Standard Ceramic Technique Research Articles

Tailored Synergy: Synthesis and In-Depth Structural Analysis of x[Ni0.2Cu0.3Co0.5Fe2O4] + (1-x)[Ba0.7Sr0.3TiO3] Composites

M E Composites with composition x[Ni0.2 Cu0.3 CO0.5 Fe2 O4 ] + (1-x)[Ba0.7Sr0.3TiO3 ], Where x varying from 0.1 to 0.4 in molar ratio, were prepared by standard double sintering ceramic technique. The presence of ferrites phase, namely [Ni0.2 Cu0.3 CO0.5 Fe2 O4 ] and ferroelectric phase, namely [Ba0.7Sr0.3TiO3 ], were confirmed by X-Ray Diffraction analysis, whereas SEM micrographs were obtained to study the morphology of samples. The x ray diffraction patterns exhibit a set of well-defined ferrites and ferroelectric peaks. The tetragonality ratio c/a, of the ferroelectric phase remains the same in all the samples, the porosity varies from 20% to30% while the average grain diameter lies in the range of 0.5µm to 2 µm.

Ionic (O2– and H+) Transport in Oxygen-Deficient Perovskites La2Me+3ZnO5.5

The paper is devoted to the study of the conduction mechanism in perovskite phases with composition La2Me+3ZnO5.5 (Me+3 = Al3+, Sc3+, In3+). The phases were synthesized by a standard ceramic technique in the 700–1300°C temperature range. The structure of the La2InZnO5.5 and La2ScZnO5.5 samples is orthorhombic, while the La2AlZnO5.5 sample crystallizes in the cubic symmetry. The electrical conductivity of La2Me+3ZnO5.5 (Me+3 = Al3+, Sc3+, In3+) samples is studied as a function of temperature (200–900°C), oxygen partial pressure pO2, and humidity pH2O. The complex oxides are found to have a mixed type of conduction in air, the electronic contribution (the p-type conduction) increases with increasing temperature. The phases exhibit the dominant oxygen-ion transport at temperatures below 500°C. In wet atmosphere, Sc3+- and In3+-containing samples are capable of incorporating water from gas phase and forming proton defects. No significant proton transport in the La2AlZnO5.5 sample is realized. The partial conductivities σH+, σO2−, σh in a wide range of temperatures and рО2 are discussed.

Silane Heat Treatment Could Eliminate the Hydrofluoric Acid Etching of Lithium Disilicate Overlays: A Four-Year Follow-Up

A four-year follow-up of a novel silane heat treatment method for bonding lithium disilicate overlays to tooth structures without hydrofluoric acid etching of the ceramic surface is presented in this case report. Silane heat treatment modifies the silane layer and thus enhances resin ceramic bond strength without hydrofluoric acid etching. The standard ceramic preparation technique prior to bonding silicate ceramics to tooth structure is hydrofluoric acid etching and applying a silane coupling agent, followed by dental adhesive. In this case, the micromechanical roughening of the ceramic surface was performed by air abrasion with Al2O3. Silane heat treatment with constant 120°C airflow, applied for 60 sec, followed by dental adhesive application enhanced the resin-ceramic bond strength. After a four-year follow-up, the restorations' clinical appearance could be defined as excellent/very good according to the FDI clinical criteria for the evaluation of direct and indirect restorations. This clinical result supports many in vitro studies regarding the resin-ceramic bond strength and durability obtained through postsilanization heat treatment.

