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In this study, lead zirconate titanate (Pb(Zr_0.44Ti_0.56)O₃) ceramics were fabricated with a mixed oxide synthetic route of lead oxide (PbO) and zirconium titanate (ZrTiO₄) precursors. The effects of sintering temperature on phase formation, densification and dielectric responses of the ceramics have been investigated using XRD, SEM, EDX and dielectric measurement techniques. The densification of the PZT ceramics with density of 97% theoretical density can be achieved with appropriate sintering condition without any sintering additives. The optimized sintering condition has been identified as 1225°C for 4 h. More importantly, the dielectric properties are found to improve with increasing sintering temperature and grain size. However, when sintered over 1250°C, the dielectric properties of the ceramics are seen to deteriorate as a result of PbO vaporization, ZrO₂ segregations and porosity.

Relatively low strength and fracture toughness of ceramics have restricted their applications. Various solutions have been studied to overcome the abovementioned drawbacks. One of the most sophisticated and promising solution is production of multilayer ceramic composites. High hardness, heat and wear resistance, low electrical and thermal conductivity, and resistance to chemical attacks are the most important characteristics of Al₂O₃. Therefore, it is a common candidate for various industrial applications. Multilayer alumina-zirconia composites were made using two methods of isostatic and hydraulic compaction of dry ceramic powders. The green articles were conventionally sintered at 1420, 1550 and 1650°C for 3h. The microstructure and density of composites were investigated. The results show that the pressing method and sintering temperature have a relatively moderate effect on the microstructure and density of the sintered samples.

(TiBw+TiCp)/Ti6Al4V composites were fabricated by reactive hot-pressing at the temperature range of 800~1200°C using the starting materials of TiB₂, C and Ti6Al4V powders. The XRD results suggested that the reaction between C and Ti happened 900°C and above, while the reaction between TiB₂ and Ti happen at 1100°C and above. SEM results also suggested that the reaction between C and Ti was prior to that between TiB₂ and Ti. With the increase of the sintering temperature, the size of TiC particle and TiB whisker reinforcements increased gradually. The TiC particle was formed at the boundaries of original Ti6Al4V particles, while the TiB whiskers grew toward the inside of Ti6Al4V particles, which resulted in a strong bonding between neighboring Ti6Al4V particles. The results of hardness and relative density tests showed that the (TiBw+TiCp)/Ti6Al4V composites sintered at 1100°C had the highest hardness and relative density compared with that sintered at other temperatures.

Tungsten and copper, two metals of complete mutual immiscibility, show a variety of densification behaviors due to the processing condition in the sintering stage. In this regard, the presence of different impurities during the densification process, have different influences on the consolidation of the primary powder. In this work, the effects of impurities introduced to the powder by the precursor salt in a novel thermo-chemical homogeneous co-precipitation method were investigated. Addition of sodium tungstate to the aqueous solution of copper nitrate saturated in aqueous ammonia solution, will result in precipitation of CuWO₄·2H₂O which will float in a mass of wandering Na⁺ ions in the solution. Removal of these sticking ions by multi stage washing has a certain effect on the final density of the sintered powder. The density of the sintered product was evaluated both with and without the removal of the Na and the mechanism by which this impurity deteriorates the densification was discussed in this work.

Three various α-alumina nanopowders have been characterized and their behavior in dry uniaxial pressing followed by pressureless sintering in air investigated. Nearly full dense ceramic material has been obtained at no more than 1300°C and its grain size evaluated by scanning electron microscopy and X-ray line profile analysis as being about 200 nm. The most suitable powder for low temperature sintering was reported to be that consisting of aggregates strong enough to enable their dense packing during the die filling and early period of pressure rise but capable of being destroyed further at final stage of compaction. Several dense samples with grain size on the level of 100 nm and less have been shown to be available at 1150-1200°C if a proper molding technique would be developed.

