Function Of Sintering Temperature Research Articles

High piezoelectric performance in lead-free (K, Na)NbO3 ceramics under a low driving field

In this work, lead-free (K0.485Na0.485Li0.03)Nb0.8Ta0.2O3 composition was designed to control the orthorhombic-tetragonal phases boundary near the room temperature as confirmed by Rietveld analysis, high-angle annular dark field scanning transmission electron microscopy, and temperature dependent dielectric constant. A comparative study of the direct and indirect synthesis methods was carried out and their functional properties were optimized as a function of sintering temperature (Ts) and dwell time. Here, we achieved a large dynamic piezoelectric constant (d33*) of 510 pm/V under a very low electric field of 15–30 kV/cm. Moreover, an enhanced static piezoelectric constant (d33) of 335 pC/N was obtained with a high Curie temperature (TC) of 315 °C. The large d33 and d33* simultaneously with high TC in a single composition are promising results in lead-free polycrystalline ceramics. The strategic design of this work opens a new door for the possible development of novel functional materials for device applications.

Understanding the Impact of Sintering Temperature on the Properties of Ni–BCZY Composite Anode for Protonic Ceramic Fuel Cell Application

Understanding the impact of sintering temperature on the physical and chemical properties of Ni-BaCe0.54Zr0.36Y0.1O3-δ (Ni-BCZY) composite anode is worthy of being investigated as this anode is the potential for protonic ceramic fuel cell (PCFC) application. Initially, NiO–BCZY composite powder with 50 wt% of NiO and 50 wt% of BCZY is prepared by the sol–gel method using citric acid as the chelating agent. Thermogravimetric analysis indicates that the optimum calcination temperature of the synthesised powder is 1100 °C. XRD result shows that the calcined powder exists as a single cubic phase without any secondary phase with the lattice parameter (a) of 4.332 Å. FESEM analysis confirms that the powder is homogeneous and uniform, with an average particle size of 51 ± 16 nm. The specific surface area of the calcined powder measured by the Brunauer–Emmett–Teller (BET) technique is 6.25 m2/g. The thickness, porosity, electrical conductivity and electrochemical performance of the screen-printed anode are measured as a function of sintering temperature (1200–1400 °C). The thickness of the sintered anodes after the reduction process decreases from 28.95 μm to 26.18 μm and their porosity also decreases from 33.98% to 26.93% when the sintering temperature increases from 1200 °C to 1400 °C. The electrical conductivities of the anodes sintered at 1200 °C, 1300 °C and 1400 °C are 443 S/cm, 633 S/cm and 1124 S/cm at 800 °C, respectively. Electrochemical studies showed that the anode sintered at 1400 °C shows the lowest area specific resistance (ASR) of 1.165 Ω cm2 under a humidified (3% H2O) gas mixture of H2 (10%) and N2 (90%) at 800 °C. Further improvement of the anode’s performance can be achieved by considering the properties of the screen-printing ink used for its preparation.

Understanding the oxygen reduction reaction of one-dimensional Ca3Co2O6 cathodes for SOFC

Understanding the processes of different cathode materials is part of the journey toward the development of intermediate-temperature solid oxide fuel cells. In this work, the one-dimensional Ca3Co2O6 (C326) electrode and its composite with Ce0.9Gd0.1O2-δ (CGO) are systematically investigated as a function of sintering temperature using a symmetrical cell test. For both batches of samples, the optimum sintering temperature is 1000 °C. Interpretation of the impedance spectra reveals that this optimization is associated with improvements in the processes of surface diffusion and interfacial charge transfer due to the higher effective reaction area for ionic transfer at the electrode/electrolyte interface and better connectivity between the electrode grains. The temperature dependence of the individual processes indicates that the addition of CGO significantly improves the steps of dissociative oxygen adsorption and diffusion, which should occur first on its surface, with the charge transfer of oxygen species at the CGO/C326 boundary being the rate-limiting step.