Resistivity and magnetization bimodal improvement in Ni ferrite nanoparticles by Mg substitution

Ferrites are still attracting the interest of researchers as well as achieving large sales worldwide owing to the large number of utilizations in a variety of products. In this work, a series of Mg-doped Ni ferrites, namely Ni1-xMgxFe2O4, were produced using standard ceramic technique as it is mostly used in commercial production of ferrites. All compositions are crystallized in spinel form and reveals single-phase cubic spinel structure. From FT-IR spectra of the samples, the spectral frequencies of the vibrational bands of different Mg concentration are reported. The IR spectral analysis of the investigated samples assured the formation of spinel structure. The magnetic susceptibility was reported as function of temperature. The Curie temperature was increased slightly as well as the susceptibility up to x = 0.4. The resistivity was improved as a result of Mg doping. At x = 0.4, the enlargement in the resistivity reached 97% with 40% Mg2+ on the expense of Ni2+ with an observable enhancement of the magnetic susceptibility values and a shift of the Curie point towards higher values.

Effects of Interdomain and Intradomain Pores of Cu-Zn Ferrite Substituted with Nd Investigated Using Positron Annihilation Lifetime Technique

Positron annihilation lifetime spectroscopy at room temperature is used to investigate polycrystalline Cu-Zn ferrite samples substituted with Nd. Standard ceramic technique is used to prepare all investigated samples. The variation of positron annihilation parameters I1%, I2%, τ1, and τ2 are demonstrated with grain size, initial permeability, homogeneity of the samples, and electrical resistivity with Nd concentration. The important novel points are: (1) Intragranular pores are equal to the sum of intra- and interdomain pores. The lifetime τ1 is increased due to the decrease of the intradomain pores. The initial permeability and homogeneity are decreased with increasing the interdomain pores. The electrical resistivity is increased due to the increase of the interdomain pores.

Synthesis of zinc substituted cobalt ferrites via standard double sintering ceramic technique: A study on their structural, magnetic and dielectric properties

Synthesis of zinc substituted cobalt ferrites via standard double sintering ceramic technique: A study on their structural, magnetic and dielectric properties

Variation of Particle Size with Copper Content in Copper Cobalt Ferrite

AbstractNanoparticle size polycrystalline aluminium substituted copper cobalt ferrite samples CuxCo1‐xFe2‐2yAl2yO4 (where x = 0.0, 0.2, 0.4, 0.6, 0.8, 1.0; y = 0.05, 0.15, and 0.25) have been prepared by standard ceramic technique. The effects of aluminium and copper on structural properties of cobalt ferrite are studied. A universal testing machine as well as Archimedes’ method is applied for determining the physical properties of the samples. Phase formation is investigated using x‐ray diffraction, infrared absorption technique, and scanning electron microscope technique. The size of particle raises with the increase in concentration of Al3+ content. The particle size occurs in the nano range 50–100 nm. The particle size is a very important parameter in terms of ferrite.

Thermodynamics of BaCa(1 + y)/3Nb(2 − y)/3O3 − δ·xH2O proton-conducting perovskites

Complex perovskites BaCa(1 + y)/3Nb(2 − y)/3O3 − δ (y = 0, 0.18 and 0.5) with 1:1-ordered structure ( $$ Fm\bar{3}m $$ space group) were synthesized by standard ceramic technique. The enthalpy increments for these oxides were measured in the temperature range of (295–1273) K by drop calorimetry, and experimental points were fitted with an integral of a single Einstein term. The hydration enthalpies for BaCa(1.18)/3Nb(1.82)/3O2.91 (BCN18), directly measured by calorimetry, were found to be equal to (− 86.7 ± 4.2) kJ (mol H2O)−1 and (− 88.8 ± 4.0) kJ (mol H2O)−1 at (673.8 ± 0.8) K and (872.8 ± 1.1) K, respectively. The calorimetrically determined enthalpies of hydration were found to be in agreement with those calculated using water vapor pressure–temperature–composition data. The increase in the off-stoichiometry index y in BaCa(1 + y)/3Nb(2 − y)/3O3 − δ leads to more exothermic hydration heats. The enthalpies of formation from elements, determined by drop solution calorimetry for dehydrated BaCa(1 + y)/3Nb(2 − y)/3O3 − δ with y = 0, 0.18 and 0.5, become less exothermic with increasing calcium content, and are equal to (− 1577.5 ± 14.5) kJ mol−1, (− 1533.6 ± 14.8) kJ mol−1 and (− 1492.2 ± 14.6) kJ mol−1, respectively. The thermodynamic data obtained allow calculating the enthalpies of formation and enthalpy increments for BaCa(1 + y)/3Nb(2 − y)/3O3 − δ with arbitrary water content.

