Effects of calcination temperature on phase and microstructure evolution of BaTi4O9 powders

Calcining of the mixture of BaCO₃ and TiO₂ with a ratio 1:4 at different temperatures was carried out to synthesize BaTi₄O₉ powders. Phase evolution of the samples was studied using the differential thermal analysis (DTA) and X-ray diffractometry (XRD). Both techniques confirmed that the formation of BaTi₄O₉ started around 1000 °C. The XRD peaks showed that BaTi₄O₉ was most pronounced at 1250 °C. X-ray line broadening methods were employed to study the variation of particle size and microstrain of the BaTi₄O₉ powders. The Voigt function in a single line and the pseudo-Voigt function in the variance methods were used in our case. We found that both functions resulted in the same trends, i.e., the particle size increased with the temperature with the biggest size of 180 and 160 nm, whilst the microstrain yielded the opposite trend with the lowest values of 6.2 × 10^–3 and 1.1 × 10^–3. The scanning electron microscopy (SEM) study revealed the size of the large particles formed, due to agglomeration, to be about 0.5–1.9 μm. Furthermore, it was shown that irregular shapes of BaTi₄O₉ powders necked to each other appeared at 1000 °C and grew into ellipse and rod shapes at 1250 °C. Electronic Publication     

Solution route synthesis of dendrite Cu6Sn5 powders, anode material for lithium-ion batteries

Intermetallic dendrite particles, such as Cu₆Sn₅ compound, possible anode materials for high power lithium-ion batteries, can be synthesized by using solution technique. Solution route method can induce the formation of the compound by performing a redox reaction between metal chloride salts and metallic reducing powder in a suitable solvent. The morphological features and single-phase formation corresponding to different processing conditions including solvent type, reducing agent particle size, and reaction temperature, were determined. The X-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM) results illustrate the dendritic morphology of Cu₆Sn₅ particles with small amount of impurities, which can be synthesized by using ethylene glycol as solvent and zinc powder as reducing agent. Reducing agent particle size and reaction temperature have a very small effect on the formation of the Cu₆Sn₅ dendrite powder.     

Analysis of X-Ray Diffraction Line Profiles of Lead Zirconate Titanate Using the Fourier Method

Lead zirconate titanate (PZT) powder was prepared by a solid state reaction. The X-ray line broadening produced in PZT powder was analyzed by the Fourier method to estimate particle size and microstrain. It was found that an increase of the annealing temperature caused the microstrain to decrease owing to an increase in particle size. The Scherrer formula used to calculate the particle size yielded considerably smaller values.     

Effect of Sintering Temperature on Phase Transition and Mechanical Properties of Lead Zirconate Ceramics

Phase transition and mechanical properties of PbZrO₃ (PZ) at different sintering temperatures were studied. The Curie temperature depends on the sintering temperature. Hardness and fracture toughness of the PZ were measured using Vickers and Knoop microhardness testers. The lower density at the higher sintering temperature resulting from the loss of lead oxide (PbO) causes the lower value of the Curie temperature, hardness and fracture toughness. The results were well corresponding to the microstructure of the PZ ceramics.     

Hybrid optical-electrochemical electronic nose system based on Zn-porphyrin and multi-walled carbon nanotube composite

In this work, we have enhanced the capability of an e-nose system based on combined optical and electrochemical transduction within a single gas sensor array. The optical part of this e-nose is based on detection of the absorption changes of light emitted from eight light emitting diodes (LEDs) as measured by a CMOS photo-detector. The electrochemical part works by measuring the change in electrical resistivity of the sensing materials upon contact with the sample vapor. Zinc-5,10,15,20-tetra-phenyl-21H,23H-porphyrin (ZnTPP) and multi-walled carbon nanotube (MWCNT) composite was used as the sensing materials based on its good optoelectronic properties. This sensing layer was characterized by UV-Vis spectroscopy and atomic force microscope and tested with various VOC vapors. Density functional theory (DFT) calculations were performed to investigate the electronic properties and interaction energies between ZnTPP and analyte molecules. It can be clearly seen that this hybrid optical-electrochemical electronic nose system can classify the vapor of different volatile organic compounds.     

