Conventional Ceramic Method Research Articles

Synthesis and Characterization of Cu-Co Substituted Strontium Hexaferrite for Magnetic Applications

In this study, the structural and magnetic characterizations of a series of SrCoxCuxFe12-2xO19; 0.0 ≤ x ≤ 0.5 samples, which were produced by the conventional ceramic method, were carried out. The structure was examined by X-ray diffraction (XRD) technique and optical microscopy. A vibrating sample magnetometer (VSM) was used to characterize the ferrimagnetic properties. XRD patterns confirmed the presence of a single phase as Sr-hexaferrite while there were not any peaks of unreacted Fe2O3 phase. The densities varied between 92 – 98 %. XRD patterns of the Sr-hexaferrite samples were slightly modified because of the co-substitution of Cu-Co; however, the magnetic properties changed remarkably. The sample with Cu-Co of x = 0.1 content had the highest saturation magnetization (33.52 emu/g), remanence (19.74 emu/g), and coercivity (4.3 kOe). The synthesized magnetic samples were found to be suitable for the development of attractive ferrimagnetic properties for the current ferrite magnets.

IMPACT OF Ca DOPING ON THE STRUCTURAL CHARACTERISTICS OF La1-XCaXFe0.5Mn0.5O3

A series of perovskite compounds La1-xCaxFe0.5Mn0.5O3 (x = 0, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8 and 0.9) were synthesized using the conventional ceramic method. The influence of the Ca-doping on the crystal structure of these compounds was studied using was investigated through X-ray diffraction (XRD) and Raman scattering spectroscopy. XRD analysis revealed that all the samples crystallize in an orthorhombic structure with the Pbnm space group. The variation in lattice parameters, bond lengths and bond angles created by the difference in valence state and ion size due to the Ca-doping leads to the distortion and tilt of octahedra in the samples.

Improved cycle capability of Mn-doped Fe2TiO5 anode for lithium-ion batteries

Good cycling stability and high theoretical capacity are provided by Fe2TiO5 (iron titanate) as an electrode material due to its distinct crystal structure and numerous redox couples. The conventional ceramic method successfully and effectively synthesises the material. This study discloses the successful doping and replacement of Ti4+ with Mn4+ in the unit cell of Fe2TiO5 pseudobrookite, resulting in decreased band gap energy and a regular increase in unit cell volume with increased Mn-concentration. Doping improves the overall electrical conductivity due to a higher ratio of Ti3+ to Ti4+ which ultimately boosts the electrochemical performance as an anode in LIBs application. The Fe2Ti1-xMnxO5 (x = 0.2) achieves a high specific surface area of 338.6 m2 g−1 with an average pore size distribution of ∼10 nm, which is beneficial to reduce the Li-ion diffusion path and provides large contact areas between electrolyte and electrode surface. The Fe2Ti1-xMnxO5 (x = 0.2) stays ahead in its electrochemical performance compared to all counter partners delivering 765.6 mAh g−1 of initial discharge capacity and having a capacity retention of 392.3 mAh g−1 after 100 continuous charge discharge cycles at a current density of 100 mA g−1. Additionally, an excellent rate performance of 327.9 mAh g−1 is observed even at 5000 mA g−1. No further capacity fading is noted for another 45 cycles, demonstrating the structural stability of electrode material at variable current densities. The superior electrochemical results of Mn4+ doped Fe2TiO5 manifestly show the possibility of serving as an electrode material for high-performance battery applications.

Sintering behaviors and microwave dielectric properties of Ba3P4O13 ceramics

In this study, a Ba3P4O13 ceramic was synthesized adopting a conventional solid-state ceramic method. Optimal microwave dielectric properties were obtained in ceramic samples sintered at 840 °C for 4 h with a εr (permittivity) = 7.9, a Q × f (Q = 1/dielectric loss, f = resonant frequency) = 14,200 GHz (at 11.18 GHz), and a τf (TCF, temperature coefficient of resonant frequency) = + 48 ppm/°C. τf value shifted from + 45 ppm/°C to ‒ 31.5 ppm/°C with sintering temperature rising from 860 °C to 900 °C, and this decrease in τf value was mainly caused by the decomposition of Ba3P4O13 into BaP2O6 and Ba2P2O7. Furthermore, a ceramic sample sintered at 890 °C achieved a near zero τf (− 1.3 ppm/°C), together with a εr = 7.7 and a Q × f = 13,000 GHz (at 11.44 GHz). Ba3P4O13 ceramic has demonstrated potential as a material suitable for low-temperature co-fired ceramic technology (LTCC).

