

Gd-YBa2Cu3O7-δ (Gd-YBCO) thin films with 10 mol% and 20 mol% excess-Gd concentration with respect to Y were investigated at the Gd L3 and Y K core absorption edges by EXAFS spectroscopy with the aim of determining the local structure of the Gd dopant. To this purpose, EXAFS data were collected also on GdBa2Cu3O7-δ (GdBCO) and pristine YBCO films and on Gd2O3 and Y2O3 model compounds for comparison with the YBCO films with Gd excess. The EXAFS analysis was based on Y and Gd oxides as well as on a cluster obtained by Density Functional Theory (DFT) where Gd atoms were inserted substitutional to Y atoms. The EXAFS data clearly reveal the incorporation of Gd in the lattice as substitute of Y and no evidence of segregated Gd oxide was found within the film matrix.

The Substitution of Rare-Earth Gd in BaScCuTe3 Realizing the Band Degeneracy and the Point-Defect Scattering toward Enhanced Thermoelectric Performance.

Zintl compounds have continuously received significant attention, primarily due to their structural characteristics that align with the properties of the electron crystal and phonon glass. In this study, the crystal structure and thermoelectric properties of the quaternary Zintl chalcogenide BaScCuTe3 are investigated. The band structure calculations for BaScCuTe3 reveal a slight energy split of 0.08 eV between the second valence band and the valence band maximum, suggesting the presence of multiband-transport behaviors. Substitution of rare earth Gd for Sc is conducted, which significantly increases the hole concentration from 4.1 × 1019 cm-3 to 8.2 × 1019 cm-3 at room temperature. Meanwhile, the Seebeck coefficient increases because of the participation of the second valence band. A maximum power factor of 6.56 μW/cm·K2 at 773 K is obtained, which is 72% higher than that of the pristine sample. Moreover, the lattice thermal conductivity decreases from 0.57 W/m·K for BaScCuTe3 to 0.48 W/m·K for BaSc0.97Gd0.03CuTe3 at 773 K, owing to the introduction of point-defect scattering. As a result, there is a noteworthy improvement in the thermoelectric figure of merit zT, increasing from 0.44 for the undoped sample to 0.85 for BaSc0.98Gd0.02CuTe3. Considering these findings, BaScCuTe3 exhibits great potential and holds promise for further investigation in the field of thermoelectric materials.

Tailoring Zr-doped tungsten bronze (Sr,Ba,Gd)Nb2O6 relaxor ferroelectric with high electrical insulation interface for dielectric capacitor

Tetragonal tungsten bronze structure (TTB) compounds have attracted tremendous interest for their applications in energy storage, especially as dielectric capacitor mediums. However, constrained by the inverse correlation of polarization and electric breakdown field in relaxor ferroelectrics, there is still a major challenge in improving energy density. To addresse this challenge, a viable strategy of constructing relaxor behavior with robust electrical insulation in TTB-type Sr0.485Ba0.47Gd0.03Nb2-xZrxO6 (SBN-Gd-Zrx) by introducing ZrO2 during the preparation process was proposed. By introducing Zr4+ in the B-site, we have revealed how Zr4+ affects the dielectric and ferroelectric characteristics to explore the intrinsic relaxation. Based on the analysis of Rietveld refinement against synchrotron X-ray powder diffraction and Raman results, the substitution of Gd3+ and Zr4+ for Sr2+ and Nb5+ in Sr0.53Ba0.47Nb2O6 caused a decline in tetragonality and a shrinkage of the unit cell due to the lattice defect of [GdSr]• and [ZrNb]', which mutually compensates effectively alleviate the distortion of BO6 and then favors the balance of polarization and dielectric constant. The accrual of additional ZrO2 at grain boundaries significantly enhances electrical insulation characteristics, as validated by complex impedance spectroscopy. At near room temperature, all Zr-doped SBN-Gd compounds of the series exhibit heightened relaxation and undergo a phase transition from ferroelectric to paraelectric. As a result, in tandem with the synchronous augmentation in breakdown electric field (EB) and saturation polarization (Pm), optimal energy storage characteristic is realized in the SBN-Gd-Zr0.2 sample. It attains a remarkable Wrec of 2.67 J/cm3 and an efficiency ƞ of 91.21 %, showcasing excellent suitability in terms of different frequencies and temperatures, which far exceeds that of Gd-modified SBN ceramics and pure SBN ceramics. These results exemplify an efficacious strategy for designing novel TTB dielectrics by coupling relaxor modulation with electrical insulation, and position them competitively for implementation in dielectric storage capacitors utilized in pulsed power devices.