Properties of hydroxyapatite/zirconium oxide nanocomposites

Effects of zirconium oxide (ZrO₂) nanoparticles additive on the microstructure and physical properties of hydroxyapatite (HA) were investigated. The HA powder was derived from natural bovine bone by a sequence of thermal processes. The composites containing nanoparticles of ZrO₂ (0.2–1.0 vol%) were fabricated by a solid-state reaction mixed oxide method. All samples showed traces of HA, beta-tricalcium phosphate (β-TCP) and alpha-tricalcium phosphate (α-TCP) phases while the x≥0.1 samples also showed ZrO₂ phase. Amount of β-TCP and α-TCP phases tend to decrease with ZrO₂. The additive inhibited grain growth as a result of a decrease in grain size. However, the x=0.2 sample exhibited higher hardness value which is consistent with the density data. In addition, bioactivity test suggested that the additive promoted an apatite forming with the values of Ca/P close to the value obtained from HA.     

Dielectric properties of strontium iron holmium niobate ceramics

Strontium iron holmium niobate (Sr(Fe_1?xHo_x)_0.5Nb_0.5O₃) ceramics were synthesized via a solid-state reaction technique. The undoped ceramic showed an orthorhombic phase, but it transformed to a pseudocubic phase for higher Ho concentrations. A low solubility limit of Ho in SFN caused a formation of second phase for the x=0.15 ceramic. Dielectric behavior of undoped ceramic exhibited high dielectric constant over a wide temperature range. However, the doping shifted this region to a higher temperature. The doping also shifted the peak of dielectric loss to a higher temperature. Activation energy of dielectric relaxation increased with increasing Ho concentration. In addition, complex impedance analysis was applied to determine the behaviors of grain boundary and grain after doping.     

Effect of composition and grain size on dielectric,ferroelectric and induced strain behavior of PLZT/ZrO2 composites

Lead lanthanum zirconate titanate ceramics (PLZT) are well known for their excellent dielectric, piezoelectric and ferroelectric properties. In this study, PLZT 9/70/30, 9/65/35 and 9/60/40 ceramics were prepared by vibro-milling mixed-oxide method. All compositions of powders were uniaxial pressed in pellets and sintered at the temperatures of 1200–1275 °C with various soaking times of 2, 4 and 6 h. The X-ray diffraction (XRD) patterns confirmed that all the PLZT samples had perovskite structure with ZrO₂ as a second phase and PLZT/ZrO₂ composite structure was formed. Dielectric behavior at the frequency of 1 kHz showed broad peak indicating relaxor ferroelectric behavior and the difference of the temperature at maximum dielectric at different frequencies increased when Zr:Ti ratio increased. Polarization with electric field (P-E loop) at room temperature showed that when Zr:Ti ratio increased, the coercive field decreased resulting from crystal structure change from tetragonal to rhombohedral. Induced strain with electric field depended on microstructure where the value of S_max/E_max tended to decrease with increasing grain size. It can be concluded that dielectric and ferroelectric behavior predominantly depended on composition of PLZT ceramics and induced strain behavior predominantly depended on grain size of PLZT ceramics.     

The effect of heat treatment temperature on phase formation and luminescence properties of calcium magnesium silicate glass-ceramics doped with Sm2O3

Abstract

The transparent glasses of CaO-MgO-Al₂O₃-SiO₂-ZnO system doped with Sm₂O₃ was prepared by conventional melt-quenching method. The obtained glasses were heat treated at a suitable temperature (875?°C–920?°C for 2?h) identified by differential thermal analysis (DTA). Phase formation and microstructure of glass-ceramics were characterized by X-ray diffraction and scanning electron microscopy, respectively. The optical transmission spectra were recorded by UV-Vis spectrophotometer in the wavelength range between 350 and 1000?nm. It was found that the increase in heat treatment temperature reduced the transparency of the glass-ceramics. The luminescence properties were identified by fluorescence spectroscopy. The excitation spectra of Sm₂O₃ doped CaO-MgO-Al₂O₃-SiO₂-ZnO glass-ceramic samples are in wavelength range of 550–750?nm and the emission spectra exhibited a strong orange-red luminescence composed of 562, 599 and 654?nm under excited at 402?nm. The results of XRD studies revealed the occurrence of diopside (CaMgSi₂O₆) and akermanite (Ca₂MgSi₂O₇) phases. The increasing of heat treatment temperature has no effect on the shift of emission spectra.