Effect of PMN modification on structure and electrical response of xPMN–(1−x)PZT ceramic systems

The structural and electrical properties of xPb(Mg_1/3Nb_2/3)O₃–(1−x)Pb(Zr,Ti)O₃ ternary ceramic system with the composition near to the morphotropic phase boundary (MPB) and of xPb(Mg_1/3Nb_2/3)O₃–(1−x)Pb(Zr_0.47Ti_0.53)O₃ ceramics were investigated as a function of the Pb(Mg_1/3Nb_2/3)O₃ (PMN) content by scanning electron microscopy (SEM), X-ray diffraction (XRD), dielectric and piezoelectric spectroscopy and polarization-electric field measurement technique. Studies were performed on the samples prepared by a columbite precursor method for x=0.125, 0.25 and 0.5. Room temperature SEM investigations revealed common trends in the grain structure with increasing PMN content. XRD analysis demonstrated that with increasing PMN content in xPb(Mg_1/3Nb_2/3)O₃–(1−x)Pb(Zr_0.47Ti_0.53)O₃, the structural change occurred from the tetragonal to the pseudocubic phase at room temperature. Changes in the dielectric and ferroelectric behavior were then related to these structural trends and further correlated with the piezoelectric properties. The results of ferroelectric hysteresis measurements, in conjunction with dielectric spectroscopy, demonstrated an intermediate, relaxor-like behavior between normal and relaxor ferroelectrics in the solid solution system, depending on the PMN content.     

Mullite–Cobalt (II,III) Oxide System: Preparation of Ceramic Pigment Using Recycling of Fly Ash

Silicon - The present work depends on recycling of fly ash by preparation of stoichiometric mullite containing various amounts of Co3O4; 0, 5, 10, 15 wt.% to obtain pigment ceramic materials. The...     

Fullerene (C60)–transitional metal (Ti) composites: Structural and biological properties of the thin films

Thin films of the binary C₆₀/Ti composites (with various phase ratios) were deposited on the Si(001) wafers and microscopic glass coverslips in continuous and micropatterned forms. The composites acquired a nanogranular structure with granules of about 50 nm in size. The RBS inspection confirmed homogeneous distribution of the phases and also the presence of oxygen. The Raman study suggested polymerization of the C₆₀/Ti composites into polymeric structures. The hybrid substrates were tested on biocompatibility—the films were seeded with human osteoblast-like MG 63 cells, and their proliferation was analyzed for 7 days. It has been found that the C₆₀/Ti composites can be counted as good supports for the adhesion of the selected MG 63 cells. The composites exhibited similar biocompatibility as the mix of amorphous carbon and titanium, but different than fullerene (C₆₀) solids.     

Sintering of powders in the CrSi2–Ti(Ta)Si2 systems depending on the methods for synthesis

Composite materials based on refractory silicides, in particular their solid solutions, are widely used in many areas of engineering for parts of heating elements and heat resistance protective coatings. This paper presents the findings obtained in the study of peculiarities of solid-phase interaction during synthesis of Cr_0.9Ta_0.1Si₂ and Cr_0.5Ti_0.5Si₂ solid solutions depending on the synthesis conditions. The effect of the powder dispersity on compaction of targets from Cr_0.9Ta_0.1Si₂ and Cr_0.5Ti_0.5Si₂ powders has been studied, and it has been established that the use of nanosized powders complicates the process of pressing. Also, sintering of targets from nanosized Cr_0.9Ta_0.1Si₂ and Cr_0.5Ti_0.5Si₂ powders was studied. The sintered targets were established to have a small grain size and uniform porosity all over the volume. Thanks to small closed porosity, the targets exhibit high heat resistance under thermal shock.     

