scholarly journals Nonstoichiometry Effects in SrTiO3 Ceramics Assessed by Transmission Electron Microscopy

2008 ◽  
Vol 14 (S3) ◽  
pp. 5-6 ◽  
Author(s):  
L. Amaral ◽  
A.M.R. Senos ◽  
P.M. Vilarinho
Keyword(s):  
Grain Size ◽  
Electrical Properties ◽  
Dielectric Permittivity ◽  
Grain Boundaries ◽  
Small Variation ◽  
Sintered Ceramic ◽  
Transmission Electron ◽  
Perovskite Type ◽  
Srtio3 Ceramics ◽  
Perovskite Type Structure

Strontium titanate (SrTiO3, ST) has a perovskite type structure that is cubic at room temperature, but transforms into a tetragonal one at 105K. At very low temperatures, ST exhibits an extremely large dielectric permittivity and piezoelectric and superconducting characteristics. ST finds applications in tunable microwave devices, due to a dependence of its dielectric response on the electric field and low microwave losses. ST electrical properties are strongly dependent on grain boundaries features and directly influenced by grain size distribution. It was found in our previous studies that a small variation in the stoichiometry of ST has a significant effect on the grain size of the sintered ceramic and related electrical properties: increased grain size and dielectric permittivity values have been reported for Ti excess compositions whereas Sr excess caused a decrease of grain size and of the dielectric permittivity. The tailoring of the dielectric properties by small non-stoichiometric variations in ST needs, however, a full understanding of its effects on the microstructure, phases structure and on the structure / composition of the grain boundaries.

scholarly journals Structural and Electrical Studies on ZnO-Based Thin Films by Laser Irradiation

2016 ◽  
Vol 2016 ◽  
pp. 1-6 ◽  
Author(s):  
Shanyue Zhao ◽  
Yinqun Hua ◽  
Ruifang Chen ◽  
Jian Zhang ◽  
Ping Ji
Keyword(s):  
Thin Films ◽  
Grain Size ◽  
Electrical Properties ◽  
Grain Boundaries ◽  
Laser Irradiation ◽  
Nonlinear Coefficient ◽  
Acceptor State ◽  
Xrd Pattern ◽  
Electrical Studies ◽  
Structural And Electrical Properties

The effects of laser irradiation on the structural and electrical properties of ZnO-based thin films were investigated. The XRD pattern shows that the thin films were highly textured along thec-axis and perpendicular to the surface of the substrate. Raman spectra reveal that Bi2O3segregates mainly at ZnO-ZnO grain boundaries. After laser irradiation processing, the grain size of the film was reduced significantly, and the intrinsic atomic defects of grain boundaries and Bi element segregated at the grain boundary were interacted frequently and formed the composite defects of acceptor state. The nonlinear coefficient increased to 24.31 and the breakdown voltage reduced to 5.34 V.

Pb-DOPING EFFECTS ON THE DIELECTRIC AND PYROELECTRIC PROPERTIES OF (Sr,Pb)TiO3 SYSTEM

2012 ◽  
Vol 02 (01) ◽  
pp. 1250005 ◽  
Author(s):  
Y. P. JIANG ◽  
X. G. TANG ◽  
Y. C. ZHOU ◽  
Q. X. LIU
Keyword(s):  
Dielectric Permittivity ◽  
Frequency Dispersion ◽  
X Ray Diffraction ◽  
Pyroelectric Properties ◽  
Doping Effects ◽  
Pyroelectric Sensors ◽  
Diffraction Patterns ◽  
Perovskite Type ◽  
Pb Doping ◽  
Perovskite Type Structure