Structural and electrical conduction properties of Y3+ ions substituted Li-Zn-Ti ferrites

Rare earth yttrium substituted lithium ferrites Li0.5Zn0.1Ti0.1Y x Fe2.3– x O4 with nominal composition x = 0.00 to 0.10 in steps of 0.02 was prepared by the conventional ceramic method. The samples were sintered at 1050 °C for 6 h using resistive conventional heating. X-ray diffraction (XRD) patterns confirmed the formation of a single phase with a spinel structure. FTIR studies also confirmed the tetrahedral and octahedral metal-oxygen bonding of the spinel structure. Structural parameters like density, lattice constant, and crystallite size, site distances, bond length distances were measured from XRD data. The crystallite size reduces while the density increased with the progressive substitution of Y3+ ions. The Fe3+ ions at the A and the B sites mainly contributes to the electromagnetic properties of ferrites. Y3+ ions preferably entering the B sites can significantly interfere with the conduction mechanism of lithium ferrites. The objective of the present work is to find out the effect of Y3+ substitution on the structural and electrical conduction response Li-Zn-Ti ferrites. The DC resistivity initially is found to increase for concentration x = 0.04 and then decrease with further substitution. The study of the temperature dependence of DC resistivity depicts two types of conduction mechanisms in the range studied. The results obtained are analyzed and presented in the paper.

Enhanced lithium storage performance derived from Fe2Ti1-xNixO5 (0 ≤ x ≤ 0.1) as a fast charging anode

Using iron titanate (Fe2TiO5) as an electrode provides high theoretical capacity and good cycling stability because of its multiple redox couples and unique crystal structure. The synthesis of the material is successfully carried out using the conventional ceramic method. The effect of Ni2+ substitution on the overall electrochemical performance of Fe2Ti1-xNixO5 anode material is explored. When Ni2+ replaces Ti4+ in the pseudobrookite Fe2TiO5 unit cell, the volume increases smoothly with the amount of nickel and the electrical conductivity is enhanced because of the higher Ti3+/Ti4+ ratio. With pore sizes of around 10 nm and specific surface areas of 330.81 m2 g−1, Fe2Ti1-xNixO5 can provide large contact areas between the electrode and electrolyte and shorten the lithium-ion diffusion distance. With discharge capacities of 368.6 mAh g−1 at the 100th cycle, Fe2Ti1-xNixO5 negative electrode exhibits outstanding electrochemical performance. Furthermore, it demonstrates excellent rate stability, with a discharge capacity of 310.6 mAh g−1 at a current rate of 5000 mA g−1. Over another 45 cycles, a high discharge capacity of 367.1 mAh g−1 was maintained at a current density of 100 mA g−1 even after the rate performance test. The Ni2+ doping results in faster Li+ insertion/extraction kinetics due to reduced Li+ diffusion paths, which leads to performance improvement.

Structural, electronic, and optical properties of CaCoSi2O6 and Ca2CoSi2O7 blue pigments: A combined experimental, DFT+U, and BSE study

