Varying Sintering Temperature Research Articles

Effect of MnO2 doping and temperature treatment on optical energy band gap properties in Zn-Bi-Ti-O varistor ceramics

In this study, the optical band-gap energy (Eg) was investigated with respect to MnO2 and sintering temperatures on ZnO based varistor ceramics. Eg of the ceramic (99-x) mol% ZnO + 0.5 mol% Bi2O3 + 0.5 mol% TiO2 + × MnO2 where × = 0, 0.2, 0.4, 0.6 and 0.8 mol%, were determined using UV-Vis spectrophotometer. The samples was prepared through solid-state route and sintered at the sintering temperature from 1110, 1140 and 1170 °C for 45 and 90 min in open air. At no doping of MnO2, the values of Eg are 2.991 ± 0.001, 2.989 ± 0.001 eV for 45 and 90 min sintering time; respectively. Eg was decreased to 2.192 ± 0.001 eV at 1140 °C at 45 min sintering time. Similar result of Eg was observed at longer heat treatment. Further addition of dopant causing the Eg decreases rapidly to 2.099 and 2.106 ± 0.001 eV at 45 and 90 min sintering time; respectively. XRD analysis indicates that there is hexagonal ZnO and secondary phases, Zn2MnO4, Bi4Ti3O12 and Zn2Ti3O8. The relative density of the sintered ceramics decreased or remain constant with the increase of MnO2 concentration for 45 min sintering time, however, further prolong sintering time; the relative density decreases form 90.25 to 88.35%. This indicates the pores are increasing with the increase of heat treatment. The variation of sintering temperatures to the optical band gap energy of based ZnO varistor doped with MnO2 due to the formation of interface states.

Influence of sintering temperature on structural, morphological and magnetic properties of barium hexaferrite nanoparticles

Barium hexaferrite nanoparticles are attractive for modern data storage and microwave devices due to their unique properties. Single phase synthesis of barium hexaferrite using sol–gel auto-combustion route was optimized by varying sintering temperature and time. X-ray diffraction confirmed single phase hexagonal crystal structure of the sample sintered at 1100[Formula: see text]C for 2 h. Crystallite size, as determined using Scherrer’s formula, was increased with the increase in sintering temperature while the porosity remained nearly unchanged. Field emission scanning electron microscope (FE-SEM) revealed that grain size was increased from nanometers to micrometers by rising the sintering temperature and the shape of particles was platelet-like hexagonal at 900[Formula: see text]C. Vibrating sample magnetometer (VSM) exhibited that saturation magnetization and coercivity increased with the increase of sintering temperature. Maximum saturation magnetization and coercivity values were 36.80 emu/g and 5365 Oe, respectively, for the sample sintered at 1100[Formula: see text]C for 2 h.

Grain size disposed structural, optical and polarization tuning in ZnO

Structural, optical and polarization properties were investigated in different batches of ZnO synthesized by sol–gel method at varying sintering temperature. The structural visualization and charge scattering density analysis on the basis of X-ray diffraction data indicate polarized nature of sample. The structure- and polarization-related parameters were determined from Raman and Fourier transformed infrared spectroscopy data. Urbach energies and band gap were calculated using UV–visible spectroscopy. We observed increase in polarization, decrease in optical activity and band gap with increasing grain size without any increase in defects. Distortion in ZnO tetrahedra resulted in nonlinear optical behaviour above band edges. The results show direct correlation between grain size, band gap, optical behaviour and polarization. Low band gap and high polarization in ZnO can be employed for the production of opto-electronic devices.