According to both the first principle and materials chemistry, a method for fabricating [(Ca_1-xSr_x)_2-2y](Ti_2-2yLi_2y)Si_2yO_6-y ceramic was investigated. It was considered that the sintering was promoted by self-accelerated diffusion due to the formation of point defects caused by doping with Li₂Si₂O₅. Consequently, a concept of non-stoichiometrically activated sintering, which was enhanced by point defects without the help of a grain boundary phase, was systematically studied in the Ca_1-xSr_xTiO_3-Li₂Si₂O₅ system. The mechanical and dielectric properties of [(Ca_1-xSr_x)_2-2y](Ti_2-2yLi_2y)Si_2yO_6-y were greatly enhanced by adding Li₂Si₂O₅. To improve CO₂ decomposition activity, [(Ca_1-xSr_x)_2-2y](Ti_2-2yLi_2y)Si_2yO_6-y, which possesses both high permittivity and high dielectric strength was used as a dielectric barrier to decompose CO₂ by dielectric barrier discharges (DBDs) plasma without using any catalyst and auxiliary substance. It successfully generated DBDs plasma and the CO₂ conversion was much higher than that using an alumina or a silica glass barrier which was widely used as the dielectric barrier in previous studies.

Samples of CaCu₃Ti₄O₁₂ (CCTO) ceramics were prepared by solid state reaction method. X-ray diffraction analysis confirmed single phase formation for the powder calcined at 1173 K. Sintering was done at different temperatures viz. 1348 K, 1373 K and 1398 K with a fixed heating rate of 3 K/min. Detailed study of dielectric properties was carried out for the CCTO samples sintered at 1373 K for different duration of holding times (2 h and 10 h). It is found that dielectric properties are sensitive to both sintering time and temperature. With increasing sintering time from 2 h to 10 h dielectric constant increases from ∼2.1 × 10⁴ to ∼2.5 × 10⁴ measured at 1 kHz at room temperature. Impedance spectroscopy has been used for separating out of grain and grain boundary contributions to the overall electrical properties.

Ba₄LaTi_0.3Sn_0.7O₁₅ ceramic was prepared through conventional solid state mix oxide route followed by characterization using X-ray diffraction (XRD) and scanning electron microscope (SEM) for phase and microstructural investigation. The dielectric properties at low and microwave frequencies were measured using LCR meter and vector network analyzer. XRD results revealed single phase ceramics and the microstructure was comprised of compact grains with size ranging from 4–12 μm. The lattice parameters refined by the least squares method were a = b = 5.7680(2) Å, c = 11.7491(6) Å, V = 337.81 ų and Z = 1. Optimum properties i.e., ε_r~44.6, Q_uf_o~15, 500 GHz and τ_f~2.05 ppm/°C were achieved for Ba₄LaTi_0.3Sn_0.7 Nb₃O₁₅ ceramic sintered at 1475°C for 4 h.

Microwave (MW) dielectric ceramics in (1 - x)(Li_1/2Nd_1/2)TiO₃–xCaTiO₃ (0.2 ≤ x ≤ 0.8) composition were prepared through the conventional solid-state reaction. X-ray diffraction (XRD) analysis and scanning electron microscopy (SEM) combined with energy dispersive X-ray analysis (EDX) indicated that the matrix phase was a continuous solid solution with orthorhombic perovskite structure. A minor amount of secondary phase was detected only in the composition of x = 0.7 and 0.8. The (1 - x)(Li_1/2Nd_1/2)TiO₃–xCaTiO₃ ceramics showed a very high permittivity of 118–153 and reasonable Q × f₀ values of 2360–5930 GHz as x increased from 0.2 to 0.8. The temperature coefficient of resonant frequency (τ_f) of the samples increased with increasing x value and was approximately linearly proportional to ε_r. Bi₄B₂O₉ addition effectively tailored the τ_f of (1 - x)(Li_1/2Nd_1/2)TiO₃–xCaTiO₃ ceramics to near zero at low temperature, and induced no degradation of Q × f₀ value. The x = 0.3 composition with 20 wt.%Bi₄B₂O₉ addition sintered at 1050°C exhibited dielectric properties of ε_r = 112.4, Q × f₀ = 2414 GHz and τ_f = 8.9 ppm/°C.

Particle coalescence has wide applications in nature and industry. In this study, molecular dynamics (MDs) simulations were employed to examine the sintering of Cu and Au nanoparticles, as well as two other systems, namely, Cu nanoparticles and Au nanoparticles. The results suggested that, the Au atoms diffused through the outer area of the sintering neck before the nanoparticles were fused into one sphere. The possible reason was that the Au atoms resembled fluid, which could be ascribed to the local thermal energy at the contact area. Typically, the change in energy per atom from 300 K to the contact temperature denoted that less energy was required for the atoms in the pure Cu system to contact with each other than those in the other two systems.