The exceptional characteristics of pigments, such as their high thermal stability, affordable production costs, and easy manufacturing procedures, are the reasons for their steady growth in industrial applications. On the other hand, the use of theoretical computations to forecast pigment color is a novel and significant area of study. In this study, CaCoSi2O6 (co-pyroxene) and Ca2CoSi2O7 (co-akermanite) pigments were synthesized using a conventional ceramic method. We studied the structural, magnetic, electronic, optical, and colorimetric properties of the pigments within experimental and theoretical approaches. The structural characteristics of the pigments were investigated by X-ray diffraction technique (XRD), Scanning Electron Microscope (SEM), UV–visible (UV–Vis) spectroscopy, and color measurement (CIE L*a*b*) colorimetry methods. Also, Hubbard Density Functional Theory (DFT + U) calculations were performed using 40 atoms of co-pyroxene and 24 atoms of co-akermanite. We employed the Bethe-Salpeter equation (BSE) method for studying the absorption spectrum and color of pigment samples. The theoretical energy gap values for the CaCoSi2O6 and Ca2CoSi2O7 structures were determined to be 4.2eV and 3.5eV, respectively. While the direct experimental band gap for CaCoSi2O6 and Ca2CoSi2O7 is about 4eV and 3.9eV, respectively. Comparing the outcomes, it can be inferred that the BSE method represents a valuable approach to predicting the absorption spectra and color features of pigment structures.

Vat photopolymerization 3D printing of polymer-derived SiOC ceramics with high precision and high strength

Polymer-derived ceramic (PDC) combined with 3D printing technology allows for the fabrication of various complex 3D structures and components that cannot be achieved through conventional ceramic preparation methods. However, current 3D printing PDC technologies suffer from low accuracy, poor mechanical and low ceramic yield, which severely limit their application values. Here, we report a polysiloxane-based preceramic polymer (PCP) precursor capable of producing high-precision and high-strength SiOC ceramics with ceramic yield as high as 56.9% after pyrolysis at 1100℃ in vacuum. Adding butyl acrylate into the precursor significantly improves printing resolution. Through special material design and printing parameter optimization, we fabricate various complex structures with overall sizes ranging from submillimeters to centimeters and printing resolution as high as 5 μm via vat photopolymerization 3D printing. The compressive strength of SiOC ceramic with I-WP structure reaches up to 240MPa while its density is only 0.367g/cm3, corresponding to a specific strength as high as 6.54 × 105N·m/kg. The printing resolution, specific strength and ceramic yield are all at the top level compared with previously reported works. The proposed approach will greatly promote the industrial application of 3D printing PDC technology in engineering fields and extreme environments.

Short Review of Flash Sintering: Mechanisms, Microstructures, and Mechanical Properties

This review article highlights the potential of flash sintering as a novel densification technology for advanced ceramics. Conventional ceramic sintering methods involve heating a powder compact at high temperatures for several hours to trigger the solid-state diffusion of atoms. In contrast, flash sintering takes advantage of electric field and current to drastically lower processing time and temperature, providing a promising solution to reduce the economic, energetic, and environmental costs associated with traditional ceramic sintering methods. The effects of electric field and current during flash sintering result in unique non-equilibrium microstructures that enhance the mechanical properties of advanced ceramics through defect-mediated inelastic deformation mechanisms. This article provides an overview of the flash sintering mechanisms, the unique microstructural features observed in flash-sintered ceramics, and their impacts on mechanical properties.

Magnetic properties of Mn/Co substituted nano and bulk Ni–Zn ferrites: A comparative study

The present work shows the comparative studies on the magnetic properties of Ni0.4Zn0.6-xCoxFe2O4, (Ni–Zn–Co) and Ni0.4Zn0.6-xMnxFe2O4 (Ni–Zn–Mn) with x = 0.00 to 0.25 in steps of 0.05, ferrites synthesized by sol-gel autocombustion and conventional ceramic methods. Rietveld refinement data confirms the formation of single phase - spinel crystal structure in all the samples. The role of ferromagnetic dopants like Co and Mn on the structural, microstructural, magnetic characteristics such as Curie temperature (Tc), saturation magnetization and coercivity of NiZnFe2O4 ferrite are investigated. The influences of crystallite size obtained by using two different synthesis methods on different magnetic properties are highlighted. Continuous Tc increases have been noticed in both instances along with increasing dopant concentrations. However, compared to Ni–Zn–Mn ferrites, Ni–Zn–Co ferrites display greater Tc values. The experimental observed magnetic moments measured from vibrating sample magnetometer (VSM) are fitted with the theoretical data. The saturation magnetization values exhibit a marginal increase in the bulk form of the material as compared to its nanocrystalline counterparts. On the basis of distribution of cation and exchange interactions between magnetic cations at its tetrahedral and octahedral sublattices, the typical mechanisms accountable for the observed trends were elucidated. In addition, the dc-resistivity and dielectric loss are measured to show the application aspects of the materials in various potential device applications.

