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1.
The effects of sintering temperature (T sinter) and sintering time (t sinter) were investigated for Pb0·95Sr0·05(Zr0·53Ti0·47)O3 + x%wtCr2O3 system to determine the optimum regimen of sintering. The study was performed by determining the following parameters: relative density (ρ rel) and sintering rate $ (\dot \varepsilon _\rho ) $ (\dot \varepsilon _\rho ) . The grain size was diminished when small amounts of Cr2O3 were added to system and was enhanced when the sintering temperature and time was increased. The dielectric constant becomes maximum and the electric loss becomes minimum with the sintering temperature of 1290°C. The optimum regimen of sintering is T sinter = 1290°C during 70 min. The piezoelectric properties for the optimum regimen of sintering were studied.  相似文献   

2.
0.67Pb(Mg1/3Nb2/3)O3–0.33PbTiO3 (PMNT) ceramics were fabricated by using their powders synthesized through a sol–gel process. Excess Pb(CH3COO)2·3H2O (0, 2, 5, 10 or 15 mol%) was added to the starting materials to study the effect of excess Pb on the microstructures, ferroelectric and dielectric properties of the PMNT ceramics. All the X-ray diffraction peaks can be indexed using perovskite-type PMNT for the ceramics prepared with excess Pb, while the PMNT ceramics with no excess Pb contain a little pyrochlore phase. The PMNT ceramics prepared with 2 mol% excess Pb are dense and uniform and composed of grains ranging from 3 to 7 μm. They exhibit the largest remnant polarization (P r = 32.1 μC/cm2) and the highest peak dielectric constant (ε max = 12,725). When more than 2 mol% excess Pb added, the electrical properties of the PMNT ceramics decreased with increasing excess Pb. Too much excess Pb (over 10 mol%) resulted in abnormal grain growth (>20 μm), large pores and residual PbO in amorphous state in PMNT ceramics, and they impaired the ferroelectric and dielectric properties of PMNT ceramics greatly.  相似文献   

3.
Ho3+-modified Pb(Zn1/3Nb2/3)O3–9PbTiO3 (PZN–9PT) single crystals were grown through a flux method. Phase structure and microstructural morphology of the as-grown single crystals were performed by X-ray diffraction analysis and scanning electron microscopy. The refinement of the lattice parameters were obtained by the Rietveld method. The electrical properties of PZN–9PT single crystals were improved significantly by the modification of Ho3+ ions. The rhombohedral–tetragonal phase transition temperature, Curie temperature, coercive field at 15 kV cm?1, and remnant polarization of Ho3+-modified PZN–9PT single crystals were increased by 14, 42 K, 2.4 kV cm?1, and 7.5 μC cm?2, respectively (i.e., 375.45, 448.45 K, 5.9 kV cm?1, and 38.40 μC cm?2, respectively). Furthermore, Lorentz-type law was used to describe the dielectric relaxor behavior of the as-grown single crystals.  相似文献   

4.
CuAlO2 (CAO) thin films were prepared on quartz glass substrates by sol–gel spin-coating method. The effects of annealing temperatures, concentrations of sols and Al/Cu atomic ratios on structure, morphology and electrical properties have been investigated. It was found that CAO film with an Al/Cu atomic ratio of 0.8 approximately and the total metallic ion concentration of 0.7 M after heat treatment at 750 °C for 3 h in argon gas flow of 450 mL/min exhibited the lowest room temperature resistivity of 13.5 Ωcm.  相似文献   

5.
A series of Ca3−x Gd x Co4O9+δ precursor powders were synthesized by the polyacrylamide gel method, and their ceramics were obtained by the Spark Plasma Sintering (SPS). There were lots of defects in the sheet-like grains from SEM and TEM observations. The electrical and the thermal transport properties were obviously affected by the material microstructure. The small polaron hopping conduction mechanism was determined above 600 K, and the hopping activation energy increased with the increase of doping contents. It was found that the Seebeck coefficient and the resistivity of doped samples were markly enhanced due to the impurity compensation effect, and their thermal conductivities were decreased due to the defects scattering. The maximum figure of merit of ZT = 0.24 at 973 K was obtained for Ca2.7Gd0.3Co4O9+δ.  相似文献   

6.
The (1−x)Bi0·5(Na0·82K0·18)0·5TiO3−x LiSbO3 (x = 0−0·03) lead-free piezoelectric ceramics were fabricated by a conventional solid-state reaction method and the effect of LiSbO3 addition on microstructure and electrical properties of the ceramics was investigated. The results of XRD measurement show that Li+ and Sb5+ diffuse into the Bi0·5(Na0·82K0·18)0·5TiO3 lattices to form a solid solution with a pure perovskite structure. The LiSbO3 addition has no remarkable effect on the crystal structure. However, a significant change in grain size took place. Simultaneously, with increasing amount of LiSbO3, the temperature for a antiferroelectric to paraelectric phase transition clearly increases. The piezoelectric constant d 33 and the electromechanical coupling factor k p show an obvious improvement by adding small amount of LiSbO3, which shows optimum values of d 33 = 175 pC/N and k p = 0·36 at x = 0·01.  相似文献   