Reddish-orange emitting Eu2−x Gd x Ge2O7 pyrogermanate ceramic phosphors: synthesis and role of Eu3+/Gd3+ substitution on the optical features

In this work, highly luminescent pyrogermanates were successfully synthesized through the solid-state reaction route, and the role of gradual Eu3+ substitution for Gd3+ on the structure and photoluminescent properties of Eu2−x Gd x Ge2O7 pyrogermanates was investigated. Pure Eu2Ge2O7 ceramic is triclinic, belonging to the P1 (#1) space group, and by increasing the x values, the crystal structure changes with the partial substitution of Eu3+ ions by the Gd3+ ions into the chemical lattice. The other phase-pure ceramic, Gd2Ge2O7, belongs to the tetragonal P41212 (#92) space group. Complete solid solubility was attained for x ⩽ 1.6, where Gd3+ replaced Eu3+ in the triclinic structure. It was verified that the band gap energies are dependent on the crystalline structure, increasing as Gd replaced Eu in the Eu2−x Gd x Ge2O7. The lowest band gap value (5.13 eV) was observed for the triclinic Eu2Ge2O7, and the highest one (5.88 eV) for the tetragonal Gd2Ge2O7. Highly intense reddish-orange emission (quantum efficiency up to 91.9%), through excitation at charge transfer band and Ln3+ f–f transitions were evaluated as the Gd substitution rises. Substitution-sensitive phase change at the nanoscale was monitored by Eu3+ emission, validating the presence of Eu3+ in the triclinic and/or tetragonal phase depending on the chemical composition (or the Gd3+/Eu3+ ratio). The chromaticity diagram figured out a reddish-orange emission, making them promising materials for high-entropy and photonic devices as solid-state lighting using excitation by near UV light-emitting devices.

Oxygen vacancy diffusion and dynamics in Gd-doped CeO2: A GGA+U study

Using a generalized gradient approximation + Hubbard U method in the framework of density functional theory, we investigate the oxygen vacancy (VO) diffusion and dynamics in 3 × 3 × 3 CeO2 supercells with two Gd substitutions for Ce and an oxygen vacancy. Results show that (i) VO always migrates along the <100> direction, and (ii) VO would rather migrate across the Ce–Ce edges than across Ce–Gd or Gd–Gd edges. Especially, Gd only positively influences the migrations of oxygen vacancies within the third nearest neighbor, indicating that the increased Gd doping is required for extending the positive influence to the long-distance diffusion of oxygen vacancy, which offers an accountable explanation for the enhanced ion conduction experimentally observed in CeO2 with high Gd doping. The negative influence of heavy Gd doping on the VO diffusion is also discussed in detail. The outcome of the current work has implications in illuminating the role of dopants toward expediting the oxygen vacancy diffusion and in promoting the performance in CeO2-based materials and devices for environmentally friendly applications.

Effect of Gd substitution on structure, optical and magnetic properties, and heating efficiency of Fe3O4 nanoparticles for magnetic hyperthermia applications

This work presents the synthesis of Fe3-xGdxO4 nanoparticles and the investigation of the impact of Gd content (x) on structural characteristics of nanoparticles, including lattice parameters, crystallite size, and X-ray density. The high-resolution images of Transmission Electron Microscopy reveal that the synthesized Fe3-xGdxO4 nanoparticles have a narrow distribution in size statistics between 9 and 12.5 nm. Interestingly, analyzing different prepared samples reveals that both the saturation magnetization and magnetic anisotropy decrease simultaneously with the increase of band gap while remaining independent of the specific absorption rate (SAR) value. The SAR is greater than that of pure Fe3O4 nanoparticles. In a specific case of Fe2.75Gd0.25O4 sample where the optimal value of x is 0.25, the highest SAR value obtained is 237.4 W/g. Besides, the experimental results demonstrate an optimal doping content with the highest SAR value of Fe2.75Gd0.25O4 nanoparticles along with the theoretical explanation by analyzing the Linear Theory Response framework based on the relationship between magnetic anisotropy and diameter with SAR value. The theoretical and experimental evidence fully demonstrate that doping is an effective approach for optimizing as-synthesized NPs to enable efficient hyperthermia applications.