Phase formation processes and synthesis of solid solutions in Ca-R-Nb-M-O systems

During the study of the phase formation process in Ca-R-Nb-M-O systems (R=La, Bi, M=Mo, W), an attempt was made to obtain single-phase compounds of CaRNbMO8 composition by the standard ceramic technique. In addition, samples based on LaNbO4, CaWO4, BiNbO4 were also synthesized by the standard ceramic technique. The phase composition of the samples was studied by XRD analysis. The electrical conductivity of the obtained solid solutions and potential composite materials was investigated by impedance spectroscopy.

Mechanical behavior, enhanced dc resistivity, energy band gap and high temperature magnetic properties of Y-substituted Mg–Zn ferrites

We report the synthesis of Y-substituted Mg–Zn [Mg0.5Zn0.5Y x Fe2−x O4 (0 ≤ x ≤ 0.05)] ferrites using conventional standard ceramic technique. The samples were characterized by x-ray diffraction (XRD) analysis, field emission scanning electron microscopy (FESEM), FTIR spectroscopy, UV–Vis spectroscopy and quantum design physical properties measurement system (PPMS). XRD patterns confirm the single phase cubic spinel structure up to x = 0.03 and appearance of a secondary phase of YFeO3 for higher Y contents. FESEM images depict the distribution of grains and EDS spectra confirmed the absence of any unwanted element. Completion of solid state reaction and formation of spinel structure has been revealed from FTIR spectra. The FTIR data along with lattice constant, bulk density and porosity were further used to calculate the stiffness constant (C ij), elastic constant and Debye temperatures. Mechanical stability of all studied compositions is confirmed from C ij using Born stability conditions. Brittleness and isotropic nature are also confirmed using Poisson’s ratio and anisotropy constants, respectively. The enhancement of dc electrical resistivity (105Ω cm to 106Ω cm) with Y content is observed. The energy band gap (increased with Y contents) is found in good agreement with dc electrical resistivity. Ferrimagnetic to paramagnetic phase change has been observed from the field dependent high temperature magnetization curves. The magnetic moments and saturation magnetization were found to be decreased with increasing temperature. The Curie temperature (Tc) has been measured from temperature dependent magnetic moment (M-T) and initial permeability (μ′i-T) measurements and found to be in good agreement with each other. Decrease in Tc with Y content is due to redistribution of cations and weakening of the exchange coupling constant. The magnetic phase transition has been analyzed by Arrott plot and found to have second order phase transition. The dc resistivity endorses the prepared ferrites are suitable for high frequency and high temperature magnetic device applications as well.

Phase Transition (Spinel-Ortho) Ferrite Doped with Holmium

A series of perovskite type oxides with formula La1-xHoxFeO3, with Ho substitute for La, where (x = 0.1, 0.2, 0.3 and 0.4). The samples have been prepared by the standard ceramic technique, sintered at 1200˚C for nine hours. Their crystalline structure was investigated using X-ray diffraction and IR spectroscopy. The X-ray diffraction analysis illustrates that the system La1-xHoxFeO3 has a perovskite orthorhombic phase. IR absorption spectra of La1-xHoxFeO3 showed two main characteristic absorption bands in the far infrared region. These bands are assigned to oxygen octahedral bending vibration and oxygen tetrahedron stretching vibration. It was found that the DC electrical conductivity increases linearly with temperature ensuring the semiconducting nature of the samples. The dielectric properties, Electron Spin Resonance (ESR) spectra, and thermal properties have been studied, to go through the material and explore its ability to be used for many industrial applications.