7.
A transparent electrode of β-Ga2O3 films for solar cells, flat panel displays and other devices, which consist in chemically abundant and ecological elements of gallium and oxygen, were grown on quartz or silicon substrates by RF magnetron sputtering using a sintered Ga2O3 target. The impurities of Si or Ge were also added into the grown films. The polycrystalline β-Ga2O3 grew by the thermal annealing after RF sputtering. Optical absorption measurements indicated that the grown β-Ga2O3 film after 600°C annealing have a band gap of about 5 eV.  相似文献   

8.
Films 150–200 nm in thickness, with the nominal composition Mg(Fe0.8Ga0.2)2O4 − δ have been grown on (100) single-crystal silicon substrates by ion-beam sputtering in vacuum. The effect of growth and annealing conditions on the crystal structure and morphology of the films has been studied, and the thermal conditions for the growth of spinel-structure films have been optimized.  相似文献   

9.
SrBi4Ti4O15 (SBTi) and Bi-excess and Sr-deficient SBTi (Sr-deficient SBTi, Sr0.8Bi4.13Ti4O15) thin films were deposited on Pt/Ti/SiO2/Si (100) substrates using a sol–gel method. Structure and electric properties were investigated systematically. These films were random oriented. The remnant polarization (2P r) of SBTi film was about 25.3 μC/cm2, which was larger than the reported value of SBTi thin film. The film with Sr-deficient and Bi-excess composition showed a very large remnant polarization of 36.6 μC/cm2. The capacitance–voltage (CV) characteristics of both the films showed normal ferroelectric behavior. The Curie temperatures of the same Sr-deficient and Bi-excess component ceramics sample increased slightly in comparison with that of SBTi. More importantly, the Sr-deficient and Bi-excess SBTi thin film showed high fatigue resistance against continuous switching up to 4.4 × 1010 cycles.  相似文献   

10.
Bi3.6Ho0.4Ti3O12 and (Bi0.9Ho0.1)4−x/3Ti3−x V x O12 (BHTV) (x = 0.3, 1.2, 3.0 and 6.0%) thin films were prepared on Pt/Ti/SiO2/Si substrates by sol–gel method. The effect of V content on their microstructure and ferroelectric properties were investigated. All the BHTV samples consisted of the single phase of Bi-layered Aurivillius phase. The B-site substitution with high-valent cation of V5+, in Bi3.6Ho0.4Ti3O12 films, enhanced the remanent polarizations (2Pr) and reduced the coercive field (2Ec). The BHTV film with x = 0.3% exhibited the better electrical properties with 2Pr 45.5 μC/cm2, 2Ec 257 kV/cm, good insulting behavior, as well as the fatigue-free characteristic.  相似文献   

11.
12.
ZrO2–SnO2 nanocomposite thin films were deposited onto quartz substrate by sol–gel dip-coating technique. Films were annealed at 500, 800 and 1,200 °C respectively. X-ray diffraction pattern showed a mixture of three phases: tetragonal ZrO2 and SnO2 and orthorhombic ZrSnO4. ZrSnO4 phase and grain size increased with annealing temperature. Fourier transform infra-red spectroscopy spectra indicated the reduction of –OH groups and increase in ZrO2–SnO2, by increasing the treatment temperature. Scanning electron microscopy observations showed nucleation and particle growth on the films. The electrical conductivity decreased with increase in annealing temperature. An average transmittance greater than 80 % (in UV–visible region) was observed for all the films. The optical constants of the films were calculated. A decrease in optical band gap from 4.79 to 4.59 eV was observed with increase in annealing temperature. Photoluminescence (PL) spectra revealed an emission peak at 424 nm which indicates the presence of oxygen vacancy in ZrSnO4. PL spectra of the films exhibited an increase in the emission intensity with increase in temperature which substantiates enhancement of ZrSnO4 phase and reduction in the non-radiative defects in the films. The nanocomposite modifies the structure of the individual metal oxides, accompanied by the crystallite size change and makes it ideal for gas sensor and optical applications.  相似文献   

13.
Nanocrystalline Co3O4 thin films were prepared on glass substrates by using sol–gel spin coating technique. The effect of annealing temperature (400–700 °C) on structural, morphological, electrical and optical properties of Co3O4 thin films were studied by X-ray diffraction (XRD), Scanning Electron Microscopy, Electrical conductivity and UV–visible Spectroscopy. XRD measurements show that all the films are nanocrystallized in the cubic spinel structure and present a random orientation. The crystallite size increases with increasing annealing temperature (53–69 nm). These modifications influence the optical properties. The morphology of the sol–gel derived Co3O4 shows nanocrystalline grains with some overgrown clusters and it varies with annealing temperature. The optical band gap has been determined from the absorption coefficient. We found that the optical band gap energy decreases from 2.58 to 2.07 eV with increasing annealing temperature between 400 and 700 °C. These mean that the optical quality of Co3O4 films is improved by annealing. The dc electrical conductivity of Co3O4 thin films were increased from 10−4 to 10−2 (Ω cm)−1 with increase in annealing temperature. The electron carrier concentration (n) and mobility (μ) of Co3O4 films annealed at 400–700 °C were estimated to be of the order of 2.4–4.5 × 1019 cm−3 and 5.2–7.0 × 10−5 cm2 V−1 s−1 respectively. It is observed that Co3O4 thin film annealing at 700 °C after deposition provide a smooth and flat texture suited for optoelectronic applications.  相似文献   