Magnetic Studies of Nanocomposites of La-Substituted Bismuth Ferrite and Zn-Substituted Lithium Ferrite

La-substituted BiFeO3 and Zn-substituted Li0.5Fe2.5O4 (LZFO) were synthesized by sol-gel and auto-combustion techniques, respectively. Nanocomposites of these two phases were prepared using the conventional ceramic method. They were pressed into pellets at an applied pressure of 100 kg wt/cm2 and sintered at 600 °C. The presence of the two phases in the synthesized nanocomposites was confirmed from selected area electron diffraction spectra using transmission electron microscope in conjunction with X-ray diffraction spectra. The morphology and magnetic properties of the sintered nanocomposites were investigated. The morphology of the sintered nanocomposites was analyzed using scanning electron microscope, and the particle sizes varied from 316 to 106 nm with increasing LZFO content. Transmission electron microscopy images give the grain size data of the sintered nanocomposites. Magnetic properties of the sintered nanocomposites were studied as a function of LZFO content using a M–H hysteresis curve. The possible mechanisms for the obtained results are discussed.

In Vitro Degradation of Mg-Doped ZrO2 Bioceramics at the Interface with Xerostom® Saliva Substitute Gel

Zirconia-based bioceramics, one of the most important materials used for dental applications, have been intensively studied in recent years due to their excellent mechanical resistance and chemical inertness in the mouth. In this work, the structural, morphological and dissolution properties of the Zr1-xMgxO2 (x = 0.05, 0.1, 0.15, 0.2, 0.25, and 0.3) system, prepared by the conventional ceramic method, were evaluated before and after immersion in saliva substitute gel (Xerostom®, Biocosmetics Laboratories, Madrid, Spain), one of the most common topical dry mouth products used in dentistry. The X-ray powder diffraction (XRPD), Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy/energy-dispersive X-ray spectroscopy (SEM/EDS) techniques were employed to investigate the phase transformations and morphology of the ceramics during the degradation process in Xerostom®. In vitro analyses showed overall good stability in the Xerostom® environment, except for the x = 0.05 composition, where significant t- to m-ZrO2 transformation occurred. In addition, the strong interconnection of the grains was maintained after immersion, which could allow a high mechanical strength of the ceramics to be obtained.

Microwave dielectric properties of MnTeMoO6 ceramic and lowering its dielectric loss by using Mg-substitution in the A-site

The MnTeMoO6 (MTMO) ceramics were prepared by the conventional solid-state ceramic method. It exhibits an orthorhombic structure, belongs to the space group P21212(18) and possesses a favorable combination of dielectric properties (εr =12.3, Q×f =36,000 GHz, and τf =–63 ppm/°C) at microwave frequency. The effects of A-site Mg-substitution on the sintering behavior, phase evolution, and microwave dielectric properties of MTMO ceramics were also investigated. XRD analysis showed that all samples reveal MTMO phase indicating the formation of solid solution in the experimental range. Upon substituting 5 mol. % Mg in the A-site, the relative density of the specimen can be raised from 95.1 % to 97.3 % along with the optimized properties of εr = 13, Q×f = 56,000 GHz and τf = –58.2 ppm/°C, which reveals a 55 % enhancement in the Q×f of the MTMO ceramic. It also renders an excellent chemical compatibility with aluminum metal electrode suggesting that it is a potential candidate for ULTCC applications.