Effect of FeAl3 on properties of (W,Ti)C–FeAl3 hard materials consolidated by a pulsed current activated sintering method

Using a pulsed current activated sintering (PCAS) method, the densification of (W,Ti)C and (W,Ti)C–FeAl₃ hard materials was accomplished within 3 min. The advantage of this process is not only rapid densification to near theoretical density, but also prevention of grain growth in nano-structured materials. Highly dense (W,Ti)C and (W,Ti)C–FeAl₃ with a relative density up to 99% were obtained within 3 min by PCAS under a pressure of 80 MPa. The average grain size of the (W,Ti)C was less than 100 nm. Hardness and fracture toughness of the dense (W,Ti)C and (W,Ti)C–FeAl₃ produced by PCAS were also investigated. The fracture toughness and hardness values of (W,Ti)C, (W,Ti)C–5 vol.% FeAl₃, and (W,Ti)C–10 vol.% FeAl₃ consolidated by PCAS were 7.5 MPa m^1/2 and 2650 kg/mm², 10.5 MPa m^1/2 and 2480 kg/mm², 11 MPa m^1/2 and 2300 kg/mm², respectively.     

Structural,morphological, and magnetic characterization of bulk and thin films Y3Al5–xFexO12 (YAIG): From the perspective of aqueous sol–gel processing

An aqueous sol–gel method was used for the preparation of bulk Y₃Al_5–xFe_xO₁₂ (yttrium aluminum–iron garnet, YAIG) with the composition of x?=?0.0, 1.0, 2.0, 2.5, 3.0, 4.0, 5.0 and thin films with the composition of x?=?0, 3.0, 4.0, 5.0. The dip-coating technique was used for the preparation of Y₃Al_5–xFe_xO₁₂ films on a silicon (Si) substrate. The phase composition and surface morphology of both bulk and coatings were determined and compared. The synthesized powder samples were investigated by X-ray diffraction analysis, infrared spectroscopy, scanning electron microscopy, and Mössbauer spectroscopy. The data provide evidence that some sol–gel-derived powder specimens consist of magnetically ordered component, while others show paramagnetic behavior depending on the composition of the product. It was also shown that sol–gel processing route could be successfully used for the preparation of mixed-metal YAIG thin films.     

Influence of post-deposition annealing on electrical and optical properties of (Ta2O5)1-x - (TiO2)x thin films,x ≤ 0.08

Tantalum (Ta) and titanium (Ti) metal targets were direct current (DC) magnetron sputtered in the oxygen environment by varying its relative areas to deposit (Ta₂O₅)_1-x- (TiO₂)_x (TTO_x) thin films, with x = 0, 0.03, 0.06, and 0.08, onto the boron-doped p-silicon (1 0 0) and optically polished quartz substrates, at room temperature; and were annealed at 500, 600, 700, and 800 °C, for 1.5 h. The thin films annealed at and above 600 °C show the Ta₂O₅ structure. The leakage current density and capacitance-voltage (C–V) characteristics were measured for TTO_x, x ≤ 0.08, assisted Ag/TTO_x/p-Si metal– oxide– semiconductor (MOS) structures. The leakage current density was found minimum, for the films annealed at 800 °C, for all the prepared TTO_x films, x ≤ 0.08. The minimum leakage current density 1.6 × 10^?8 A/cm², at 3.5 × 10⁵ V/cm electric field, was observed for x = 0.03, annealed at 800 °C, among the prepared compositions. The prepared TTO_0.03 films, annealed at 700 °C show maximum dielectric constant 39, at 1 MHz. The optical parameters, viz., refractive index (n), extinction coefficient (k), and optical band gap (E_g) of the films, with x = 0.03, prepared on quartz substrates, were determined from their optical transmittance plots. The values of n and k of the crystalline films were observed increasing from 2.123 to 2.143, and 0.099 to 0.130, respectively, at 550 nm wavelength; and E_g decreasing from 3.95 to 3.89 eV with the increasing annealing temperature, from 600 to 800 °C. Ohmic emission, in the lower electric field; Schottky and space-charge- limited current conduction mechanisms, in the intermediate to higher electric fields, were generally envisaged from the current-voltage characteristics in the prepared Ag/TTO_0.03/p-Si structures.     