First-Principles Study on the Mechanical Properties of Gd-Doped BCZT Ceramics

Due to their remarkable piezoelectric characteristics, (BaCa)(ZrTi)O3 (BCZT) ceramics exhibit vast potential for being employed in cutting-edge electromechanical apparatus. Extensive experimental studies have been conducted to better meet the practical needs of BCZT-based materials, focusing on their mechanical performance. However, there is a serious lack of research on the theoretical computational aspects. Here, first-principles calculations were utilized to evaluate the mechanical properties of BCZT-xGd ceramics. The structural models were established using the virtual crystal approximation (VCA) method. The investigated compounds demonstrate structural and mechanical strength, as evidenced by their negative formation energies and adherence to the Born stability criteria. Compared to pure BCZT, the substitution of Gd leads to a significant enhancement in the system’s elasticity and stiffness. The BCZT-0.05Gd with B-site doping demonstrates the highest level of Vicker’s hardness (HV), with the noteworthy observation that the inclusion of Gd concomitantly augments its machinability performance. Upon the incorporation of the Gd element, the anisotropic elasticity in the systems gradually transitions into isotropic elasticity, which favors a more uniform stress distribution and consequently reduces sensitivity to the formation and propagation of microcracks. These results indicate that BCZT-xGd exhibits potential for application in electromechanical systems.

The electronic, magnetic and optical properties of GaN monolayer doped with rare-earth elements

Structural, electronic, magnetic, and optical properties of rare earth (RE) metal element doped GaN monolayers are investigated using density functional theory, where RE = Nd, Sm, Eu, Gd, and Er. The introduction of RE atoms causes structural deformation of the GaN monolayer. The induced local magnetic moments are observed to be 4.00, 6.00, 7.00, 8.00, and 2.00 μB in Nd, Sm, Eu, Gd, and Er adsorbed GaN monolayers, respectively, while the values are 3.00, 5.00, 6.00, 7.00, and 3.00 μB in the substitution of Ga atoms. When Nd, Gd and Er adsorbed in GaN monolayer Fermi levels are shifted to the conduction band leading to metallicity, while in the case of Sm and Eu adsorption impurity states are found near the Fermi level. On the contrary, Eu, Gd and Er substitution of Ga atoms leads to the Fermi energy level being shifted below the VBM. In the Nd and Eu substitution system, the f-state is found near the Fermi level and the Nd-f state crosses the Fermi level. Optical absorption, transmission and refraction coefficients show that the addition of RE atoms can significantly enhance the prospects of GAN monolayers in visible as well as infrared applications. This research provides an outlook for the development of GaN monolayer-based optoelectronic as well as spintronics devices.

Enhanced elastocaloric effect and mechanical properties of Gd-doped Ni-Co-Mn-Ti-Gd metamagnetic shape memory alloys

Improving elastocaloric effect (eCE) and mechanical properties is the key to developing high-performance eCE cooling materials. In this paper, the metamagnetic shape memory alloys Ni35.5Co13.5Mn35Ti15-xGdx (x = 0–0.9) were successfully prepared by arc melting method, and the effects of Gd substitution for Ti on the martensitic transformation (MT) temperature, phase composition, microstructure, eCE and mechanical properties of the alloys were systematically investigated. With the introduction of Gd elements, the transformation temperature shifts to a low temperature, and the mechanical properties of the alloy are also enhanced. The fracture strength increased from 980 MPa (x = 0) to 1142 MPa (x = 0.9). At room temperature (RT), a large adiabatic temperature change of + 13.5 K/− 12.7 K is obtained after loading/unloading, and a constant temperature change of + 5.6 K/− 5.5 K is obtained without apparent degradation under the compressive stress of 400 MPa during 61 cycles for all-d metal Heusler Ni36.5Co13.5Mn35Ti14.9Gd0.1 alloy. The adiabatic temperature change of 13.5 K exceeds the elastocaloric temperature change of most NiMn-based alloys available at present, and the mechanical properties of Ni-Co-Mn-Ti-Gd alloy are at a high level among the NiMn-based alloys. The precipitation of the Gd-rich second phase along the grain boundaries is intrinsically responsible for the improved mechanical properties.

