Structural and dielectric properties of Bi2NbxVi−xO5.5 ceramics

1996 ◽  
Vol 11 (9) ◽  
pp. 2288-2292 ◽  
Author(s):  
K. B. R. Varma ◽  
K. V. R. Prasad
Keyword(s):  
Differential Scanning Calorimetry ◽  
Grain Size ◽  
Dielectric Properties ◽  
Curie Temperature ◽  
Room Temperature ◽  
Dielectric Constants ◽  
Scanning Calorimetry ◽  
Electron Microscopic ◽  
Scanning Electron Microscopic ◽  
Scanning Electron

Bi2Nbx V1−xO5.5 ceramics with x ranging from 0.01 to 0.5 have been prepared. The crystal system transforms from an orthorhombic to tetragonal at x 3= 0.1 and it persists until x = 0.5. Scanning electron microscopic (SEM) investigations carried out on thermally etched Bi2NbxV1−xO5.5 ceramics confirm that the grain size decreases markedly (18 μm to 4 μm) with increasing x. The shift in the Curie temperature (725 K) toward lower temperatures, with increasing x, is established by Differential Scanning Calorimetry (DSC). The dielectric constants as well as the loss tangent (tan δ) decrease with increasing x at room temperature.

scholarly journals Enhanced dielectric properties in la modified barium titanate ceramics

2019 ◽  
Vol 32 (2) ◽  
pp. 179-193 ◽  
Author(s):  
Vesna Paunovic ◽  
Zoran Prijic ◽  
Milos Djordjevic ◽  
Vojislav Mitic
Keyword(s):  
Grain Size ◽  
Phase Transformation ◽  
Dielectric Properties ◽  
Curie Temperature ◽  
Room Temperature ◽  
Dissipation Factor ◽  
Dielectric Constants ◽  
Phase Transformation Temperature ◽  
Average Grain Size ◽  
La Doped

Donor/acceptor (La/Mn) doped BaTiO3 ceramics, sintered at different temperatures, were studied regarding their microstructure and dielectric properties as well as the dielectric response in a ferroelectric/paraelectric regime. The concentrations of La3+ as donor, ranging from 0.1 to 5.0 at% were used for doping, while a content of Mn4+ as acceptor was at 0.05 at% in all samples. The sintering temperature of codoped samples were 1290? and 1350?C. A reduction in grain size and fine-grained microstructure with average grain size from 0.5 to 2.0 mm was observed in low doped samples, whereas the abnormal growth of individual grains took place in the 2 at% and 5 at% La doped specimens. The dielectric properties of these samples were investigated as a function of frequency (100Hz - 20 kHz) and temperature (20-180?C). The measured results suggested that both the dielectric constants of the ceramics (er at room temperature and ermax at the Curie temperature) decreased as the concentration of La3+ increased. The dielectric permittivity was in the range of 944 to 3200. For samples doped with 0.1 at% La and sintered at 1350?C, the highest dielectric constant value at room temperature (er= 3200) and Curie temperature (er= 5000) were measured. For all measured samples the dissipation factor was less than 0.09. With an increase in La contents, dielectric measurements exhibited shift in the Curie temperature (Tc) towards the low temperature. Using the Curie-Weiss and the modified Curie-Weiss law, Curie's constant C was calculated as well as the parameterg, which describes the deviation from the linear dependence er of T above the phase transformation temperature. The calculated values for g ranged from 1.01 to 1.43. These values indicate a sharp phase transformation in lowdoped and diffuse phase transformation in highly La doped samples. The phase transition was reflected in the values of C that started to decrease with increasing dopant content.

Curing behaviors of cyanate ester/epoxy copolymers and their dielectric properties

2016 ◽  
Vol 29 (10) ◽  
pp. 1175-1184 ◽  
Author(s):  
Yangxue Lei ◽  
Mingzhen Xu ◽  
Mingli Jiang ◽  
Yumin Huang ◽  
Xiaobo Liu
Keyword(s):  
Differential Scanning Calorimetry ◽  
Thermal Decomposition ◽  
Fourier Transform ◽  
Dielectric Properties ◽  
Small Extent ◽  
Dielectric Constants ◽  
Cyanate Ester ◽  
Scanning Calorimetry ◽  
Peak Fitting ◽  
Curing Kinetic

The curing behavior and dielectric properties of cyanate ester/epoxy (EP) with a latent initiator imidazole was investigated as a function of blend composition. Differential scanning calorimetry (DSC) was used to investigate the dynamic cure behavior of the blends. Multiheating rate DSC, peak fitting, and iso-conversion method were applied to analyze the curing kinetic parameters. Two distinct peaks were fitted from the dynamic DSC curve and the activation energies of each reaction varied with the increase of curing degrees. Fourier transform infrared spectra revealed that several reactions coexisted during the curing processes of cyanate and EP, resulting in the coexistence of the polymers and copolymers in the final composites. The dielectric properties of the composites were studied and the phenomenon that the dielectric constants for all of the composites are independent of frequency was observed. The thermal decomposition characteristics of the blends were investigated using thermogravimetric analysis. By increasing the content of EP, the thermal properties of the cured blends were improved to a small extent, while the char yield markedly decreased.

