Effect Of Firing Conditions Research Articles

The effect of firing conditions on the characteris-tics of thick-film resistors for temperature sensors

The effect of firing conditions on the characteris-tics of thick-film resistors for temperature sensors

Effect of Firing Conditions on Phase Formation, Microstructure, and Electrical Properties of (K0.5Na0.5)(Nb0.7Ta0.3)O3 Ceramics Synthesized by Solid-State Combustion Method

The effect of the firing conditions on the phase formation, microstructure, and electrical properties of (K0.5Na0.5)(Nb0.7Ta0.3)O3 (KNNT) ceramics synthesized by the solid-state combustion technique using glycine as fuel has been investigated. All samples were calcined at 600°C to 800°C for 2 h and sintered at 1150°C to 1190°C for 2 h to 5 h. Pure KNNT powders were produced after calcination at 600°C for 2 h. The average particle size increased when the calcination temperature was increased. The KNNT powder calcined at 600°C for 2 h showed rather square morphology with average particle size of ∼ 160 nm. The x-ray diffraction (XRD) analysis results for the ceramics revealed the presence of orthorhombic (O) and tetragonal (T) phases in all samples. When sintering at 1150°C for 4 h, the O:T ratio was 50:50, as verified by the Rietveld refinement technique. The average grain size, density values, and dielectric properties tended to increase when the dwell time was increased from 2 h to 4 h, but then degraded. The KNNT ceramic produced at the optimum firing condition (1150°C for 4 h) showed good crystalline morphology, the highest density (ρ = 5.28 g/cm3), the highest dielectric constant (eC = 5002), and good ferroelectric behavior (Pr = 18.50 μC/cm2 and Ec = 9.04 kV/cm).

Effect of firing conditions & release height on terminal performance of submunitions and conditions for optimum height of release

Abstract Submunitions should exhibit optimum terminal performance at target end when released from certain pre-determined height. Selection of an optimum height of release of the submunitions depends on the terminal parameters like forward throw, remaining velocity, impact angle and flight time. In this paper, the effects of initial firing conditions and height of release on terminal performance of submunitions discussed in detail. For different height of release, the relation between range and forward throw is also established & validated for a number of firing altitude and rocket configurations.

Low Firing Temperatures and High Ferroelectric Properties of (Ba0.85Ca0.15)(Ti0.90Zr0.10)O3 Lead-Free Ceramics Synthesized by the Combustion Technique

This work studied the effect of firing conditions on phase formation, microstructure and electrical properties of (Ba0.85Ca0.15)(Ti0.90Zr0.10)O3;(abbreviated as BCTZ) ceramics, which were synthesized through the combustion technique. To reduce the reaction temperature, glycine was used as fuel with a ratio of raw material: glycine (1:1.11). BCTZ samples were calcined at 900–1200°C for 2 h and sintered at 1350 –1550°C for 2 h. Ultrafine BCTZ powder and single peroveskite phase were achieved from the sample calcined at 1050°C for 2 h.These results were obtained at a lower temperature and with shorter dwell time than those obtained using the solid state reaction method by ∼150°C and 1 h, respectively. The BCTZ ceramics exhibited a coexistence of rhombohedral and orthorhombic phase in all samples. The average particle size and the average grain size increased from 172 to 295 nm and 0.82 to 2.57 µm, respectively, when firing temperatures increased. The highest density (5.76 g/cm3), highest dielectric constant (ϵr ≅ 4485 and ϵmax ≅ 14897) and best ferroelectric properties (Pr ≅ 18.47 μC/cm2 and EC ≅ 4.52 kV/cm) were obtained from the sample sintered at 1450°C for 2 h.

The effect of firing conditions on electrical conductivity and electrochemical properties of Sr0.8La0.2TiO3–Ce0.9Gd0.1O1.95 composite anodes for solid oxide fuel cells

The electrical conductivity of Sr0.8La0.2TiO3 (SLT) increased significantly through reducing calcination and sintering processes. The electrical conductivity of SLT sintered three times under a reducing atmosphere was 249Scm−1 at 800°C in a H2 atmosphere, which is 40 times higher than that of SLT sintered in air. The enhanced electrical conduction might be caused by the variation in valence state from Ti4+ to Ti3+. The single-cell performance of the Sr0.8La0.2TiO3–Ce0.9Gd0.1O1.95 (SLT–GDC) composite anode improved with increasing amount of GDC. The SG (HHH)15 anode exhibited the highest maximum power density of 25mWcm−2 at 800°C for CH4 fuel.