Lead strontium titanate ( Sr 1-x Pb x) TiO 3 (0.20 ≤ x ≤ 0.45,step = 0.05) ceramics were prepared by conventional mixed oxide method. The X-ray diffraction patterns indicate that the prepared samples have perovskite-type structure. With the increase of Pb content, there is a tendency from the cubic to tetragonal structure. The scanning electron microscopy micrographs reveal that the addition of Pb can affect microstructure. The dependent temperature dielectric permittivity and dielectric loss were investigated in the frequency range from 100 Hz to 1 MHz. The maximum peak of the dielectric permittivity versus temperature curve was broadened and a frequency dispersion of the dielectric permittivity was observed for the (Sr0.8Pb0.2)TiO3 ceramics. The results obtained at the frequency of 10 kHz reveal the Curie temperature linearly increased with the lead content. The fitted curves of temperature versus inverse dielectric permittivity at 10 kHz for ( Sr 1-x Pb x) TiO3 ceramics are consistent with Curie–Weiss law. The Pyroelectric properties were also investigated. The high pyroelectric coefficients and figure of merits indicate that the SPT ceramics are potential materials for pyroelectric sensors.

scholarly journals Microstructure and Mechanical Properties of 4Al Alumina-Forming Austenitic Steel after Cold-Rolling Deformation and Annealing

Materials ◽  
2020 ◽  
Vol 13 (12) ◽  
pp. 2767 ◽  
Author(s):  
Chenchen Jiang ◽  
Qiuzhi Gao ◽  
Hailian Zhang ◽  
Ziyun Liu ◽  
Huijun Li
Keyword(s):  
Grain Size ◽  
Cold Rolling ◽  
Grain Boundaries ◽  
Austenitic Steel ◽  
Rolling Reduction ◽  
X Ray Diffraction ◽  
Transmission Electron ◽  
Cold Rolling Reduction ◽  
Average Grain Size ◽  
Cold Rolled

Microstructural evolutions of the 4Al alumina-forming austenitic steel after cold rolling with different reductions from 5% to 30% and then annealing were investigated using electron backscattering diffraction (EBSD), X-ray diffraction (XRD) and transmission electron microscopy (TEM). Tensile properties and hardness were also measured. The results show that the average grain size gradually decreases with an increase in the cold-rolling reduction. The low angle grain boundaries (LAGBs) are dominant in the cold-rolled samples, but high angle grain boundaries (HAGBs) form in the annealed samples, indicating that the grains are refined under the action of dislocations. During cold rolling, high-density dislocations are initially introduced in the samples, which contributes to a large number of dislocations remaining after annealing. With the sustaining increase in cold-rolled deformation, the samples exhibit more excellent tensile strength and hardness due to the decrease in grain size and increase in dislocation density, especially for the samples subjected to 30% cold-rolling reduction. The contribution of dislocations on yield strength is more than 60%.

The Electrical Properties of BCZT Lead-Free Ceramics Induced by BaZrO3 Seeds

2016 ◽  
Vol 690 ◽  
pp. 114-119
Author(s):  
Piewpan Parjansri ◽  
Manlika Kamnoy ◽  
Uraiwan Intatha ◽  
Sukum Eitssayeam ◽  
Tawee Tunkasiri
Keyword(s):  
Grain Size ◽  
Electrical Properties ◽  
Perovskite Phase ◽  
Nano Particle ◽  
Sintered Ceramic ◽  
Voltage Coefficient ◽  
Lead Free Ceramics ◽  
Seed Content ◽  
Pure Perovskite Phase ◽  
Average Grain Size

Ba0.85Ca0.15Zr0.1Ti0.9O3 (BCZT) ceramics were produced by using the seed-induced method. The nano-particle BZ (BaZrO3) seeds were mixed with BaCO3, CaCO3, ZrO2 and TiO2 powder for preparing by the mixed oxide method. The XRD results indicated that all powder and sintered ceramic samples showed a pure perovskite phase with coexistence between rhombohedral and tetragonal phase. As the BZ seed content increased, the density of ceramics tended to decrease from 5.61 g/cm3 to 5.37 g/cm3. The average grain size of the ceramics was in the range of 12.15 -13.50 mm. The dielectric loss (tand) was less than 0.03 for all samples at room temperature (at 1 kHz). Other electrical properties, including dielectric constant (εr), remnant polarization (Pr), and piezoelectric charge coefficient (d33) values decreased with increasing BZ seed doping with relates to the decreasing grain size and density of BCZT ceramics. However, the values of coercive field (Ec) decreased and piezoelectric voltage coefficient (g33) increased with BZ seed doping.

scholarly journals The influence of Bi content on dielectric properties of Bi4–xTi3O12–1.5x ceramics