Dielectric Properties of Sr-Doped BaZrO3 Ceramics

2017 ◽  
Vol 907 ◽  
pp. 21-24
Author(s):  
Merve Torman ◽  
Kerim Emre Öksüz ◽  
Şaduman Şen ◽  
Uğur Şen
Keyword(s):  
Electron Microscopy ◽  
Dielectric Properties ◽  
Academic Research ◽  
Barium Zirconate ◽  
Dielectric Studies ◽  
Electron Microscopic ◽  
Average Grain Size ◽  
Scanning Electron Microscopic ◽  
Microscopic Studies ◽  
Scanning Electron

Perovskite compounds have received keen interest from academic research due to their unique properties such as ferroelectric, pyroelectric, piezoelectric, and dielectric properties. Nano sized oxides of strontium doped barium zirconate of general formula Ba1-xSrxZrO3 (x= 0.2, 0.4, 0.6, 0.8) have been prepared by a solid-state procedure. The surface morphology, microstructure, and phase analysis, of the sintered ceramics were characterized by field emission scanning electron microscopy (FE-SEM). Scanning electron microscopic studies showed the formation of cubic and hexagonal nanoparticles with an average grain size of 1.6μm±0.47 and 0.82±0.35μm. Dielectric studies were carried out as a function of frequency to explore the electrical properties of Sr-doped BaZrO3.

scholarly journals Thermal and Microstructure Analysis of Cocofoam Made from Blended Coconut Fiber with Latex Compound

CORD ◽  
2013 ◽  
Vol 29 (1) ◽  
pp. 9
Author(s):  
I.D.K. Anom
Keyword(s):  
Thermal Analysis ◽  
Differential Scanning Calorimetry ◽  
Electron Microscope ◽  
Room Temperature ◽  
Weight Ratio ◽  
Sem Analysis ◽  
Microstructure Analysis ◽  
Coconut Fiber ◽  
Scanning Calorimetry ◽  
Scanning Electron

Thermal and microstructure analysis of cocofoam made from vulcanized coconut fiber and latex compound were conducted. The cocofoam was produced by blending coconut fiber and latex compound with weight ratio of 10/25 (CF5-1) and 20/55 (CF5-2) at room temperature. The cocofoam characters were then analyzed by Scanning Electron Microscope (SEM), Thermogravimetric Analysis (TGA) and Differential Scanning Calorimetry (DTA) instruments. The result showed that the increase of coconut fiber and latex compound ratio produced a higher density of cocofoam. The highest value density was 0.6920 g/cm3 with flexibility of 90% produced by the CF5-2 sample. The SEM analysis showed that both specimens surface of the CF5-1 and CF5-2 samples have different pores size and the latex compound is not distributed thoroughly in the cocofoam. The thermal analysis showed that the production of cocofoam was largely determined by latex compound that served as fiber binder matrix. Cocofoam started to degrade at the temperature of 90oC and was damaged when it was heated at the temperature of 115oC for 2.5 hours.

Scanning Electron Microscopic Study of the Cell Surface

1969 ◽  
Vol 27 ◽  
pp. 36-37 ◽  
Author(s):  
Toichiro Kuwabara
Keyword(s):  
Tissue Fluid ◽  
Biological Application ◽  
Biological Structure ◽  
Electron Microscopic ◽  
Surface Appearance ◽  
Minute Amount ◽  
Scanning Electron Microscopic Study ◽  
Scanning Electron Microscopic ◽  
True Structure ◽  
Scanning Electron

Although scanning electron microscopy has a great potential in biological application, there are certain limitations in visualization of the biological structure. Satisfactory techniques to demonstrate natural surfaces of the tissue and the cell have been reported by several investigators. However, it is commonly found that the surface cell membrane is covered with a minute amount of mucin, secretory substance or tissue fluid as physiological, pathological or artefactual condition. These substances give a false surface appearance, especially when the tissue is fixed with strong fixatives. It seems important to remove these coating substances from the surface of the cell for demonstration of the true structure.