Tuning of efficient energy storage and fast switching capability in La2Zr2O7 pyrochlore nanoparticles mediated by Gd-substitution

Electrostatic capacitors are widely investigated to fulfill the energy storage demand and their utilization in microelectronic devices. The efficient energy storage capabilities of pyrochlores with less loss factor make them eminent in energy storage contesters. Here we synthesized a series of La2-xGdxZr2O7 with x = 0.0, 0.4, 0.8, 1.2, 1.6, and 2.0 substitution contents via the sol-gel auto-combustion process. The substitution of Gd on the La site compresses the pyrochlore structure without any phase transformation which leads to an increase in the X-ray density. A gradual decrease in grain size with an increase in substitution contents causes the increase in surface adhesion and agglomeration. Energy-dispersive X-ray spectra confirm the formation of exact compositions for all the samples. The energy storage capability of the synthesized series is examined by the PE loop, leakage current, PUND sequence, and normalized capacitance. An increase in energy storage abilities is noted with an increase in Gd concentration. The small value of energy loss, the highest recoverable energy density with a larger value of effective and normalized capacitance is recorded for Gd1.6La0.4Zr2O7 composition which exposed the potential of this composition for microelectronics devices to fulfill the energy storage demand.

Enhanced X-band absorption and shielding performance of Gd-substituted barium hexaferrite

Gd- substituted barium hexaferrite has been synthesized by solid-state ceramic method to explore its X-band (8.2 – 12.4 GHz) absorption and shielding performance. The structural, magnetic, and microwave properties of the synthesized hexaferrite were studied by X-ray diffraction (XRD), micro-Raman spectroscopy, field emission scanning electron microscopy (FESEM), vibrating sample magnetometer (VSM), and vector network analyzer (VNA). XRD patterns confirmed the hexagonal magnetoplumbite phase formation in all samples. A noticeable red shift in the Raman spectra from 710 to 705 cm-1 and 323–327 cm-1 suggested the presence of Fe2+ ions at 4f1 tetrahedral and 12k octahedral sites, respectively. Microstructural studies on as-prepared samples confirm particle size reduction up to 1.86 µm with Gd substitution. A modest increase in magnetization and remanence value for 20% Gd was noted. Coercivity increased with substitution, whereas the anisotropy field and crystalline anisotropy constant reduced with Gd addition. An overall improvement in shielding efficiency and absorption was noted for Gd- substituted samples. A maximum average shielding efficiency of 16.47 dB and effective absorption of 99.99% was recorded for 10% Gd. Overall, microwave absorbance is improved up to 97% with Gd substitution, which suggests this material can also work as an absorber in microwave device applications.

Structural, magnetic and antibacterial studies of gadolinium doped cobalt ferrite nanoparticles synthesized at low temperature

In this work structural, magnetic and antimicrobial studies of gadolinium (Gd) doped cobalt ferrite nanopowder samples were synthesised through facile auto-combustion route using citric acid as combustion agent. The pristine nanopowders were sintered at 600 °C. X-ray diffraction (XRD), infrared spectroscopy (IR) measurements indicated the formation of a single spinel phase. The lattice constant gradually increased from 8.3801 Å to 8.3915 Å with increasing Gd concentration. The average crystallite size varied from 54 nm to 42.7 nm. The correlation between the cation distribution from XRD and the magnetic properties is discussed. The substitution of Gd ions significantly reduced the magnetisation from 60.6 to 36.6 emu g−1 and increased the coercivity. Antimicrobial activities of pure and Gd substituted cobalt ferrite are carried out against Gram-positive (Bacillus subtilis) and Gram-negative (Escherichia coli, Pseudomonas aeruginosa) and also against fungi strain (Aspergillus niger) pathogens, suggesting that Gd substitution significantly improves the activity of cobalt ferrite nanopowders.