Corrosion behavior of calcium–magnesium–aluminosilicate (CMAS) on sintered Gd2SiO5 for environmental barrier coatings

The Gd₂SiO₅ performed high-temperature corrosion behavior on calcium–magnesium– aluminosilicate (CMAS) for environmental barrier coatings (EBCs). The synthesized Gd₂O₃-SiO₂ powder was prepared to fabricate a sintered Gd₂SiO₅ by spark plasma sintering (SPS) at 1400°C for 20 min. CMAS was sprinkled on the sintered Gd₂SiO₅ surface and exposed for 2, 12, and 48 h at 1400°C by isothermal heat treatment. The main corrosion factor is Ca, and Ca₂Gd₈(SiO₄)₆O₂ phase is formed by reacting with Gd₂SiO₅. Extended morphology of Ca₂Gd₈(SiO₄)₆O₂ particles observed in the reaction area become thicker as the heat treatment time increases as the CMAS is dissolved. According to the results of high-temperature X-ray diffraction (HT-XRD) and differential scanning calorimetry (DSC), CMAS melted at 1243°C or a higher temperature formed the reaction area. The Ca₂Gd₈(SiO₄)₆O₂ phase was recrystallized and grown due to the reaction of Gd₂SiO₅ and Ca of the CMAS components.     

Electrophoretic deposition of Pb(Ni1/3Nb2/3)O3–Pb(Zr,Ti)O3 thick film on Pt wire

0.2PbNi_1/3Nb_2/3–0.8Pb(Zr,Ti)O₃ (PNN–PZT) thick films were deposited on Pt wire with the diameter of 50 μm by electrophoretic deposition (EPD) method. The EPD deposition times on the microstructures of PNN–PZT thick films were investigated. By optimizing the EPD process, the Pt wire can be uniformly wrapped with the PNN–PZT powders. During the sintering process, the as-deposited PNN–PZT/Pt wires were buried in the mixed powders of PbCO₃ and ZrO₂, and then sintered in the optimal temperature to get a dense microstructure. The piezoelectric properties of the thick films were characterized by scanning force microscopy (SFM) method. The results show that the PNN–PZT thick films prepared by EPD method have good piezoelectricity.     

Sintering behaviour and microwave dielectric properties of MgO–2B2O3–xwt％BaCu(B2O5)–ywt％H3BO3 ceramics

This study investigates the bulk density, sintering behaviour, and microwave dielectric properties of the MgO–2B2O3 series ceramics synthesised by solid-state r...     

The role of MgO on the structural properties of CaO–Na2O(MgO)–P2O5–CaF2–SiO2 derived glass ceramics

The effect of increasing MgO/Na₂O replacements (on mole basis) on the crystallization characteristics of glasses based on the CaO–Na₂O(MgO)–P₂O₅–CaF₂–SiO₂ system were studied by using DTA, XRD, and SEM. The crystallization characteristics of the glasses, the type of crystalline phases formed and the resulting microstructure were investigated. The main crystalline phases formed after controlled heat-treatment of the base glass were diopside, wollastonite solid solution, fluoroapatite and sodium calcium silicate phases. The increase of MgO at the expense of Na₂O led to decrease the amount of sodium calcium silicate phase. The Vicker's microhardness values (5837–3362 MPa) of the resulting glass–ceramics were markedly improved by increasing the MgO-content in the glasses. The obtained data were correlated to the nature and concentration of the crystalline phases formed and the resulting microstructure.     

Effect of Process Parameters on Microstructure and Mechanical Properties of Al-11.5%Si-1%Mg/bimodal SiC(m–n)composites

Silicon - Bimodal size SiC particles reinforced Al-Si alloy composites were fabricated by powder metallurgy route. Three different bimodal reinforcements with various volume fractions of micro and...     

Syntheses,structures and photoluminescence of Ln(III)–Cu(I) coordination polymers based on benzimidazole-5-carboxylate and oxalate ligands

Three novel Ln(III)–Cu(I) coordination polymers, namely [LnCu(Hbic)₃(ox)_0.5] [Ln = Sm (1), Dy (2), Hbic = benzimidazole-5-carboxylate, ox = oxalate] and [EuCu(Hbic)₂(ox)H₂O]·2H₂O (3) have been hydrothermally synthesized and stucturally characterized. Both complexes 1 and 2 display the same unusual 2D layer heterometallic coordination frameworks that are built up by dimeric [Ln₂(Hbic)₆] cores and oxalate ligands by sharing Cu(I) ions. Complex 3 represents 1D polymeric chain architecture constructed from Eu₂Cu₂ ring units and oxalate ligands. Furthermore, the luminescent property of complex 3 has also been investigated.     