2017 ◽  
Vol 07 (03) ◽  
pp. 1750021 ◽  
Author(s):  
Hui Gong ◽  
Xiying Ke ◽  
Shuqin Yang ◽  
Zhaozhi Li ◽  
Huyin Su ◽  
...  
Keyword(s):  
Dielectric Constant ◽  
Grain Size ◽  
Curie Temperature ◽  
Dielectric Materials ◽  
Layered Perovskite ◽  
Low Loss ◽  
Solid State Method ◽  
Spectra Analysis ◽  
Perovskite Type ◽  
Perovskite Type Structure

A kind of lead-free dielectric materials, such as the bismuth layered perovskite-type structure of Bi[Formula: see text]Ti3O[Formula: see text], was prepared by the conventional solid-state method at 800[Formula: see text]C and sintered at 1100[Formula: see text]C. The variation of structure and electrical properties with different Bi concentration was studied. All the Bi[Formula: see text]Ti3O[Formula: see text] samples exhibited a single structured phase. SEM could be a better approach to present the microstructure of Bi[Formula: see text]Ti3O[Formula: see text] ceramics. It could be found that the grain size of Bi[Formula: see text]Ti3O[Formula: see text] sintered at 1100[Formula: see text]C was smaller than that of others among the five samples through grain size mechanics. Through impedance spectra analysis, we knew, when the Bi content was fixed, that the dielectric constant and the loss values increased with the decrease of frequency. The Curie temperature of the five samples was about 670[Formula: see text]C. In particular, while at the frequency of 100[Formula: see text]kHz, the lowest loss was 0.001 when Bi content was 3.98. The Bi[Formula: see text]Ti3O[Formula: see text] ceramics with the minimum grain size had highest dielectric constant and the relatively low loss. Due to its high Curie temperature, high permittivity and low loss, the Bi4Ti3O[Formula: see text] (BIT) ceramics have a broad application prospect in high density memory, generator, sensor, ferroelectric tunnel junctions and so on.

Impedance spectroscopy of grain boundaries in nanophase ZnO

1995 ◽  
Vol 10 (9) ◽  
pp. 2295-2300 ◽  
Author(s):  
J. Lee ◽  
J.-H. Hwang ◽  
J.J. Mashek ◽  
T.O. Mason ◽  
A.E. Miller ◽  
...  
Keyword(s):  
Activation Energy ◽  
Grain Size ◽  
Electrical Properties ◽  
Oxygen Partial Pressure ◽  
Partial Pressure ◽  
Grain Boundaries ◽  
Defect Characterization ◽  
Impedance Spectra ◽  
Gas Condensation ◽  
Average Grain Size

Sintered compacts of nanophase ZnO (∼60 nm average grain size, presintered at 600 °C) were made from powders (∼13 nm) prepared by the gas-condensation technique. Impedance spectra were taken as a function of temperature over the range 450–600 °C and as a function of oxygen partial pressure over the range 10−3−1 atm (550 and 600 °C only). The activation energy was determined to be 55 kJ/mole (0.57 eV) and was independent of oxygen partial pressure. The oxygen partial pressure exponent was −1/6. Impedance spectra exhibited nonlinear I-V behavior, with a threshold of approximately 6 V. These results indicate that grain boundaries are governing the electrical properties of the compact. Ramifications for oxygen sensing and for grain boundary defect characterization are discussed.

Fatigue Characteristic of Aluminum Alloy Plates with Different Thickness

2013 ◽  
Vol 477-478 ◽  
pp. 1284-1287 ◽  
Author(s):  
Hai Gen Jian ◽  
Min Xian Du ◽  
Feng Jiang ◽  
Zhi Min Yin
Keyword(s):  
Grain Size ◽  
Aluminum Alloy ◽  
Grain Boundaries ◽  
Fatigue Behavior ◽  
Propagation Direction ◽  
Fatigue Characteristic ◽  
Transmission Electron ◽  
Resistance Performance ◽  
Different Thickness ◽  
Better Than