Physical and spectral studies of Mg-Zn ferrite prepared by different methods

Nano particle of Magnesium Zinc ferrite (Mg1-xZnxFe2O4, where x = 0, 0.1, 0.2, 0.3, 0.4 and 0.5) have been prepared by using the standard ceramic technique and mechanical ball milling method. X-ray diffraction (XRD), (IR) spectra, and scanning electron microscope (SEM)were carried out to characterize the prepared samples. Single phase cubic spinel structure with a main peak (311) at 2Ɵ = 34o was observed for all studied samples. The crystallite size was found to be within the range 37–65 nm. From IR spectra, the absorption bands at 605 cm-1 (ν1) and 435 cm-1 (ν2) were observed and are assigned to tetrahedral (A site) and octahedral (B site) groups complex respectively. Morphological study which were determined by scanning electron microscopy (SEM) which shows grains agglomerated with different shapes and sizes. The initial permeability was measured at different frequencies. The fast decrease in initial permeability µi at Tc is a good reason to be a very strong candidate for magnetic switch devices.

Structural analysis and role of cation distribution on the magnetic properties of single phase Ni-doped copper chromium ferrite

A series of single-phase spinel structure was prepared by the standard ceramic technique in order to study the effect of cation doping on the microstructure and magnetic properties of spinel ferrite. We have used six Ni concentrations in the doping process of mixed spinel (Mg, Cu, Cr ferrite). Single-phase formation for all the prepared samples was confirmed using X-ray diffraction. Rietveled refinement was applied to study the structural characteristics and the cation distribution of the compounds. The refined data showed that the Mg cations have tetrahedral site preference, while Ni and Cr cations prefer the octahedral site. Hence replacing Ni cation by Mg cation forces the structure to be normal spinel. With increasing Ni content the unit cell dimension decreases and the degree of inversion increases. Accordingly the microstrain decreases, while the crystallite size tend to increase as Ni content increases. From the magnetic measurements it was found that, the magnetic susceptibility decreases with increasing temperature which revealed the normal behaviour of the spinel ferrite. The Curie temperature was found to increase with increasing the Ni content. The impressive results obtained were the decrease of the effective magnetic moment and the exchange interaction constant JBA with increasing Ni content. The results show that the magnetic nature of the doping element does not play a major role in determining the final magnetic properties of the compound. Instead, the cation distribution is the significant parameter.

Structural, magnetic and toxicity studies of ferrite particles employed as contrast agents for magnetic resonance imaging thermometry

We carried out comprehensive structural, magnetic and toxicity studies of Mg1−xZnxFe2O4 and Cu1−xZnxFe2O4 ferrites that we plan to use as contrast agents for magnetic resonance-imaging thermometry. Samples were prepared by a standard ceramic technique. Their structural properties were investigated with an x-ray diffraction system, and data was analyzed using the Rietveld method that allowed us to determine cations distribution. Magnetic properties of MgZn and CuZn ferrites were studied using a superconducting quantum interference device magnetometer, a vibrating sample magnetometer, and Mössbauer spectrometer. Magnetometry measurements were cross-correlated with XRD results and compared with magnetic properties determined by Mössbauer spectroscopy, allowing us to understand the magnetic structure of studied ferrites. The temperature dependent magnetic measurements were used as guidance to select the most suitable MgZn and CuZn ferrites compositions for MRI thermometry near human body temperature. The inflammation studies indicated that MgZn ferrites are more suitable from the toxicology point of view for MRI thermometry.