Evolution of crystallographic texture and grain boundary character in hot press sintered tungsten heavy alloy as a function of sintering temperature

Using the vacuum hot press sintering method, tungsten heavy alloys (93 W − 4.9Ni − 2.1Cu) was produced. The study explored the effect of sintering temperature on W-Ni-Cu heavy alloy. Studies in metallography reveals that an increase in sintering temperature led to the coalescence of tungsten grains and affected their mechanical, electrical properties. As a result, an alloy sintered at a high temperature (1450 °C) has the highest hardness (410 Hv0.5), electrical conductivity (19.72% of IACS), and relative density (96.6%).

Phase and structural evolution of zirconolite ceramics prepared by solid-state reaction sintering

The evolution of phase assemblage and microstructure of stoichiometric zirconolite (CaZrTi 2 O 7 ) ceramics, prepared by a solid-state reaction sintering route, was systematically investigated as a function of sintering temperature. Using powder XRD and quantitative phase analysis data, it was determined that the formation of zirconolite was a one-step reaction, without formation of intermediate phases. The accompanying fractions of secondary CaTiO 3 and ZrO 2 phases were reduced to approximately 2 wt % each after sintering at 1200 °C, with zirconolite formed as the major phase (> 99 wt%) after reaction at 1300 °C. Notable product densification only occurred at T ≥ 1400 °C, at which it was possible to achieve a relative density of 96.97% which is highly desirable for applications as a nuclear wasteform. The zirconolite-2M polytype structure (space group: C2/c) was formed in all products as expected, confirmed by combined high resolution TEM-ED analyses.

A new microwave dielectric ceramic Zn2V2O7 with low sintering temperature

A new microwave dielectric ceramic Zn 2 V 2 O 7 with low sintering temperature was synthesized. The Zn 2 V 2 O 7 exhibited a monoclinic structure with a densification temperature of 720 °C. The microwave dielectric properties , relative density, full width at half maximum (FWHM) of Raman spectra and packing fraction have been examined as a function of sintering temperature. Typically, the Zn 2 V 2 O 7 ceramic possessed optimum microwave dielectric properties of ε r = 9.67, Q × f = 23,968 GHz and τ f = -19.87 ppm/°C.

Sintering characteristics of plate-like bismuth titanate ceramics with preferred c - axis orientation for memory storage devices

Bismuth titanate (Bi4Ti3O12) (BIT) has been an attractive material due to its high Curie temperature, large remnant polarization and relatively low processing temperature, making it suitable for piezoelectric, pyroelectric and non-volatile random access memory storage devices. In this present work, polycrystalline textured bismuth titanate ceramics were synthesised by the cost-effective molten salt synthesis method. The effect of sintering conditions on the structural, morphological and dielectric properties have been carried out in detail. The X-ray diffraction studies reveal the formation of the monophasic structure of BIT ceramics with a preferential orientation along the c-axis. It is also noticed that the orientation along the c-axis increases with an increase in sintering temperature. Interestingly, the parameters like crystallite size and micro-strain calculated from the Williamson - Hall method could be tailored as a function of sintering temperature. The microstructural studies carried out using FESEM technique suggested the presence of plate-like morphology of BIT ceramics and subsequently, the elemental mapping analysis used to confirm the uniform distribution of the elements Bi, Ti and O present in the ceramic sample. The Fourier transform infrared and X-ray photoelectron spectroscopic studies have been done to identify the constituent chemical bonds and oxidation states of BIT ceramics. Interestingly, it is noted that the value of the dielectric constant increases with the increase in sintering temperature of BIT ceramics. Furthermore, the high dielectric constant value of 200 obtained at 100 kHz for 950 °C sintered sample could establish this material for the embedded capacitor in memory storage devices.