14.
The low-temperature heat capacity of Dy2O3 · 2ZrO2 and Ho2O3 · 2ZrO2 has been determined by adiabatic calorimetry in the temperature range 10–340 K. The results have been used to calculate the entropy, enthalpy increment, and reduced Gibbs energy of the zirconates without taking into account their low-temperature magnetic transformations.  相似文献   

15.
We describe atomic layer deposition of silica and alumina layers on GaAs, InAs, and InSb substrates. The conditions for layer-by-layer growth of surface nanostructures are established, and some of their dielectric parameters are evaluated.  相似文献   

16.
BaO–B2O3–SiO2–Al2O3 (BBSA) glass/silica composites synthesized by solid-state reaction method were developed for CBGA packages, and the effects of sintering temperature (900–950 °C) on the phase transformation, microstructure, thermal, mechanical and electrical properties were investigated. XRD results show that the major phases quartz and cristobalite, and the minor phase BaSi2O5 are detected in BBSA composites. Furthermore, it was found that the quartz phase transforms to cristobalite phase at 930–940 °C. The formation of cristobalite phase with higher coefficient of thermal expansion (CTE) led to the increase of CTE value of BBSA composites. However, excessive cristobalite phase content would degrade the mechanical properties and the linearity of thermal expansion of the ceramics. BBSA composites sintered at 920 °C exhibited excellent properties: low dielectric constant and loss (εr = 6.2, tanδ = 10?4 at 1 MHz), high bending strength (179 MPa), high CTE (12.19 ppm/°C) as well as superior linearity of the thermal expansion.  相似文献   

17.
Pb(Zr0·52Ti0·48)O3 (PZT) powders were prepared by hydrothermal method. The effects of experimental parameters, including Pb/(Zr, Ti) ratio, alkaline concentration, reaction temperature and time on the product powders were studied in detail. Pure PZT powders were synthesized at suitable experimental conditions and Raman spectra confirmed the PZT with a perovskite-type structure. The homogeneous PZT powders with cubic-shaped morphology were formed at alkaline concentration of 1·2 M after reacting at 230°C for 2 h. The pure PZT powders obtained at low temperature and low alkaline concentration were attributed to precursors, TiCl4, with high activity and mineralizer NaOH with small cation radius.  相似文献   

18.
The influences of Bi substitution on microwave dielectric properties of Ba4(La0.5Sm0.5)9.33Ti18O54 solid solutions were investigated. Dielectric ceramics with general formula Ba4(La(0.5−z)Sm0.5Bi z )9.33Ti18O54, z = 0.0–0.2 were prepared by conventional solid state route. The structural analysis of all the samples was carried out by X-ray diffraction and scanning electron microscopy. The dielectric properties were investigated as a function of Bi contents using open-ended coaxial probe method in the frequency range 0.3–3.0 GHz at room temperature. Dielectric constant varies from 83 to 88 and loss tangent from 2.1 × 10−3 to 5.5 × 10−3 at 3 GHz with temperature coefficient of resonant frequency changing from 106.7 to −8.4 ppm/oC as Bi contents increases from z = 0.00–0.20. It has been found that dielectric constant and temperature coefficient of resonant frequency improve whereas loss tangent is adversely affected with increase in Bi substitution.  相似文献   

19.
FTIR spectroscopy has been employed to investigate the structure of CaF2–B2O3 glasses. It is proposed that CaF2 partially modifies the borate network forming \textCa 1 / 2 2+ [\textBO 3 / 2 \textF] - {\text{Ca}}_{ 1 / 2}^{ 2+ } [{\text{BO}}_{ 3 / 2} {\text{F]}}^{ - } units. The rest of CaF2 is assumed to build an amorphous network formed of CaF4 tetrahedra. Analysis of density and molar volume revealed that the volume of CaF4 tetrahedron in the studied glasses is slightly greater than that in the crystalline form. Data of density, molar volume, and electric conductivity have been correlated with the glass structure. As far as the authors know, CaF2–B2O3 glasses are investigated for the first time.  相似文献   

20.
The properties of the composite, having a complicated microstructure, are decided by many factors such as those of glass matrix, crystal phases, fillers, and holes. We investigated how the addition of ceramic fillers to the glass matrix affects the mechanical and etching properties of the glass composite by forming new crystal phases. Different amounts of two fillers, ZnO and Al2O3, were added to a glass frit consisting of Bi2O3–ZnO–B2O3. It was sintered at 550 °C for 30 min. Based on the results of this study, the porosity and degree of crystallization of the composites could be controlled by adjusting the content of the ZnO and Al2O3 fillers. Therefore, porosity and degree of crystallization formed by the reaction between a glass matrix and fillers influence the mechanical and etching properties of the composite.  相似文献   

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