Grain size-dependent dielectric, piezoelectric and ferroelectric properties of Sr2Bi4Ti5O18 ceramics

Fine powders comprising nano-crystallites of Sr2Bi4Ti5O18 (SBT) were synthesized via citrate-assisted sol–gel route. Different ceramics of SBT with different grain sizes (93 nm–1.42 μm) were fabricated by varying sintering temperatures and durations. The usage of nano-crystalline powders for fabricating ceramics facilitated lower sintering temperatures. The grain growth in these powder compacts was found to be controlled by the grain boundary curvature mechanism, associated with the activation energy of 181.9 kJ/mol. Interestingly, with a decrease in grain size there was an increase in structural distortion which resulted in a shift of Curie temperature (phase transition) toward higher temperatures than that of conventional bulk ceramics. Extended Landau phenomenological theory for the spherical ferroelectric particles was invoked to explain experimentally observed size-dependent phase transition temperature, and the critical size for SBT is predicted to be 11.3 nm. Grain size-dependent dielectric, ferroelectric and piezoelectric properties of the SBT ceramics were studied and the samples comprising average grain size of 645 nm exhibited superior physical properties that include remnant polarization (2Pr) = 16.4 μC cm−2, coercive field (Ec) = 38 kV cm−1, piezoelectric coefficient (d33) = 22 pC N−1 and planar electromechanical coupling coefficient (kp) = 14.8 %.

Microstructure and mechanical properties and of pulse plasma compacted WC - Co

Tungsten carbides-based inserts have been considered as one of the dominant hard materials in the cutting industry, receiving great interest for their excellent combination of mechanical properties. Pulse plasma compaction (PPC) process has been applied to a series of WC-Co samples with varying sintering temperature, initial particle size and sintering pressure in order to study the mechanical and microstructural behaviour. The quality of the products, as well as the mechanical properties and microstructural features this process yields, are commendable and worth looking into. A high hardness of more than 2000HV has been achieved while a maximum fracture toughness of 15.3MPa√m was recorded in samples that were sintered at 1100°C and 100MPa. Microstructural features like grain growth and other properties are discussed with respect to the varying parameters. While grain size shows an incremental pattern with increasing temperature, it was still possible to limit them to a great extent ensuring high mechanical properties. The effect of sintering pressure in the range of 60–100MPa, while keeping sintering temperature constant, was found to be almost negligible.

Study synthesis of (Lai1-xGdx)Ba2Cu3O7-δ superconductors at low temperature

This study has been conducted on synthesis of (La1-xGdx)Ba2Cu3O7-δ superconductors with the substitution of Gadolinium (Gd) (x = 0.25, 0.5, 0.75, 1) and sintering temperature (700-960oC) variation using a wet-mixing method. Characterization is done by XRD, RAMAN and SEM. XRD characterization results of all samples have shown sharp peaks which indicate that the sample had crystallized well. Search match results showed an impurity phase such as BaCO3, CuO and BaCuO2. Rietveld analyses for all samples gave decreasing lattice parameters (a-axis from 3.9069 to 3.8936 Å, b-axis from 3.9231 to 3.9055 Å and c-axis from 11.8489 to 11.6597 Å) with the addition of Gd contents (from 0.25 to 1.00). Such addition also caused a decrease of lattice parameters (a-axis from 4,901 to 3.8975 Å, b-axis from 3.9658 to 3.8986 Å and c-axis from 11.7254 to 11.6758 Å) with the addition of sintering temperature (from 700 to 960oC). Characterization of FTIR seen the bending vibration absorption by CO32-, absorbs mode apical oxygen of La (Gd) -O-Cu(2) and Cu(1)-O(1)-Cu(2). The addition of sintering temperatures also increases the intensity of the superconducting phase, reduce the intensity of an impurity phase (based on search results match) and increase the particle size (based on SEM characterization and Scherrer calculation).

Transparent single crystalline ZrO2-SiO2 glass nanoceramic sintered by SPS

Transparent ZrO2-SiO2 glass ceramics show potential for application in the dental industry. The application of this material prepared by a sol-gel method was hindered by the difficulties in obtaining large dimension samples. Spark plasma sintering (SPS) offers the possibility of achieving transparent ZrO2-SiO2 glass ceramics. In this study, a ZrO2-SiO2 powder was prepared by the sol-gel method and subsequently sintered by SPS. Varied sintering temperatures and pressures were explored to achieve better mechanical strength and transparency. TEM results showed single crystalline ZrO2 spherical nanocrystals (approximately 20nm) homogenously embedded in the SiO2 matrix. Tetragonal ZrO2 was the only crystalline phase in all specimens. With sintering conditions of 1200°C and 30MPa, a glass ceramic with fracture toughness of 4.13MPa m was obtained. This value is similar to the commercial dental glass ceramic of IPS e.max® Press. The studied transparent glass ceramic with high transparency and moderate mechanical strength shows promise for dental application.