The influence of sintering condition on microstructure, phase composition, and electrochemical performance of the scandia-ceria-Co-doped zirconia for SOFCs

Samples of 6 mol% Sc2O3 - 1 mol% CeO2 co-doped ZrO2 were fabricated by conventional ceramic processing methods and sintered at various temperatures from 1000 to 1650?C in air. The sintering conditions on microstructure and phase content are investigated using various characterization methods, including pycnometry, diffraction, and spectroscopy. The electrical conductivity of samples was investigated using electrochemical impedance spectroscopy (EIS). The effect of inductive load (measured from room temperature to 800?C) is discussed in low to high temperature regimes. At T<400?C since the arc is not a complete semicircle, the high-frequency arc could be fit using a constant phase element (CPE), while by subtraction of inductive load, a good fit is achieved using a capacitor element instead of CPE. The Arrhenius conductivity plot of samples reveals that the specimen sintered at 1600?C for 6 hours exhibits the highest conductivity. The activation energy (Ea) and conductivity preexponential (?0) factor are calculated from a linear fit to data that decreases by the increase in sintering temperature.

Investigation The Effect of Particle Size and Annealing on the Performance of Nano/Micro Sized ZnO-Based Varistors

In this study, the influence of different ZnO particle sizes and the oxygen annealing process on the microstructure, and electrical properties of ZnO-based varistors was investigated. ZnO-Bi2O3-Mn2O3 discs based varistors with different size of ZnO particles were prepared by conventional ceramic method. Then half of varistors discs were annealed in oxygen atmosphere at 700 °C. SEM, Raman spectroscopy, and current-voltage (I–V) measurement were used. The results showed a significant improvement in distribution and growth of grain sizes in nano-size samples compared to that of micro-size samples. The electrical properties including nonlinear coefficient and breakdown voltage improved to 49 and 2555 V in nano-size compared with 32.5 and 201V in micro-size.

Ferrite materials with high saturation magnetic induction intensity and high permeability for magnetic field energy harvesting: Magnetization mechanism and Brillouin function temperature characteristics

Manganese-zinc (MnZn) ferrites play an indispensable role in energy transform and harvesting. It is notable to mention that the combined enhancement of initial permeability (μi), saturation magnetic induction (Bs) and Curie temperature (Tc) is conducive to improving the output power and safety of magnetic field energy harvesting devices. In this paper, high permeability MnZn ferrites were synthesized by a conventional oxide ceramic method. The thermomagnetic curves of MnZn ferrites were fitted according to the Néel molecular field theory (NMFT) and the Brillouin function. Then the molecular field coefficient γaa, γab, γbb, and Tc were calculated. Aiming at the magnetization mechanism of permeability, the contributions of domain wall motion and spin rotation were analyzed by fitting the complex permeability spectrum. Furthermore, the temperature characteristics of μi and Bs are analyzed, and we simulated and compared the effect of different magnetic properties of MnZn ferrites on the output of non-invasive magnetic field harvester. The MnZn ferrites with superior comprehensive performance own potential applications for non-invasive magnetic field harvester.

Sol—gel approach to low-temperature synthesis of single-phase metastable La2Ga3O7.5 melilite with enhanced grain-boundary oxide ionic conductivity via a kinetically favorable mechanism

Starting with the stoichiometric and highly homogeneous gel-precursor, single-phase metastable melilite La2Ga3O7.5, as the end-member of solid solution La1+xSr1−xGa3O7+x/2 (0≼x≼1), has been synthesized by solid-state reaction at 700 °C for 2 h via a kinetically favorable mechanism and characterized by X-ray diffraction (XRD), Raman, X-ray photoelectron spectroscopy (XPS), field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), AC impedance spectroscopy, etc. It has been revealed that the as-synthesized melilite La2Ga3O7.5 shows an orthorhombic symmetry with crystal cell parameters a = 11.4690(1) Å, b = 11.2825(4) Å, and c = 10.3735(4) Å, while has more Raman active modes than LaSrGa3O7 with a tetragonal structure, which was also synthesized under the same conditions for comparison, but tends to slowly decompose into perovskite LaGaO3 and Ga2O3 when annealed at 700 °C for over 20 h driven by its meta-stability. Moreover, the metastable La2Ga3O7.5 shows a higher XPS binding energy for the excess oxide ions in the crystal structure than those at normal lattice sites. Its intrinsic grain oxide ion conductivity can reach as high as 0.04 and 0.51 mS·cm−1 at 550 and 700 °C, respectively, characterized by a simple Arrhenius relationship ln(σT)—1/T with invariable activation energy, Ea = 1.22 eV, over the temperature range from 300 to 700 °C, along with an apparent grain boundary conductivity that is about double that from the grains thanks to the clean grain boundaries. This paper provides a new strategic approach to the synthesis of complex oxides that may be of high performance but are difficultly achieved by the conventional ceramic method at high temperatures.