Sintering Temperature Driven Structural, Dielectric, Ferroelectric, and Piezoelectric Properties of 0.5Ba(Zr0.2Ti0.8)O3-0.5(Ba0.7Ca0.3)TiO3 Lead-Free Composites

Lead-free 0.5Ba(Zr0.2Ti0.8)O3-0.5(Ba0.7Ca0.3)TiO3 composites have been synthesized via sol-gel chemical route. We have systematically investigated the influence of sintering temperature on the structural and electrical properties of the BZT-BCT composites. The 0.5Ba(Zr0.2Ti0.8)O3-0.5(Ba0.7Ca0.3)TiO3 composites were prepared by combining Ba(Zr0.2Ti0.8)O3 (BZT) and (Ba0.7Ca0.3)TiO3 (BCT) powders and sintered at different temperatures 900-14000C. The electrical properties of BZT-BCT composites improve with increasing sintering temperature. The composites sintered at 1300 and 14000C exhibit enhanced ferroelectric properties with spontaneous polarization Ps ~ 11.2 μC/cm2 and 8.66 μC/cm2 respectively. The dielectric and piezoelectric properties of BZT-BCT composites also improve with increasing sintering temperature. The dielectric constant value εʹ ~ 2938, tan δ ~ 0.016 and piezoelectric co-efficient d33 ~ 278 pC/N were measured for BZT-BCT composite sintered at 14000C while observing a considerably high transition temperature of Tc ~ 1200C. The observed results are discussed in terms of structural and microstructural analysis as a function of sintering temperature.

Characterisation of the mechanisms taking place during liquid phase sintering of PM boron steels with the help of artificial intelligence

ABSTRACT Liquid phase sintering (LPS) of powder metallurgy (PM) components is a well-recognised strategy to enhance the densification of pressed-and-sintered compacts. This work reports the investigation on the liquid phase formation when a Fe–Ni–Mn–C–B master alloy (MA) is used as a boron carrier in combination with two iron base powders pre-alloyed with Mo. Through differential scanning calorimetry tests, quantitation of the microstructure with the help of artificial intelligence, as well as measurement of sintered density and strength as a function of sintering temperature, it was possible to unravel the mechanisms that take place before and during LPS. It was confirmed that a cascade of events takes place in the solid state prior to reaching the temperature necessary for a eutectic reaction to form a liquid. Additionally, the pre-alloyed Mo content was identified as a factor that modifies the initiation of LPS but not the LPS mechanisms per se.

The Effect of Heat Treatment of β-Tricalcium Phosphate-Containing Silica-Based Bioactive Aerogels on the Cellular Metabolism and Proliferation of MG63 Cells.

β-Tricalcium phosphate was combined with silica aerogel in composites prepared using the sol–gel technique and supercritical drying. The materials were used in this study to check their biological activity and bone regeneration potential with MG63 cell experiments. The composites were sintered in 100 °C steps in the range of 500–1000 °C. Their mechanical properties, porosities, and solubility were determined as a function of sintering temperature. Dissolution studies revealed that the released Ca-/P molar ratios appeared to be in the optimal range to support bone tissue induction. Cell viability, ALP activity, and type I collagen gene expression results all suggested that the sintering of the compound at approximately 700–800 °C as a scaffold could be more powerful in vivo to facilitate bone formation within a bone defect, compared to that documented previously by our research team. We did not observe any detrimental effect on cell viability. Both the alkaline phosphatase enzyme activity and the type I collagen gene expression were significantly higher compared with the control and the other aerogels heat-treated at different temperatures. The mesoporous silica-based aerogel composites containing β-tricalcium phosphate particles treated at temperatures lower than 1000 °C produced a positive effect on the osteoblastic activity of MG63 cells. An in vivo 6 month-long follow-up study of the mechanically strongest 1000 °C sample in rat calvaria experiments provided proof of a complete remodeling of the bone.

Lattice vibrational characteristics, crystal structures, and dielectric properties of LiMnPO4 microwave dielectric ceramics as a function of sintering temperature

LiMnPO4 (LMP) microwave dielectric ceramics were manufactured at different temperatures via a standard solid-state reaction method and the LMP ceramic sintered at 750 °C displayed dielectric properties of εr = 7.82 and Q × f = 29,189 (f = 12.7 GHz). The lattice vibrational characteristics of LMP ceramics were studied utilizing both infrared reflection and Raman scattering spectroscopy to clarify the basic principle of the dielectric response. The intrinsic properties that were fitted and simulated based on the infrared spectra agreed with the measured property values. The low-frequency vibrational modes contributed more to the dielectric properties than the high-frequency modes. Upon increasing the temperature, the permittivity was positively correlated with the bond length but showed the opposite trend of the Raman shift of mode 9 Ag(υ1). The Q × f value was positively correlated with the packing fraction but negatively correlated with the FWHM of mode 10 Ag(υ3). Thus, the structure–property relationships of LMP ceramics were established as a function of sintering temperature.