Probing the local atomic structure in CoLa0.15Fe1.85O4 as a function of the synthesis method by multi edge XAFS

We combined x-ray powder diffraction (XRD) and x-ray absorption fine structure spectroscopy (XAFS) to characterize the crystallographic and local atomic structure of nanosized La3+ substituted CoFe2O4 spinel ferrite of composition CoLa0.15Fe1.85O4 synthesized by different synthesis routes: standard ceramic technique, citric acid (citrate) precursor and urea assisted flash auto-combustion process. Rietveld refinement of XRD patterns allowed to describe the long-range atomic structure that was used as structural model for quantitative analysis of XAFS spectra collected at the Fe–K, Co–K and La–L3 and refined via a multi-edge approach, which provided details about local atomic structure and coordination chemistry around the absorbers. Combining the complementary information from XRD and XAFS it was possible to reliably describe the cation distribution over the two spinel sublattices (tetrahedral and octahedral) as a function of the synthesis routes. We demonstrated that the inversion parameter, the cation distribution, and the local atomic structure depend strongly on the synthesis method which in particular affects the La3+ lattice-site and vacancies. In particular the citrate synthesis appears to provide a pure single pure phase with highest coordination number of La and lowest inversion parameter.

Study of physical properties towards optimizing sintering temperature of Y-substituted Mg-Zn ferrites

Optimum sintering temperature (Ts) plays an important role in controlling densification and growth of grains which greatly affect the magnetic and electrical properties of polycrystalline materials. Y-substituted Mg-Zn [Mg0.5Zn0.5YxFe2−xO4 (0 ≤ x ≤ 0.05)] ferrites have been prepared by using conventional standard ceramic technique and were sintered between 1100 and 1300 °C in the steps of 50 °C. Characterizations of the samples have been done by X-ray diffraction (XRD) technique, field emission scanning electron microscopy (FESEM), dielectric and permeability measurements to find the suitable Ts. XRD data have been analyzed and the results confirmed the same information regarding phase analysis at different Ts. Further characterization of the samples, sintered at 1100 and 1150 °C, were not continued due to their low density and high porosity. FESEM images indicate the change in microstructure with Ts. The decrease (increase) of ac electrical resistivity with Ts (Y content) has been observed while the dielectric constant behaves in opposite manner. Impedance spectroscopy also exhibited similar trend as ac electrical resistivity. The initial permeability revealed the wide stability zone of frequency and different optimum Ts for different compositions. The ac resistivity values for the compositions have been found higher at 1200 °C, but the compositions have highest value of bulk density and permeability at other Ts. The effect of Ts on the physical properties (bulk density, porosity and permeability) of Y-substituted Mg0.5Zn0.5YxFe2−xO4 (0 ≤ x ≤ 0.05) ferrites elucidate that the optimum Ts should be of 1250 °C for x = 0.01, 0.02 and 0.03 while the Ts should be of 1300 °C for x = 0.04 and 0.05.

Structural, electric and magnetic properties of (BaFe11.9Al0.1O19)1-x - (BaTiO3)x composites

This paper described to the ceramics (inorganic) two-component composites with controllable magnetic and electrical properties. Ceramic composite samples were produced via solid state reaction method (standard ceramic technique) from initial magnetic (BaFe11.9Al0.1O19 or BF) and ferroelectric (BaTiO3 or BT) phases. BT and BF initial compounds were mixed in stoichiometric ratios (BF)1-x - (BT)x (x = 0, 0.25, 0.5, 0.75 and 1) and sintered. Initial compounds BaFe11.9Al0.1O19 (x = 0) and BaTiO3 (x = 1) were also produced via standard ceramic technique. The constituent materials were chosen considering their perspective ferrimagnetic and ferroelectric properties, respectively for BF and BT. Moreover, Ba-hexaferrites are reported to exhibit ferroelectricity at room temperature as well, and the combination of two ferroelectric phases is of interest. Systematic investigations of the structural, magnetic and electrical properties versus chemical composition (x) were performed. As structural properties we have defined the features of crystal structure (a and c lattice parameters, volume of unit cell) and peculiarities of microstructure (density, porosity, average grain size). The ferrimagnetic phase transition temperature is almost independent of the content of BT, which is determined by the exchange interactions Fe3+-O2--Fe3+in the magnetic phase. However, the coercivity of composite samples is lower which is due to the contribution of the microstructure dependent shape-anisotropy to the total magnetic anisotropy energy. The permittivity vs. temperature behavior confirmed the existence of two ferroelectric phase transitions corresponding to structural phase transitions in BT (at about 400 K) and BF (at about 700 K). It was observed that the electrical properties of composite samples, including the temperatures of the phase transitions, critically depended on concentration x which affects the composite microstructure. This behavior was discussed in terms of microstructure analysis (grain size, porosity and density).