The fatigue characteristic of 2124 aluminum alloy in T851 condition was investigated by means of scanning electron microscopy (SEM) and transmission electron microscope (TEM). And the result shows that, the fatigue life is closely related to the thickness of plates, this is because that different thickness of plates results in the variation of grain size, grain boundaries and substructures of alloy, which thus influence the fatigue behavior of 2124-T851 alloy. The number of grain boundaries along the propagation direction of cracks and the amount of substructures after heat treatment increase with the decline of thicknesses of 2124 alloy plates, while the grain size is reverse. However, no obvious size and dispersion changes for the precipitates. Comparatively, the fatigue resistance performance of 30mm thickness plate is better than the 40mm and 55mm thickness plates, which is due to the more profitable grain size, grain boundary and substructure.

Influence of CaO–SiO2 ratio on the chemistry of intergranular films in liquid-phase sintered alumina and implications for rate of erosive wear

2001 ◽  
Vol 16 (3) ◽  
pp. 652-665 ◽  
Author(s):  
Rik Brydson ◽  
Peter C. Twigg ◽  
Fiona Loughran ◽  
Frank L. Riley
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Grain Size ◽  
High Resolution ◽  
Grain Boundaries ◽  
Strong Dependence ◽  
Erosive Wear ◽  
Wear Rates ◽  
Aspect Ratios ◽  
Transmission Electron

Polycrystalline aluminas sintered with 10 wt% additions of calcium oxide (CaO) and silica (SiO2) in varying molar ratios were fabricated via precipitation, calcination, and hot pressing. Alumina microstructures were analyzed by scanning electron microscopy in terms of their mean grain size, grain size distribution, and grain aspect ratios. High-resolution transmission electron microscopy (HRTEM) showed the presence of an amorphous intergranular glassy phase at two- and three-grain boundaries. The intergranular film width at two-grain boundaries, determined by HRTEM, appeared to vary with the [CaO]:[SiO2] ratio of the additive as did the chemical composition and local chemistry, determined by high-resolution analytical transmission electron microscopy and scanning transmission electron microscopy (using both energy dispersive x-ray and electron energy loss spectroscopy). The factors influencing the erosive wear rate are discussed including the chemistry and associated fracture energy of the intergranular glassy film. Wet erosive wear rates of the densified materials were determined and had a strong dependence on the [CaO]:[SiO2] ratio in the additive.

Microstructure and Electrical Property Correlations in Ga:ZnO Transparent Conducting Thin Films

2006 ◽  
Vol 957 ◽  
Author(s):  
Vikram Bhosle ◽  
Jagdish Narayan
Keyword(s):  
Electrical Properties ◽  
Grain Boundaries ◽  
Zno Films ◽  
Nanocrystalline Films ◽  
X Ray Diffraction ◽  
Glass Substrates ◽  
Transmission Electron ◽  
Texture Characteristics ◽  
Crystal Films ◽  
Amorphous Glass

ABSTRACTWe report the correlations between processing, microstructure and electrical properties of Ga doped ZnO films. Films with varying grain size were grown on amorphous glass by changing the substrate and pulsed laser deposition variables. The results corresponding to these films were compared with those from epitaxial single crystal films grown on (0001) sapphire. Microstructural characteristics were analyzed in detail by using X-ray diffraction and transmission electron microscopy. Electrical properties were evaluated by resistivity measurements in the temperature range of 15-300K and Hall measurements at room temperature. It was observed that the grain boundaries and orientation of grains (texture characteristics) affected the carrier concentration and the mobility considerably in nanocrystalline films deposited on glass substrates. This effect is envisaged to occur as a result of trapping of electrons and build up of a potential barrier across the grain boundaries. However, the resistivity in nanocrystalline films could be decreased significantly by carefully controlling the deposition conditions. For a film deposited on glass at 2000C and 1 mtorr of oxygen partial pressure, we attained a minimum resistivity value of 1.8 × 10-4Ω-cm. As a comparison, the epitaxial films on sapphire substrates showed a resistivity of 1.4 × 10-4 Ω-cm, deposited at 4000C and pressure of 2.4 × 10-2 torr. Role of grain boundaries and defects in controlling the carrier generation and transport is considered in detail and possible mechanisms limiting the electrical conductivity in films with different microstructures are identified.

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