Al stabilized Li7La3Zr2O12 solid electrolytes for all-solid state Li-ion batteries

All Solid State Lithium Ion Batteries (ASS-LIB) have been attracting great attention due to their high temperature stability, energy density and safety. Cubic Li7La3Zr2O12 (LLZO) ceramic electrolyte is one of the most studied solid electrolyte because of its exceptionally high chemical stability against Li metal, air and moisture, thermal stability and very competitive ionic conductivity. In order to stabilize cubic LLZO, relatively high temperatures are required. On the other hand, it's possible to decrease sintering temperature and time with a stabilizer addition. In this study, 20–30 mol % Al containing LLZO electrolytes were prepared by solid state reaction method at varying sintering temperatures (1100 °C and 1150 °C) for varying sintering times (12 h and 24 h) and the characterization of resultant materials were carried out. XRD results showed that, small amount of other compounds such as LaAlO3 were present in the sample produced at 1100 °C–12 h along with the main phase of cubic LLZO structure. According to SEM images, the sintering temperature was found to be more effective than sintering time on the densification behaviour. Existing porosities were reduced when both sintering temperature and time were increased. Different amount of Al addition did not have an effect on the densification behaviour. Both intergranular and transgranular types of fractures were observed by SEM. Finally it was found that 30 mol % Al containing samples sintered at 1150 °C for 12 h showed mixed conductor behaviour, whereas for 24 h and 36 h pellets showed ionic conductor behaviour.

Microstructural surface analysis of Ni/Cu front contact after peel force test to improve contact adhesion

ABSTRACTNi/Cu two-step plating has been applied to solar cells as a metallization technique since it has low contact resistance after nickel sintering process, and is suitable for fabricating narrow fingers. However, a reliable adhesion of the Ni/Cu contact is still one of the remaining challenges. In this experiment, a peel force test was used to investigate the dependence of varied sintering temperatures on the adhesion of the Ni/Cu front contact. The surface of the bus bars was observed by field emission scanning electron microscope (FE-SEM) to analyse the high and low adhesion regions. When the adhesion result was high, silicon chunks from the substrate were often observed on the nickel layer (ribbon side). Also, the influence of oxidation on the nickel surface during sintering was discussed with the oxygen atomic ratio, which was measured by energy dispersive spectroscopy (EDS). Decent adhesion values up to 1.16 N/mm average with 2.47 N/mm maximum have been achieved with good soldering process.

Novel blue-emitting phosphors - BaBeSiO_4:Eu^2+: luminescence properties and its application for UV-light emitting diodes

A new Eu2+-doped barium beryllium silicate, BaBeSiO4:xEu2+ (1% ≤ x ≤ 10%) phosphor was successfully synthesized by the high temperature solid-state reaction. The phosphor system was investigated as a novel candidate for phosphor-converted white light-emitting diode (LED) applications. The evolution of luminescence and structure of the phosphors induced by variation of sintering temperature are investigated using photoluminescence spectra and X-ray diffraction techniques. The concentration quenching and thermal quenching process of the phosphor were also investigated in detail. The BaBeSiO4:Eu2+ phosphor exhibits broad excitation spectra ranging from 250 to 400 nm, and a blue emission band centered at 460 nm under λex = 337 nm. The main parameters of the electron-vibrational interaction, such as Huang-Rhys factor, effective phonon energy, and zero-phonon line position, were all estimated. The optimal concentration of Eu2+ ions in BaBeSiO4 was determined to be 3 mol.%. The corresponding concentration quenching mechanism was verified to be the electric dipole−dipole interaction. The activation energy of BaBeSiO4:Eu2+ for thermal quenching was calculated to be 0.19 eV with the Arrhenius equation. The LED device exhibited an excellent color-rendering index Ra of 90.13 at a correlated color temperature of 4077 K with CIE color coordinates of (0.38, 0.39) under a 350 mA forward-bias current. Based on these results, we are currently evaluating the potential application of BaBeSiO4:Eu2+ as a white-emitting UV-convertible phosphor for high power LED applications.