Yttrium-substituted Mg–Zn ferrites: correlation of physical properties with Yttrium content

Yttrium- (Y) substituted Mg–Zn ferrites with the compositions of Mg0.5Zn0.5YxFe2−xO4 (0 ≤ x ≤ 0.05) have been synthesized by conventional standard ceramic technique. The effect of Y3+ substitution on the structural, electrical, dielectric and magnetic properties of Mg–Zn ferrites has been studied. The single phase of spinel structure with a very tiny secondary phase of YFeO3 for higher Y contents has been detected. The theoretically estimated lattice constant has been compared with measured experimental lattice constant. The bulk density, X-ray density and porosity have been calculated. The Energy Dispersive X-ray Spectroscopy (EDS) study confirms the presence of Mg, Zn, Y, Fe and O ions in the prepared samples. Frequency dependence of conductivity has been studied and an increase in resistivity (an order) has been observed. Frequency dependence of dielectric constant ( $$\varepsilon$$ ), dielectric loss tangent ( $$\tan \delta$$ ) has been studied and the lowering of $$\varepsilon$$ with the increase of Y content was noted. Dielectric relaxation time was found to vary between 15 to 31 ns. The saturation magnetization (Ms), coercive field (Hc), remanent magnetization (Mr) and Bohr magneton (µB) have been calculated. The variation of Ms has been successfully explained with the variation of A–B interaction strength due to Y substitution. The soft ferromagnetic nature also confirmed from the values of Hc. The complex permeability has been studied and the initial permeability was found to increase with Y up to x = 0.01, thereafter it decreases. The values of electrical resistivity and dielectric constant with proper magnetic properties suggest the suitability of Y-substituted Mg–Zn ferrites in microwave device applications.

Negative Capacitance Effect in the Low-Frequency Impedance of Barium Strontium Titanate Semiconductor Ceramics

Polycrystalline (Ba0.85Sr0.15)0.999Ce0.001TiO3 samples prepared by a standard ceramic processing technique for positive temperature coefficient of resistance materials have been characterized by impedance spectroscopy. Major attention has been paid to the inductive character of the impedance in the low-frequency range of the measuring signal. In the literature, such an impedance is interpreted in terms of a negative capacitance effect. Based on analysis of the existing notions of the structure of grain boundaries in ceramics, we have proposed an equivalent circuit that models frequency dependences of the immitance in good agreement with experimental data.

Structural and electrical properties of CuLayFe2-yO4 ferrites


 
 
 
 Ferrite with the general formula CuLayFe2-yO4 (where y=0.02, 0.04, 0.06, 0.08 and 0.1), were prepared by standard ceramic technique. The main cubic spinel structure phase for all samples was confirmed by x-ray diffraction patterns with the appearance of small amount of secondary phases. The lattice parameter results were 8.285-8.348 Å. X-ray density increased with La addition and showed values between 5.5826 – 5.7461gm/cm3. The Atomic Force Microscopy (AFM) showed that the average grain size was decreasing with the increase in La concentration. The Hall coefficient was found to be positive. It demonstrates that the majority of charge carriers of p-type, suggesting that the mechanism of conduction is predominantly caused by hopping of holes. The resistivity was noticed to increase with the increase in La substitution. The activation energy Eav decreased with the frequency increase. The AC conductivity was found to increase with the frequency and La addition. Dielectric constant was noticed to decrease with frequency and La addition. The dielectric loss factor decreased with La content because rare earths are known as low dielectric loss materials.