Electrical conductivity characteristics of Sr substituted layered perovskite cathode (SmBa0.5Sr0.5Co2O5+d) for intermediate temperature-operating solid oxide fuel cell

The high electrical conductivity of the cathode is one of the important factors for reducing the polarization resistance. For this reason, we here report the electrical conductivity characteristics of SmBa0.5Sr0.5Co2O5+δ (SBSCO) as a function of sintering temperature and current ranges. Calcined SBSCO samples were sintered at 1000, 1050, 1100, and 1150 °C. The current ranges applied in the process of measuring electrical conductivity were subdivided as 1.0A [0.05step], 0.5A [0.025step], and 0.1A [0.005step]. It was found that the sintering temperature affected the electrical conductivity in the following way: when the sintering temperature increases, an increase in the observed electrical conductivity is the result. However, as the current range decreases, it was found that the electrical conductivity would increase. The maximum and minimum conductivities of SBSCO sintered at 1150 °C were 2263S∙cm−1 at 50 °C and 382 S∙cm−1 at 900 °C with metallic behavior in air condition. When a current of 0.1A was applied to SBSCO sintered at 1150 °C, the electrical conductivity at the 800 °C was 1377.15 S/cm. It can be determined that the increase in the internal charge carrier flux of the SBSCO is associated with the decrease in the overall electrical conductivity of the Co-based metallic electrical conductivity. These results show that the high sintering temperature and low current range enable higher electrical conductivity at high operating temperature.

Sintering temperature influence on grains function distribution by neural network application

Artificial neural networks application in science and techonology begun during 20th century. This biophysical and biomimetic phenomena is based on extensive research which have led to understanding how neural as a living organism nerve system basic element processes signals by a simple algorithm. The input signals are massively parallel processed, and the output presents the superposition of all parallel processed signals. Artificial neural networks which are based on these principles are useful for solving various problems as pattern recognition, clustering, functional optimization. This research analyzed thermophysical parameters at samples based on Murata powders and consolidated by sintering process. Among different physical properties we applied out neural network approach on grain sizes distribution as a function of sintering temperature, T, (from 1190-1370?C). In this paper, we continue to apply neural networks to prognose structural and thermophysical parameters. For consolidation sintering process is very important to prognose and design many parameters but especially thermal like temperature, to avoid long and even wrong experiments which are wasting the time and materials and energy as well. By this artificial neural networks method we indeed provide the most efficient procedure in projecting the mentioned parameters and provide successful ceramics samples production. This is very helpful in prediction and designing the micro-structure parameters important for advance microelectronic further miniaturization development. This is a quite original novelty for real micro-structure projecting especially on the phenomena within the thin films coating around the grains what opens new prospective in advance fractal microelectronics.

Effect of sintering on the various properties of cobalt ferrite nanoparticles

Cobalt ferrite nanoparticles with the structural formula CoFe2O4 were synthesized by the auto-combustion method to investigate structural and dielectric properties. The synthesized sample were calcined at 600°C at the heating rate of 5°C/min using the conventional heating. The calcined sample were taken in five equal proportions and then given conventional sintering at different temperatures of 700°C, 800°C, 900°C, 1000°C and 1100°C separately for 4 h at the same heating rate. X-ray diffraction spectra were obtained using Bruker D8 Advance X-ray Diffractometer and they confirmed the phase formation of all the samples. From the X-ray diffraction data, lattice constant, average crystallite size and theoretical density were calculated. The experimental density and porosity were also found out for all the samples. FTIR and dielectric properties such as dielectric constant, dielectric loss and impedance were studied. From the IR spectra, various metal-oxide bonds present in the samples were studied. The dielectric constant and dielectric loss were studied as a function of sintering temperature and frequency. Dispersive behaviour is observed for the variation of dielectric constant and dielectric loss with frequency. The dielectric constant was found to be increasing with the increase in sintering temperature in high frequency region. Possible mechanisms contributing to all the obtained results were being discussed.