Effect of sintering temperature variations on fabrication of 45S5 bioactive glass-ceramics using rice husk as a source for silica

45S5 bioactive glass is a highly bioactive substance that has the ability to promote stem cell differentiation into osteoblasts — the cells that create bone matrix. The aim of this work is to analyze physical and mechanical properties of 45S5 bioactive glass fabricated by using rice husk ash as its silica source. The 45S5 bioactive glass was prepared by melting the batch at 1300°C for 3h. The samples were sintered at different temperatures ranging from 900 to 1050°C with a fixed dwell-time of 2h. The phase transitions, density, porosity and microhardness values were investigated and reported. DTA analysis was used to examine the crystallization temperatures of the glasses prepared. We found that the sintering temperature had a significant effect on the mechanical and physical properties of the bioactive glass. The XRD showed that when the sintering temperature was above 650°C, crystallization occurred and bioactive glass-ceramics with Na2Ca2Si3O9, Na2Ca4(PO4)2SiO4 and Ca3Si2O7 were formed. The optimum sintering temperature resulting in maximum mechanical values was around 1050°C, with a high density of 2.27g/cm3, 16.96% porosity and the vicker microhardness value of 364HV. Additionally, in vitro assay was used to examine biological activities in stimulated body fluid (SBF). After incubation in SBF for 7days, all of the samples showed formations of apatite layers indicating that the 45S5 bioactive glasses using rice husk as a raw material were also bioactive.

Microwave dielectric properties of 0.93Mg0.95Zn0.05TiO3–0.07(Ca0.8Na0.1La0.1)TiO3 ceramic system

The phase formation, microstructures and microwave dielectric properties of 0.93Mg0.95Zn0.05TiO3–0.07(Ca0.8Na0.1La0.1)TiO3 ceramic system prepared by the conventional solid-state reaction route were investigated with the variation of sintering temperature, aiming to achieve a material with a high quality factor and nearly zero temperature coefficient of resonant frequency. The microwave dielectric properties of the ceramic system were found strongly related to the density, sintering temperature, second phase as well as the microstructure of the samples. The 0.93Mg0.95Zn0.05TiO3–0.07(Ca0.8Na0.1La0.1)TiO3 ceramic sintered at 1225°C showed excellent microwave dielectric properties with εr~22.5, Q×f~79300GHz (at 8GHz) and τf~−0.14×10−6/°C. This finding could be a new candidate material utilized for microwave applications with low loss and temperature-stable characterizations.

저온소결 8/65/35 PLZT 세라믹의 전기열량 효과

In this study, in order to develop the composition ceramics with the excellent electrocaloric properties, 8/65/35 PLZT ceramics were fabricated by the conventional solid-state method with the addition of , CuO, and the variation of sintering temperature from to . The XRD pattern of all specimens indicated general perovskite structure and the rhombohedral phase were observed. Curie temperature () of all specimens was observed in the vicinity of about . Density, coercive field and remnant polarization of the specimen sintered at was , 8.895 kV/cm, , respectively. EC effect of PLZT ceramics was measured by indirect method and the temperature change due to the electrocaloric effect was calculated by Maxwell`s relations. of ceramic sintered at was under application of 40 kV/cm at .