Porous Ni–Ti alloys were fabricated by reactive synthesis of Ni and Ti elemental powders. The corrosion behavior of porous Ni–Ti alloys was explored by electrochemical methods and weight change measurements at 298 K in seawater. The polarization curves and electrochemical impedance spectroscopy data show that porous Ni–Ti (6.5:3.5) alloys provide the best corrosion resistance. The values of corrosion current density and corrosion rate are 1.6944 × 10⁻⁴ mA/cm² and 1.9929 mm/a, respectively. The corrosion behavior and corrosion mechanism of porous Ni–Ti alloys are also discussed.

The effect of a small amount of Sb doping (5%) on the formation of the high temperature superconducting phase has been investigated on the Bi_1.5Pb_0.5Sr₂Ca₂Cu₃O_y compound. It is observed that at 860°C the T_c zero value depends on the sintering time. It first increases to a maximum value of 96 K and then decreases to a stable lowest value of 88 K. The samples have been characterized by X-ray diffraction (XRD), four probe electrical resistance and current density measurements. The XRD revealed the presence of two phases: an orthorhombic high-T_c 2223 phases with lattice constants a = 5.395 Å, b = 5.508 Å, c = 37.0422 Å and another tetragonal low-T_c 2212 phase with lattice constants a = b = 5.419 Å, c = 30.832 Å.

Nanoparticles of samarium barium antimonate (Ba₂SmSbO₆), a complex perovskite has been synthesized using an auto-ignition combustion process for the first time. The nanoparticles thus obtained have been characterized using X-ray diffraction, thermo-gravimetric analysis, differential thermal analysis, Fourier transform infrared spectroscopy, scanning electron microscopy and transmission electron microscopy. The XRD studies have shown that the as-prepared powder is phase pure Ba₂SmSbO₆ and has a complex cubic perovskite (A₂BB'O₆) crystalline structure with lattice constant a = 8.491 Å. The particle size of the as-prepared powder was in the range 20–50 nm. The nano crystals of Ba₂SmSbO₆ synthesized by the combustion technique could be sintered to 97% of the theoretical density by heating at a temperature of 1550°C for 2 h. By the present combustion synthesis a phase pure Ba₂SmSbO₆ nanopowder could be obtained by a single step process without the need of any calcination step.

Here we report the investigations on Sm-substituted PZTFN (Pb_1-xSm_xZr_0.588Ti_0.392Fe_0.01Nb_0.01O₃) (where x = 0, 0.02, 0.04, 0.06, 0.08, 0.10) polycrystalline solid solutions fabricated by solid-state reaction method. XRD analysis shows all the samples to be single phase with tetragonal structure. Dielectric measurements were carried out in the temperature range 30°C–400°C at different frequencies in the range 100 Hz to 100 kHz. From the temperature variation of dielectric constant (ε), Curie temperature (T_C) was determined which was found to decrease with increasing x. The room temperature dielectric constant (ε_RT) initially increases with increasing x and then starts decreasing. Dielectric loss improves with Sm-doping.

This study aims to fabricate and characterize a series of new complex-structured ceramics with formula (1 - x)Pb(Zr_0.52Ti_0.48)O_3-xBi_3.25Dy_0.75Ti₃O₁₂ or (1 - x)PZT-xBDT (when x = 0, 0.1, 0.3, 0.5, 0.7, 0.9 and 1.0) using a solid state mixed oxide and sintering method. Optimum sintering temperature for this system was found to be 1000°C for 4 h dwell time. Phase analysis using X-ray diffraction indicated existence of BDT- as well as PZT-based solid solutions with corresponding lattice distortion. Scanning electron micrographs of ceramic surfaces showed plate-like structure in BDT-rich phase while typical grain structure was observed for PZT-rich phase. PZT-rich ceramics also possessed high densities due to their more equiaxed grains with high packing capability compared to the ceramics with addition of plate-shaped BDT.

We have examined superconducting property of MgB₂, containing Type 1 elemental superconductor, Pb. The results showed double transition temperatures of superconductivity. Although the addition of Pb considerably improved grain connectivity of MgB₂, the presence of Type I superconducting phase (Pb) degraded the superconductivity of composites by flux creep.