Original scientific paper examination of influence sintering temperature on mineral compounds

Mineral materials, such as corundum, quartz and periclase are very often used in technological processes. Due to its characteristics, and chemical reaction in solid state, these minerals form very interesting and useful material, cordierite. The mineral ratio in this compound (MgO : Al2O3 : SiO2) is 2:2:5. They form cordierite, electronic ceramic, which can be sintered in a narrow temperature range, at about 1375 °C. Composition of this electronic ceramics material is is 2MgO-2Al2O3-5SiO2 (MAS) and in this research 20% mass Bi2O3 was added in the aim of decrease the sintering temperature. The effects of sintering, the composition and morphology were followed by x-ray diffraction, scanning electron microscopy and EDS analysis, as a function of sintering temperature. MAS ceramics were sintered at 1000ºC, 1100ºC and 1200ºC.

Microstructure and mechanical properties of novel tungsten heavy alloys prepared using FeNiCoCrCu HEA as binder

In the present work, novel tungsten heavy alloys (WHAs) have been developed using FeNiCoCrCu high entropy alloy (HEA) as binder through conventional sintering process. The composition of the alloy is 90 wt% W-10 wt% HEA. FeNiCoCrCu HEA was prepared by mechanical milling of elemental Fe, Ni, Co, Cr, and Cu powders in an equiatomic ratio for 60 h. XRD analyses revealed that HEA contains predominant FCC phase along with BCC minor phase. In order to evaluate the effectiveness of FeNiCoCrCu HEA as a binder of WHA, in this study, W and HEA were mixed in the ratio of 9:1, pressed and sintered at temperatures of 1470 and 1500 °C for dwell time of 1 h 30 min under hydrogen atmosphere. These sintered samples are mentioned as WHEAs (W-High Entropy Alloys). The evolution of phases, microstructures, and mechanical properties was investigated as a function of sintering temperature vis-á-vis those prepared by mixing of W and Fe, Ni, Co, Cr, Cu in the same proportion as in HEA (W-EleMental: WEM). The effect of hydrogen treatment (HyT) prior to the sintering of WHEAs on above mentioned characteristics was studied. Structural investigation of WEMs and WHEAs showed high intense W-peaks. Micrographs of these sintered samples showed typical liquid phase sintered microstructures having three distinct phases: bright W-phase, gray matrix phase, and black Cr-oxide phase. With the increase of sintering temperature and introduction of HyT step, the volume fraction of solid W-grain has been increased and W-content in the matrix of WHEAs is reduced. Upon sintering, WHEAs yield better densification, higher compressive strength, and higher bulk hardness. This increase of strength from WEMs to WHEAs was attributed to better densification of WHEAs compared to the former. The maximum values of compressive strength (1912 ± 14 MPa) and bulk hardness (479 ± 16 VHN) were achieved in the case of hydrogen treated W-HEA powder sintered at 1500 °C.

Sintering behavior and ionic conductivity of Li1.5Al0.5Ti1.5(PO4)3 synthesized with different precursors

Abstract Li1.5Al0.5Ti1.5(PO4)3 (LATP) powders were prepared from different NO x -free precursors using an aqueous-based solution-assisted solid-state reaction (SA-SSR). The sintering behavior, phase formation, microstructure and ionic conductivity of the powders were explored as a function of sintering temperature. The powders showed a relatively narrow temperature windows in which shrinkage occurred. Relative densities of 95% were reached upon heating between 900 and 960 °C. Depending on the morphological features of the primary particles, either homogeneous and intact microstructures with fine grains of about <2 µm in size or a broad grain size distribution, micro-cracks and grain cleavages were obtained, indicating the instability of the microstructure. Consequently, the ceramics with a homogeneous microstructure possessed a maximum total ionic conductivity of 0.67 mS cm−1, whereas other ceramics reached only 0.58 mS cm−1 and 0.21 mS cm−1.