Influence of sintering temperature on the structure and high-temperature discharge performance of LiNi1/3Mn1/3Co1/3O2 cathode materials

Layered cathode materials of high-temperature lithium batteries, LiNi1/3Mn1/3Co1/3O2 are synthesized by a sol-gel method with variation in final sintering temperature for borehole applications. The structure, morphology and high-temperature discharge performance of these resulting products are investigated by X-Ray Diffraction (XRD), scanning electron microscopy (SEM), laser particle size analysis, galvanostatic and pulse discharge. The results of structural analysis indicate that the sample sintered at 800 °C has the characteristics of good crystallinity, narrow size distribution and large specific surface area at the same time. The discharge experiments also indicate that this sample has the best electrochemical properties, with the maximum discharge capacities of 314.57 and 434.14 mAh·g-1 at 200 and 300 °C respectively and the minimum cell internal resistances at both temperatures.

Mechanical behaviors of porous Ti with high porosity and large pore size prepared by one-step spark plasma sintering technique

Porous Ti with 38–56% porosity and 50–500 μm pore size was prepared by one-step spark plasma sintering (SPS) method using modified mold combined with space holder (ammonium hydrogen carbonate, NH4HCO3) technique. Pore characteristics and mechanical behaviors of porous Ti were investigated by varying sintering temperatures (1000–1200 °C). Results showed that porous Ti prepared by SPS had large plasticity and the compressive cyclic stress-strain curves showed nonlinear recovery and hysteresis effect. With the sintering temperature increasing, smooth and dense pore walls, and relatively isotropic pore surface of porous Ti were obtained, the elastic modulus and compressive strength increased. The recoverable strain ratio of porous Ti after five cycles could reach more than 70% at the pre-strain of 2%. When temperature was 1200 °C, the good combination of interconnected pore characteristics, proper elastic modules (11.2 GPa, close to that of human bones), higher compressive strength (287 MPa) and stable recoverable behaviors of porous Ti, made this material possible to be used for load-bearing hard tissue implants.

The Effect of Milling Time and Sintering Temperature on Synthesis of PbTiO<sub>3</sub> by Mechanical Alloying

PbTiO3 is one of electroceramic materials which can be applied for electronics and microelectronics due to their dielectric, pyroelectric, and piezoelectric properties. The members of PbTiO3-based ferroelectrics are widely used in multilayer, actuator and sensor capacitor. At room temperature, PbTiO3 has a tetragonal perovskite structure. In this research, PbTiO3 particles are synthesized by mechanical alloying method with variation of milling time and sintering temperature. The milling time variation is taken for 10, 20 and 30 hours. Sintering temperature variation is performed at 850, 900 and 1000°C. The powders used in the milling process are PbO and TiO2 powders. X-Ray Diffraction (XRD) and Scanning Electron Microscopy–Electron Difraction X-ray (SEM-EDX) are performed to analyze the formation of PbTiO3 phase. It is found that the synthesized powders contain 100% PbTiO3 phase for all sintering temperatures. The PbTiO3 particles have agglomeration shape with a broad particle size. The electrical properties of PbTiO3 are measured using electrical test device. Electricity test analysis shows that the synthesized PbTiO3 behaves as semiconductor-like.

Effects of binder system and processing parameters on formability of porous Ti/HA composite through powder injection molding

Abstract Porous titanium-hydroxyapatite (Ti/HA) composite is a developed composite material suitable for bio-medical applications. Powder injection molding (PIM) with space holder method is used to produce porous Ti/HA with mechanical properties, similar to human bone, and pores helps to initiate tissue growth. However, the differences in physical and mechanical properties of these composites are the main challenges during debinding and sintering. Therefore, the main objective is to determine effects of binder systems and processing parameters on formability of Ti/HA composite. In PIM, a binder system is necessary to produce green and ultimately sintered part. There are two binder systems and variation of sintering temperature has been used. Results revealed that Polyethylene glycol (PEG)-based binder system is applicable with NaCl space holder and optimum sintering parameters, including temperature, heating rate, and holding time of 1300 °C, 10 °C/min, and 5 h, respectively. The fabricated porous Ti/HA exhibits average porosity, pore size distribution, compressive strength, and roughness values of 55%, 60 μm to 170 μm, 370 MPa, and 0.323 μm, respectively. FESEM results showed that the pores are interconnected. It may be an appropriate material for future bio-medical applications.