The effect of firing conditions on phase formation, microstructure and dielectric properties of BNKTNb-LSb ceramics prepared via the combustion technique

The fabrication of 0.99[Bi0.5(Na0.82K0.18)0.5Ti0.995Nb0.005O3]-0.01LiSbO3 ceramics (BNKTNb-LSb) prepared by the combustion technique was studied. A single perovskite phase of BNKTNb-LSb powder was observed by the powders calcined at 700 °C for 2 h, which was lower than the solid-state reaction technique ∼150 °C. The BNKTNb-LSb ceramics showed the coexistence of a rhombohedral and tetragonal phase at a low sintering temperature. Then, the phase formation changed from a tetragonal to a pseudocubic phase when sintered at higher temperatures. The grain morphology of the BNKTNb-LSb ceramics exhibited a rather square shape and the average grain size of the ceramics was increased with increased sintering temperatures. The density, linear shrinkage, ϵr and ϵmax of the BNKTNb-LSb ceramics tended to increase with increasing sintering temperatures up to 1125 °C and then decreased. At 1125 °C, the highest density, shrinkage, ϵr and ϵmax were about 5.82 g/cm3, 18.7%, 1625 and 4465, respectively. The dielectric behavior corresponded with the XRD, density and the microstructure results.

Dielectric and ferroelectric properties of PMN–PT–PZ ceramics prepared via combustion technique

The fabrication of 0·53Pb (Mg1/3Nb2/3)O3–0·37PbTiO3–0·10PbZrO3 (PMN–PT–PZ) ferroelectric ceramics using the combustion technique and the effects of firing conditions on the phase structure, microstructure and electrical properties of the powders and ceramics were studied. Glycine was used as a fuel to reduce the reaction temperature. It was found that a single perovskite phase of PMN–PT–PZ powders was obtained from the sample calcined at 900°C for 2 h. The conventional technique uses two steps in the calcination process. The use of glycine in the combustion technique reduced the process to one step. The morphology of the PMN–PT–PZ powders showed an almost spherical shape and the average particle size increased from 0·12 to 2·51 μm when the calcination temperature was increased from 700 to 1000°C. The pure PMN–PT–PZ ceramics exhibited coexistant phases of the rhombohedral and the tetragonal perovskite phase in the samples sintered at a temperature lower than 1100°C. A second phase of pyrochlore was found in the samples sintered at temperatures higher than 1150°C. The PMN-PT-PZ ceramics sintered at 1100°C for 2 h exhibited the highest density, highest linear shrinkage and highest dielectric constant at Tc of 7·72 g cm−3, 16·13% and 18337 respectively. The densest PMN-PT-PZ ceramic exhibited good ferroelectric properties of (using an electric field at 30 kV cm−1) Pr = 26·9 μC cm−2 and Ec = 4·5 kV cm−1.

On the Conduction Mechanism of Silicate Glass Doped by Oxide Compounds of Ruthenium (Thick Film Resistors). 3. The Minimum of Temperature Dependence of Resistivity

This article is the final part of the investigation of conduction mechanism of silicate glass doped by oxide compounds of ruthenium (thick film resistors). In the first part [1], the formation of percolation levels due to diffusion of dopant atoms into the glass has been considered. The diffusion mechanism allowed us to explain shifting of the percolation threshold towards to lower value and the effect of firing conditions as well as the components composition on the electrical conduction of the doped glass. The coexistence of thermal activation and localization of free charge carriers as the result of nanocrystalline structure of the glass was the subject of the second part [2]. Because of it, the resistivity of the doped silicate glass is proportional to exp (–aT–ζ) at low temperatures (T 50 K), 0.4 ζ T > 800 K) and the conductivity of the doped silicate glass decreases sharply. We consider the origin of the minimum in the temperature dependence of resistivity of the doped silicate glass here. It is shown that the minimum arises from merge of impurity band into the valence band of glass at temperature high enough, so thermal activation of charge carriers as well as its hopping are failed, and scattering of free charge carriers become predominant factor in the temperature dependence of the resistivity.