Obtaining and Characterizing the Pb(Mg1/3Nb2/3)O3–Ln(Mg1/2Ti1/2)O3 Doped System

Abstract The Pb(Mg1/3Nb2/3)O3-based ceramic system was obtained by using a modified variant of the conventional ceramic method in order to get pyrochlore-free compositions. Solid solutions obtained from Pb(Mg1/3Nb2/3)O3 and Ln(Mg1/2Ti1/2)O3 with Ln = Y3+, La3+, Pr3+, Nd3+ and Sm3+, were synthesized using a 3-step columbite precursor method and appropriate milling and sintering conditions. The structural phases of all sintered compositions were investigated in detail. The X-ray diffraction results demonstrate that all the samples possess a perovskite structure. The influence of dopant on the incorporation degree in the solid solutions was studied. The dielectric constants at three frequencies were measured and the influence of the dopant on these values was discussed.

Enhanced ferroelectric properties in B-site Sn doped Pb0.9Mn0.1Zr0.52Ti0.48O3

Polycrystalline compounds of Sn substituted Pb0.9Mn0.1(Zr0.52Ti0.48)1-xSnx O3 (where x = 0.05,0.1) are synthesized by conventional ceramic method. Raman spectroscopy study reveals the tetragonal structure of Sn substituted samples. Impedance spectroscopic studies reveal the non-Debye kind of relaxation process in the material. Grain and grain contribution to the electrical conduction was observed. The observed P-E hysteresis confirmed the ferroelectric nature of all the samples. With the increase of Sn doping, Pr, Ps and Ec values also increased.

Improved coercivity of W- and M-type composite hexaferrites using two different synthesis routes

Two series of W- and M-type composite hexaferrites were synthetized using the conventional ceramic method in two different synthesis routes. In the first synthesis route, W- and M-type composite hexaferrites were formed by reaction in the pre-sintering stage. In the second synthesis route, W- and M-type composite hexaferrites were obtained by physically mixing W- and M-type hexaferrites in the second ball milling stage. The influence of M-type phase on the structure and magnetic properties of W-type hexaferrites synthesized in both synthesis routes are investigated in detail. For both synthesis routes, X-ray diffraction (XRD) patterns of all samples indicated crystallization of W- and M-type hexaferrites phase and scanning electron microscopy (SEM) measurements revealed hexagonal platelet-like grains. In the pre-sintering stage, the saturation magnetization (4πMs) of all samples ranged between 3.30 kG and 4.25 kG. The remanence ratio (Mr/Ms) changed from 0.77 to 0.88 with the increase of pre-sintering temperature. The coercivity (Hc) of all samples ranged between 456 Oe and 1846 Oe. The ferromagnetic resonance (FMR) linewidth (ΔH) ranged between 466 Oe and 748 Oe. In the second ball milling stage, 4πMs and Mr/Ms maintained a relatively stable value of ~4.5 kG and ~0.89, respectively. Hc increased from 519 Oe to 620 Oe with the increase of M-type hexaferrites. ΔH ranged between 317 Oe and 573 Oe. We note that in both synthesis routes only the composite hexaferrites synthesized in the pre-sintering stage have a significantly improved coercivity from 456 Oe to 1846 Oe. This enhancement in coercivity is attributed mainly to the effect of exchange coupling among ferrite grains. In addition, the ΔH decreases with the addition of M-type hexaferrites.