The influence of processing methods on the dielectric properties of BaTi1-xGdxO3-x/2 - Based materials

In this study, the intermediate rare-earth oxide Gd2O3 (Gd) was substituted in different amounts (x = 0.2–2 mol%) for the formulation of BaTi1-xGdxO3-x/2 (BTGx) dielectric materials. The effect of B-site substitution was confirmed by the additional Raman active A1g octahedral peak at ~835cm-1 strengthened at x ≥ 0.4 mol%. Additionally, properties of 0.9BTG0.007-0.1BA dielectric ceramics were analysed based on the influence of various processing methods as a function of sintering temperature. The focal samples were labelled Method-A (direct-mix) and Method-B (indirect-mix). As the sintering temperature (1075–1200 °C) increased, the 1 kHz response of the ε–T curves of Method-A samples transformed from a single peak to broad-narrow double peaks of high dielectric loss tangent (tan δ). Nonetheless, samples of Method-B possessed a clearly defined transmission electron microscopy (TEM) core-shell structure, flattened double-peak ε-T curves, optimised dielectric properties (ε = ~1563–1851 and tan δ < 1.5% at room temperature), and a wide-ranging temperature behaviour that meets the X8R dielectric standards (ΔC/C25°C < ±15%). The maximum dielectric breakdown strength of Method-B samples reached ~131 kVcm, while the energy storage density was ~0.726 J/cm3 at a maximum efficiency of ~80% at 1100 °C. Thus, exhibiting good potentials for balancing temperature stability with energy storage applications.

Temperature-stable and ultralow-loss (1 − x)CaSmAlO4–xSr2TiO4 microwave dielectric solid-solution ceramics

The (1 − x)CaSmAlO4–xSr2TiO4 (0.01 ≤ x ≤ 0.06) microwave dielectric ceramics were for the first time prepared by a conventional solid-state method. The phase composition, sintering behavior, microstructure and microwave dielectric properties were investigated as function of sintering temperature and composition. A single-phase solid solution with K2NiF4-type tetragonal structure was formed in the range of 0.02 ≤ x ≤ 0.06. All samples are well densified with very little pores. The addition Sr2TiO4 greatly improves dielectric properties originally by restraining the secondary phase and then deteriorates Q × f value because of decreasing tolerance factor. Moreover, the τf value dominated by the thermal expansion coefficient increases lineally as x rises. Finally, excellent microwave dielectric properties of er ~ 18.1, Q × f ~ 140,433 GHz (8.5 GHz), and a near-zero τf ~ + 0.05 ppm/°C can be obtained in the x = 0.05 ceramic sintered at 1425 °C.

Enhanced mechanical and biological performances of CaO-MgO-SiO2 glass-ceramics via the modulation of glass and ceramic phases

This work reports a new CaO-MgO-SiO2 (CMS) bioactive glass-ceramic, using ZrO2 as a nucleus to modulate the ratios of glass and ceramic phases as a function of sintering temperature. Mg-rich bioactive CMS glass-ceramics exhibit advantages regarding mechanical strength (flexural strength ~190 MPa and compressive strength ~555 MPa), in-vitro and in-vivo biocompatibilities, and bone ingrowth. The high mechanical strengths could be attributed to the CaMgSi2O6 glass-ceramic and lower porosity. X-ray absorption spectra indicate an increased SiO covalent bond via the development of CaMgSi2O6 glass-ceramics. From the in-vitro cytotoxicity and BMSC differentiation assays, the CMS samples sintered above 800 °C exhibited better cell attachment and differentiation, possibly due to structural stability, appropriate pore, and ion release to boost osteogenesis. Compared to hydroxyapatite (HA) ceramics, the CMS glass-ceramics display higher mechanical strengths, biocompatibility, and osteoconductivity. An in-vivo experiment demonstrated a fine bone-ingrowth profile around the CMS implant. This study may further the application of CMS glass-ceramics in bone implants.