Effects of Firing Conditions on the Properties of Calcareous Clay Roofing Tiles

AbstractThe effects of firing conditions on the microstructure and physical properties of clay roofing tiles are studied. This research presents the effects of oxidizing and reducing atmosphere on Kanjiža clay material with carbonate content up to 22% by weight and the characterization of the final products. The firing was done both in the laboratory and under industrial conditions. The Fe2+/Fetotal ratio played a decisive role in the sintering process under a reducing atmosphere. The formed glassy phase, with the presence of Fe2+, attacked the earth-alkali oxides after the carbonate decomposition and more effectively filled smaller pores. The obtained results justified the benefits of the reducing firing atmosphere with 5% CO, lower porosity, higher frost resistance values, and changed microstructural characteristics

Effect of Firing Conditions on Phase Formation, Microstructure and Dielectric Properties of KNN-LS-BN Ceramics Fabricated by Combustion Technique

The 0.998[0.95(K0.5Na0.5NbO3–0.05LiSbO3)]-0.002BiNiO3; KNN-LS-BN ceramics has been prepared by the combustion technique using glycine as a fuel. A pure orthorhombic phase was obtained in the powder calcined at 750°C for 0.5 h. For the sintered pellets, a pure tetragonal structure was found in the ceramic sintered at 1100°C for 1–3 h using heating and cooling rate of 15°C/min. The average grain size and linear shrinkage were increased with the increasing of dwell time. The highest density, maximum dielectric constant and lowest dielectric loss at Tc with a value of 98.4%, 4872 and 0.1 were found in the sample sintered at 1100°C for 2 h using heating and cooling rate of 15°C/min.

Luminescent properties of CaAl4O7 powders doped with Mn4+ ions

Abstract In this work, the effects of firing conditions, the Mn concentration, and a flux on the structural and luminescent properties of Mn 4+ ion doped CaAl 4 O 7 (CA 2 ) powders were investigated. The photoluminescence excitation spectra of CA 2 :Mn 4+ powders exhibited a broad band, covering from around 320 to 400 nm. Four red emission bands were observed at around 644, 656, 666, and 671 nm, while the 656 nm emission was observed as the strongest one. CA 2 :Mn 4+ was believed to be a good candidate as a red phosphor for white light emitting diodes (LEDs) using near ultraviolet chips.

The effects of firing conditions on the properties of electrophoretically deposited titanium dioxide films on graphite substrates

Thick anatase films were fabricated on graphite substrates using a method of anodic aqueous electrophoretic-deposition using oxalic acid as a dispersant. Thick films were subsequently fired in air and in nitrogen at a range of temperatures. The morphology and phase composition were assessed and the photocatalytic performance was examined by the inactivation of Escherichia coli in water. It was found that the transformation of anatase to rutile is enhanced by the presence of a graphite substrate through reduction effects. The use of a nitrogen atmosphere allows higher firing temperatures, results in less cracking of the films and yields superior bactericidal performance in comparison with firing in air. The beneficial effects of a nitrogen firing atmosphere on the photocatalytic performance of the material are likely to be a result of the diffusion of nitrogen and carbon into the TiO 2 lattice and the consequent creation of new valence band states.

Effects of firing conditions and addition of Co on bulk and grain boundary properties of CGO

Commercial ceria–gadolinia powders were used to obtain bulk CGO samples, by sintering at 900 to 1500 °C with Co nitrate additions, or at temperatures in the range 1500–1600 °C, without Co. These samples were characterized by impedance spectroscopy in air, at temperatures in the range 150–600 °C, to distinguish the bulk and grain boundary behaviour. Addition of Co nitrate allows densification at lower temperatures and plays significant effects on both microstructural contributions of impedance spectra, enhancing the bulk and grain boundary conductivities and lowering their activation energy. Typical values of activation energy of bulk conductivity vary from 0.77 to 0.94 eV, and the activation energy of grain boundary conductivity were in the range 0.96–1.05 eV. The effects of sintering additive are spoilt on raising the sintering temperature, due to depletion of Co content in grain boundaries of samples fired at high temperatures. These observations indicate that grain boundary behaviour may be determined by segregation of Co and/or Gd and the corresponding space charge layers, at least for materials prepared from high purity precursor powders. The p-type electronic conductivity is also enhanced for samples fired at relatively low temperatures with addition of Co, thus indicating that significant changes in defect chemistry occur.