Effects of Water and Ion-Exchanged Counterion on the FTIR Spectra of ZSM-5. II. (Cu+–CO)-ZSM-5: Coordination of Cu+–CO Complex by H2O and Changes in Skeletal T–O–T Vibrations

The 2157 cm^–1 (strong) and 2108 cm^–1 (very weak) (CO) IR bands due to Cu⁺–CO in ZSM-5 zeolite with ¹²C and ¹³C isotopes, respectively, are reversibly red-shifted by subsequent adsorption of H₂O at 293 K. On the contrary, the locally perturbed internal (T–O–T) asymmetric stretching framework vibration [ _as ^int (TOT)(Cu⁺–CO)=965 cm^–1] is reversibly blue-shifted. The courses of the band shifts revealed notable features. Charge transfers from water to Cu⁺ ions, changes in coordination spheres of Cu⁺(CO)(H₂O) _n aqua complexes and secondary (solvent-like) effects were considered to explain the results.     

Effect of plastics substrate on phase separation behavior and adhesion for RSi(OC2H5)3–Si(OC2H5)4 coatings prepared by sol–gel process

Three functional siliconalkoxides (RSi(OC₂H₅)₃, RTES), phenyltriethoxysilane (PhTES), methyltriethoxysilane (MeTES), and 1,4-bis(triethoxysilyl)benzene (BTEB)–tetraethoxysilane (Si(OC₂H₅)₄, TEOS) coatings [xA?(100?x)TEOS (x=0–80, mol%), A=PhTES, MeTES, BTEB] were prepared by sol–gel process, and the effects of plastics substrates on both the distribution of organic component in the coatings and its adhesion on plastics substrates were discussed. Polyethylene terephthalate (PET) and polycarbonate (PC) with phenyl group and polyethylene (PE), polypropylene (PP) and polyvinylchloride (PVC) without phenyl group were employed as plastics substrates. The distribution of organic component was monitored by total reflection (ATR) fourier transform infrared (FTIR) measurements. Before the solidification of the coating sol, the organic component for good adhesion migrated on coatings/substrate interface side by the interaction between organic component and substrate. This interaction may be caused by π/π electron interaction, CH₃/π electron interaction and CH₃/CH₃ van der Waals interaction. The migration of phenyl group on plastics substrate with phenyl group was larger than that on plastics substrate without phenyl group, while the migration of methyl group on plastics substrate without phenyl group was larger than that on plastics' substrates with phenyl group. Thus, the chemical structure of substrate affected phase separation behavior in the coatings. Adhesion of PhTES–TEOS and BTEB–TEOS coatings on PET and PC increased drastically at larger than x=60. On the other hand, no adhesion was observed for all the MeTES–TEOS coatings.     

Effects of rapid thermal annealing treatment on 0·95(Na0·5Bi0·5)TiO3-0·05BaTiO3 thin films

Abstract

Abstract

A 0·95(Na_0·5Bi_0·5)TiO₃-0·05BaTiO₃+1?wt-%Bi₂O₃ (NBT-BT3) ceramic was used as target to deposit the NBT-BT3 thin films. The excess 1?wt-%Bi₂O₃ was used to compensate the vapourisation of Bi₂O₃ during the depositing processes. The optimal deposition parameters were substrate temperature of 500°C, radio frequency power of 100?W, chamber pressure of 10?mtorr and oxygen concentration of 40%. Rapid thermal annealing treated processes were carried out on NBT-BT3 thin films from 600 to 800°C in ambient or in oxygen atmosphere for 1?min. The surface morphologies and thicknesses of NBT-BT3 thin films were characterised by field emission scanning electron microscopy, and the thickness was ～216?nm. It would be shown that the NBT-BT3 thin films annealed in oxygen atmosphere had the smaller grain size, larger memory window, smaller leakage current density, larger remanent and saturation polarisation and smaller coercive field than the NBT-BT3 thin films annealed in ambient atmosphere.