A scanning electron microscopic study on dissolving process of cholesterol gallstones by chenodeoxycholic acid (CDCA)

1978 ◽  
Vol 36 (2) ◽  
pp. 522-523
Author(s):  
T. Kanetaka ◽  
M. Cho ◽  
S. Kawamura ◽  
T. Sado ◽  
K. Hara
Keyword(s):  
Electron Microscope ◽  
Chenodeoxycholic Acid ◽  
Outer Surface ◽  
Electron Microscopic ◽  
Cholesterol Gallstones ◽  
The Core ◽  
Scanning Electron Microscopic Study ◽  
Scanning Electron Microscopic ◽  
Acceleration Voltage ◽  
Scanning Electron

The authors have investigated the dissolution process of human cholesterol gallstones using a scanning electron microscope(SEM). This study was carried out by comparing control gallstones incubated in beagle bile with gallstones obtained from patients who were treated with chenodeoxycholic acid(CDCA).The cholesterol gallstones for this study were obtained from 14 patients. Three control patients were treated without CDCA and eleven patients were treated with CDCA 300-600 mg/day for periods ranging from four to twenty five months. It was confirmed through chemical analysis that these gallstones contained more than 80% cholesterol in both the outer surface and the core.The specimen were obtained from the outer surface and the core of the gallstones. Each specimen was attached to alminum sheet and coated with carbon to 100Å thickness. The SEM observation was made by Hitachi S-550 with 20 kV acceleration voltage and with 60-20, 000X magnification.

A Comparative Study of Fractographic Replicas

1974 ◽  
Vol 32 ◽  
pp. 566-567
Author(s):  
Loren Anderson ◽  
Pat Pizzo ◽  
Glen Haydon
Keyword(s):  
Electron Microscopy ◽  
Electron Microscopic Examination ◽  
Direct Examination ◽  
Electron Microscopic ◽  
Reliable Technique ◽  
Service Failures ◽  
Transmission Electron ◽  
Mode Of Failure ◽  
Scanning Electron Microscopic ◽  
Scanning Electron

Transmission electron microscopy of replicas has long been used to study the fracture surfaces of components which fail in service. Recently, the scanning electron microscope (SEM) has gained popularity because it allows direct examination of the fracture surface. However, the somewhat lower resolution of the SEM coupled with a restriction on the sample size has served to limit the use of this instrument in investigating in-service failures. It is the intent of this paper to show that scanning electron microscopic examination of conventional negative replicas can be a convenient and reliable technique for determining mode of failure.

A Scanning Electron Microscopic Study of the Uriniferous Tubules

1973 ◽  
Vol 31 ◽  
pp. 622-623
Author(s):  
Peter M. Andrews
Keyword(s):  
Electron Microscopy ◽  
Scanning Electron Microscopy ◽  
Renal Glomerulus ◽  
Electron Microscopic ◽  
Vascular Perfusion ◽  
Scanning Electron Microscopic Study ◽  
Scanning Electron Microscopic ◽  
Collecting Tubules ◽  
Bowman's Capsule ◽  
Scanning Electron

Although there have been a number of recent scanning electron microscopic reports on the renal glomerulus, the advantages of scanning electron microscopy have not yet been applied to a systematic study of the uriniferous tubules. In the present investigation, scanning electron microscopy was used to study the ultrastructural morphology of the proximal, distal, thin loop, and collecting tubules. Material for observation was taken from rat kidneys which were fixed by vascular perfusion, sectioned by either cutting or fracturing technigues, and critically point dried.The brush border characterising proximal tubules is first detected on the luminal surface of Bowman's capsule adjacent to the urinary pole orifice. In this region one frequently finds irregular microvilli characterized by broad and flattened bases with occasional bulbous structures protruding from their surfaces.

Human Stapes Crura: Normal Ultrastructure. Scanning Electron Microscopic Findings

1975 ◽  
Vol 33 ◽  
pp. 528-529
Author(s):  
M.D. Graham
Keyword(s):  
Electron Microscope ◽  
Surgical Treatment ◽  
Scanning Electron Microscope ◽  
Osmic Acid ◽  
Human Cadaver ◽  
Electron Microscopic ◽  
Scanning Electron Microscopic ◽  
Normal Human ◽  
Microscopic Findings ◽  
Scanning Electron

The recent development of the scanning electron microscope has added great impetus to the study of ultrastructural details of normal human ossicles. A thorough description of the ultrastructure of the human ossicles is required in order to determine changes associated with disease processes following medical or surgical treatment.Human stapes crura were obtained at the time of surgery for clinical otosclerosis and from human cadaver material. The specimens to be examined by the scanning electron microscope were fixed immediately in the operating room in a cold phosphate buffered 2% gluteraldehyde solution, washed with Ringers, post fixed in cold 1% osmic acid and dehydrated in graded alcohol. Specimens were transferred from alcohol to a series of increasing concentrations of ethyl alcohol and amyl acetate. The tissue was then critical point dried, secured to aluminum stubs and coated with gold, approximately 150A thick on a rotating stage in a vacuum evaporator. The specimens were then studied with the Kent-Cambridge S4-10 Scanning Electron Microscope at an accelerating voltage of 20KV.

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