Effect of firing conditions, filler grain size and quartz content on bending strength and physical properties of sanitaryware porcelain

The effect of filler grain size, quartz content in the filler and firing conditions (sintering temperature, firing time) on the physical and mechanical properties of a sanitary-ware porcelain has been studied in the narrow range of values used by industrial practice. The investigation has been carried out using the Taguchi method for experimental design. Quartz grain size is the most important factor regarding the physical properties and dominates bending strength in two ways, directly by inducing compressive stresses to the vitreous phase and indirectly through the development of a favorable microstructure. The characteristics of the last are discussed in detail. The optimum grain size of quartz was found to be 5–20 μm. This results in 20–30% increase of bending strength compared to the reference porcelain. The results confirm the “Matrix Reinforcement” theory, however, the positive effect of mullite content on bending strength was not observed.

Effect of Firing Conditions on Three-dimensional Spectral Reflectance of Dental Porcelain for Metal-ceramics

Effect of Firing Conditions on Three-dimensional Spectral Reflectance of Dental Porcelain for Metal-ceramics

Photoluminescence of ZnGa 2O 4: Mn phosphor fired at vacuum atmosphere

The ZnGa 2O 4 phosphor doped with Mn 2+ was fired from the mixed of ZnO and Ga 2O 3, the effects of firing conditions and the emission characteristics were investigated. Zn 1− x Mn x Ga 2O 4 phosphors fired at air atmosphere, exhibits two emission bands with main peak at 506 nm (Mn 2+ emission center) and weak peak at 666 nm (Mn 4+ emission center). However, where as fired at vacuum atmosphere, the emission spectrum shown only 506 nm peak, and its intensity increase drastically. From its excitation spectrum, apart from 245 nm (the absorption peak of ZnGa 2O 4), there are two absorption peaks (304 and 626 nm) which derived from Mn 2+, these spectra fit the energy levels of 4T 1 (4P) and 4T 1 (4G) during Mn 2+ (3d 5) split. The green emission band of 506 nm can be excited by such a absorption peak, the highest intensity is provoked by 304 nm. The emission intensity of Zn 1− x Mn x Ga 2O 4 phosphors of 506 nm peak are strongest when firing in 10 −2 Torr vacuum atmosphere at 1300°C, 1.5 h and Mn 2+ concentration is x=0.006.

The effect of firing conditions on the properties of Bi2O3−TiO2−Fe2O3 films

It is shown that the firing conditions have a strong bearing on the microstructure and porosity of films and the diffusion processes that take place at the film—substrate (glass) interface. This makes a certain contribution to changes in the physical and physicochemical proeprties of sol-gel coatings.

Studies of the formation of α′ and α′-β′ sialon

Recently α′ and α′-β′ composite sialon ceramics have received much attention because of the hardness and the better thermal shock properties of α′-sialon materials. Phase relationships determined in the α′ plane show that α′-sialon expands from the pure nitride side towards the alumina side and there exists a fairly big region of α′-sialon in equilibrium with β′-sialon, thus providing the possibility to fabricate α′-β′ composite sialon ceramics. Because of the small difference in composition between α′ and β′ sialons, transformations between α′ and β′ occur very rapidly at firing temperatures in the presence of an appropriate grain-boundary liquid phase. Therefore, to control the transformation is of importance for fabricating both α′ and α′-β′ composite sialons and for this an understanding of reaction mechanisms is necessary. This paper describes the reaction sequences under different firing circumstances of α′ and α′-β′ sialon with Y as “modifying” cation, doped with or without La 2O 3 as densifying additive. The effect of firing conditions on transformation between α′ and β′ and the role of La 2O 3 on densification as well as the formation of α′-sialon are discussed.

Effect of firing conditions in the properties of porcelain

Effect of firing conditions in the properties of porcelain

Adherence-fracture energy of a glass-bonded thick-film conductor: effect of firing conditions

The effect of firing conditions on the adherence of a glass-bonded Pt-Au printed thick film conductor to a 96 wt % Al2O3 substrate was determined by a fracture mechanics measurement of the critical fracture energy for catastrophic thick film-substrate separation. The technique also demonstrated that separation by slow crack growth (delayed failure) occurred in this system. Analysis of the thick film microstructure and fracture surfaces showed that optimum adherence was primarily a result of a mechanically interlocked interface formed between the conductor metal and the glass bonding layer which, in turn, was strongly bonded to the alumina substrate. The two step decrease observed inγIC (from 3.7 to 0.2 J m−2) with firing temperatures over 860° C resulted from the removal of this interlocking metal-glass interface brought on by metal sintering and glass migration to the substrate. Thus, at 860° C firing temperatures, adherence is controlled by cohesive fracture in the glass bonding phase while above 1000° C it is controlled by adhesive failure of the weak chemical-physical bond at the metal-glass interface.