Effects of Sintering Temperature and Porogen Addition on Properties of Low Cost Porous Mullite Ceramics

In the present paper, low cost porous mullite ceramics with high porosity, high strength and low thermal conductivity were fabricated using ceramic waste powder and clay as raw materials, and sawdust as porogen. The correlation of phase composition and physicochemical properties of such porous mullite ceramics were researched by varying sintering temperature and the extra addition of sawdust. The results show that: The ceramics show the best comprehensive properties when the sintering temperature is 1400 oC and the addition of sawdust is 30wt%. The results of SEM and EDS analysis confirm that new mullite phase is generated in the ceramics, which can strengthen the ceramics. And the best value of the bulk density, apparent porosity, cold crushing strength and the thermal conductivity of the prepared ceramics is 0.96g.cm-3,60.7%,5.3MPa and 0.212W·m-1·K-1, respectively.

Role of hybrid reinforcement on microstructural observation, characterization and consolidation behavior of AA 6061 nanocomposite

The present investigation had dealt with the synthesis, characterization and consolidation behavior of AA 6061 nanocomposites reinforced with hybrid (TiC+Al2O3) nanoparticles with varying weight percentages (0.0, 0.5, 1.0, 1.5 and 2.0wt.%) prepared by 30h of mechanical alloying (MA) and compared with 2wt.% of various reinforcements such as titanium carbide (TiC), multi-walled carbon nanotubes (MWCNTs), gamma phase alumina (γ-Al2O3) nanoparticles. The microstructure, grain size, lattice strain and lattice parameter of the above powders were examined using different analysis techniques including X-ray diffraction (XRD) analysis, scanning electron microscope (SEM), transmission electron microscope (TEM) and energy dispersive spectrometry (EDS). The compressibility and sinterability of the prepared nanocomposites at varying sintering temperatures and varying compaction pressures were also studied. Consolidation behavior in terms of particle rearrangement and plastic deformation mechanisms were evaluated by Balshin, Heckel, Panelli and Ambrosio Filho and Ge linear compaction equations. The effect of hybrid and nanolevel reinforcements on mechanical properties such as green compression strength, Vickers hardness and density of nanocomposites were evaluated. Among the above nanolevel reinforcements, hybrid (TiC+Al2O3) and TiC nanoparticles gave maximum green compression strength (211 and 233MPa) and maximum hardness (985 and 1186MPa) for 2wt.% addition to AA 6061 matrix after 30h of MA.

Superelastic behaviors of biomedical porous NiTi alloy with high porosity and large pore size prepared by spark plasma sintering

A process of combing use of one-step spark plasma sintering (SPS) method and space holder technique was developed to have successfully fabricated the porous NiTi alloy. To optimize porous NiTi for bone implant applications, the effects of pore characteristics and microstructures on mechanical properties and superelastic behaviors of the porous NiTi alloys were investigated by varying sintering temperatures (800–1050°C) and ammonium hydrogen carbonate (NH4HCO3) contents (0–20wt.%). The results showed that porous NiTi alloys with 18–61% porosity and 21–415μm average pore size all consisted of nearly single NiTi phase with few undesired phases Ti2Ni and Ni3Ti. The superelastic recovery strain ratio of the porous NiTi alloy could be improved up to 90% through training, but with further increasing of training cycles, the curves showed an obvious ladder shaped stress plateau, which indicated the collapse of the pores. This enhanced superelasticity will greatly degrade the mechanical mismatch between bones and porous NiTi. Furthermore, with increasing the porosity and pore size, elastic modulus and compressive strength of the porous NiTi alloys decreased. However, the compressive strength was higher or close to those of human bone and the elastic modulus was close to those of human bone. The unique combination of inter-connected pore characteristics, pure phase composition, low elastic modulus, high strength and large superelastic recovery strain made this material a good candidate for ideal long-term load-bearing hard tissue implants.