CaCu₃Ti₄O₁₂ (CCTO) ceramics were prepared by the solid-state reaction route. Effect of sintering time was studied on the polarization (P) versus electric field (E) behavior. Unlike conventional ferroelectric hysteresis loop, PE hysteresis behavior in CCTO ceramics was observed to exhibit ferroelectric-like loop where polarization does not saturate but gives a maximum value. Remnant polarization and maximum polarization was observed to increase with sintering time. Current (I)–voltage (V) characteristics shows a nonlinear behavior making them useful for varistor applications. Coefficient of non-linearity (α) is also found to depend on sintering duration.

A gel was formed when an aqueous solution of BaCl₂, NbF₅ and citric acid in stoichiometric ratio is heated on a water bath at 100°C. This gel on decomposition at 700°C yielded the nano phase of BaNb₂O₆ as confirmed by X-ray diffraction study. The crystal structure is orthorhombic with unit cell parameter a = 12.2136 Å, b = 10.2413 Å, c = 7.8831 Å. The estimated grain size is 88 nm. Dielectric studies reveal the dielectric relaxation mechanism. Conducting charges and free charges both contribute to the dielectric relaxation in this material. Electrical properties of the material were studied using impedance spectroscopy technique. Detailed analysis of impedance spectrum suggested that the electrical properties are strongly temperature-dependent. The relaxation is polydispersive and conduction is mainly through grains. AC conduction activation energies are estimated from Arrheneus plots and conduction mechanism is discussed.

Lead zirconate titanate (PZT) is one of the most important piezoelectric materials widely used for underwater sensors. However, PZTs are hard and non-compliant and hence there is an overwhelming attention devoted toward making it flexible by preparing films on flexible substrates by different routes. In this work, the electrochemical deposition of composition controlled PZT films over flexible stainless steel (SS) foil substrates using non-aqueous electrolyte dimethyl sulphoxide (DMSO) was carried out. Effects of various key parameters involved in electrochemical deposition process such as current density and time of deposition were studied. It was found that a current density of 25 mA/cm² for 5 min gave a good film. The morphology and topography evaluation of the films was carried out by scanning electron microscopy (SEM) and atomic force microscopy (AFM), respectively, which showed a uniform morphology with a surface roughness of 2 nm. The PZT phase formation was studied using X-ray diffraction (XRD) and corroborated with Raman spectroscopic studies. The dielectric constant, dielectric loss, hysteresis and I–V characteristics of the film was evaluated.

In this study, ZnO nanoparticles and MnO-doped SnO₂-based thick film varistors (TFVs) were fabricated using screen printing technique. The sintering temperature had significant impact on the SZM-based TFVs, especially in terms of grain growth, even at a low sintering temperature of 1100${}^{\circ }$C. The strong solid-state reaction during sintering may be attributed to the large surface area of the 20 nm ZnO nanoparticles that promoted strong surface reaction even at low sintering temperatures. Moreover, the X-ray diffraction lattice constant and full wave at half maximum data indicated that the sintering process also improved the grain crystallinity with the decrease in intrinsic compressive stress. The sintering temperatures also significantly influenced the electrical properties of the SZM-based TFVs with a significant decrease in the breakdown field from 360 V/mm (sample at 1100${}^{\circ }$C) to 158 V/mm (sample at 1250${}^{\circ }$C). The grain boundary resistance ($R_{\mathrm{\text{GB}}})$ also experienced a dramatic drop from 266.4 k$\mathrm{\Omega }$ (sample at 1100${}^{\circ }$C) to 89.46 k$\mathrm{\Omega }$ (sample at 1250${}^{\circ }$C). The sample sintered at 1200${}^{\circ }$C exhibited superior electrical behaviors with a nonlinear exponent of 61 and leakage current of 115 $\mu$A. Furthermore, it achieved high permittivity and low dissipation factor at the low frequency range. The conduction behaviors of ${\mathrm{\text{O}}}^{\prime }$ ions with activation energy of approximately 0.6 eV was dominated by decreasing ${\mathrm{\text{Zn}}}_{\mathrm{\text{Sn}}}^{\prime \prime }$ and ${\mathrm{\text{Mn}}}_{\mathrm{\text{Sn}}}^{\prime \prime }$ defects (around 0.4 eV) with increasing sintering temperature. Therefore, the sintering process can be applied to control the conduction behaviors of SZM-based TFVs doped with ZnO nanoparticle powder and achieve improved structural and electrical properties with good nonlinear behaviors.