scholarly journals Development and Characterization of Titanium Dioxide Ceramic Substrates with High Dielectric Permittivities

Materials ◽  
2020 ◽  
Vol 13 (2) ◽  
pp. 386 ◽  
Author(s):  
Antonio E. Freitas ◽  
Taise M. Manhabosco ◽  
Ronaldo J. C. Batista ◽  
Alan K. Rêgo Segundo ◽  
Humberto X. Araújo ◽  
...  
Keyword(s):  
Grain Size ◽  
Titanium Dioxide ◽  
Rutile Phase ◽  
Solid State Reactions ◽  
Relative Dielectric Permittivity ◽  
Dielectric Parameters ◽  
Ceramic Substrates ◽  
Average Grain Size ◽  
High Dielectric ◽  
Increasing Temperature

Titanium dioxide substrates have been synthesized by means of solid-state reactions with sintering temperatures varying from 1150 °C up to 1350 °C. X-ray diffraction and scanning electron microscopy (SEM) where employed to investigate the crystal structure, grain size and porosity of the resulting samples. The obtained ceramics are tetragonal (rutile phase) with average grain sizes varying from 2.94 µm up to 5.81 µm. The average grain size of samples increases with increasing temperature, while the porosity decreases. The effect of microstructure on the dielectric properties has been also studied. The reduction of porosity of samples significantly improves the dielectric parameters (relative dielectric permittivity and loss tangent) in comparison to those of commercial substrates, indicating that the obtained ceramic substrates could be useful in the miniaturization of telecommunication devices.

Autothermal Gelation Synthesis of Uniform Titania Nanoparticles

2010 ◽  
Vol 148-149 ◽  
pp. 1188-1191
Author(s):  
Xi Xin Wang ◽  
Jian Ling Zhao ◽  
Zhao Hui Meng ◽  
Jia Wei Yan
Keyword(s):  
Grain Size ◽  
Tio2 Nanoparticles ◽  
Anatase Phase ◽  
Xrd Analysis ◽  
Rutile Phase ◽  
Titania Nanoparticles ◽  
Gelation Process ◽  
Average Grain Size ◽  
Process Effects ◽  
20 Nm

Titania nanoparticles were successfully synthesized through an easily controlled and simple autothermal gelation process. Effects of H2O2 concentrations, solvent quantity and dissolving temperature were investigated in detail. DSC–TGA and XRD analysis showed that the synthesized TiO2 nanoparticles were in anatase phase at 400°C and in rutile phase at 650°C. TEM image indicated that the titania nanoparticles were uniform and approximately spherical, the average grain size of the product was about 20 nm.

TEMPERATURE-DEPENDENT MODIFICATIONS OF Ag/SiO2/p-Si SCHOTTKY CONTACTS FORMED AT 20 K

2010 ◽  
Vol 09 (03) ◽  
pp. 135-138
Author(s):  
A. ALI ◽  
M. YASAR ◽  
F. NASIM ◽  
A. S. BHATTI
Keyword(s):  
Grain Size ◽  
Barrier Height ◽  
Ideality Factor ◽  
Thermal Evaporation ◽  
Schottky Contacts ◽  
Temperature Dependent ◽  
Ideal Behavior ◽  
Annealing Temperatures ◽  
Average Grain Size ◽  
Increasing Temperature

The Schottky contacts of Ag/SiO2 /p- Si were fabricated by thermal evaporation at 20 K. The effect of annealing temperatures varying from 373 to 773 K on the morphology and electrical properties of these contacts was investigated. The average grain size increased while the density of grains decreased with increasing temperature. Ideality factor initially observed was as high as 4.15 with a low barrier height of 0.04 eV for contact grown at 20 K. Annealing resulted in shift of ideality factor and barrier height towards ideal behavior. Thus, it is demonstrated that Ag/SiO2 /p- Si contacts grown at low temperature can be modified by annealing.

scholarly journals The effect of secondary abnormal grain growth on the dielectric properties of La/Mn co-doped BaTiO3 ceramics

2006 ◽  
Vol 38 (3) ◽  
pp. 273-281 ◽  
Author(s):  
Lj.M. Zivkovic ◽  
V.V. Paunovic ◽  
N.Lj. Stamenkov ◽  
M.M. Miljkovic
Keyword(s):  
Grain Growth ◽  
Ferroelectric Phase ◽  
Eutectic Temperature ◽  
Ferroelectric Properties ◽  
Abnormal Grain Growth ◽  
Solid State Reactions ◽  
Dielectric Parameters ◽  
High Electrical Resistivity ◽  
Uniform Microstructure ◽  
Average Grain Size

La/Mn-codoped BaTiO3 systems, obtained by solid state reactions, were investigated regarding their microstructure characteristics and ferroelectric properties. Different concentrations of La2O3 were used for doping, ranging from 0.1 to 5.0 at% La, while a content of Mn was constant at 0.05 at%. For all samples sintered below the eutectic temperature (1332?C), a uniform microstructure was formed with average grain size from 1-3 ?m. The appearance of secondary abnormal grains with (111) double twins grains with curved or faceted grain boundaries were observed in La/Mn BaTiO3 ceramics after sintering at temperatures above the eutectic temperature. All sintered samples exhibited a high electrical resistivity. Better dielectric performances were obtained for low doped samples (0.1 at% La) sintered at 1350?C. For samples with La content above 1.0 at% a lower value in dielectric permittivity at higher sintering temperature is due to secondary abnormal grain growth, and to the presence of a non-ferroelectric phase rich in La. The Curie constant together with other dielectric parameters were also calculated.

scholarly journals SYNTHESIS AND INVESTIGATION OF BARIUM TITANATE STANNATE SOLID SOLUTION

2019 ◽  
Vol 85 (12) ◽  
pp. 75-83
Author(s):  
Oleg V’yunov ◽  
Leonid Kovalenko ◽  
Anatolii Belous
Keyword(s):  
Solid Solution ◽  
Grain Size ◽  
Barium Titanate ◽  
Solid Solutions ◽  
Sintering Temperature ◽  
Solid State Reactions ◽  
Glass Forming ◽  
Average Grain Size ◽  
Polycrystalline Ceramics ◽  
Tin Content

Solid  solutions  of barium  titanate-stannate,  Ba(Ti,Sn)O3  have been investigated.  The  sequence  of phase  transformations  during  the synthesis  by solid  state  reactions  technique  has  been  determined,  crystallographic  and  microscopic  examinations  of polycrystalline  ceramics  based  on Ba(Ti,Sn)O3  solid solutions  have been  carried  out.  The  laws  governing  the change  in crystallographic  parameters  and the average  grain  size  as a function  of tin  content  have  been  shown.  Electrophysical  investigations  of the  obtained ceramics  have been carried out.  It has  been  found that  the dielectric  pa-rameters  (e and tgd)  of Ba(Ti,Sn)O3-based  ceramics  can  be improved  and  their  sintering  temperature  can  be reduced  by the addition  of  0.5 wt.% manganese  oxide(IV)  and 2 wt. % of  low-melting  glass-forming  admixture  AST (Al2O3–SiO2–TiO2).  It  has been  shown  that  the  obtained  materials  have  promise  in creating  ceramic  capacitors  based  on  them.

Agglomeration Eliminating Antimony Doped Tin Oxide (ATO) Nanoparticles by Different Drying Methods

2011 ◽  
Vol 399-401 ◽  
pp. 543-547
Author(s):  
Zi Li Liu ◽  
Qian Wen Dai ◽  
Sheng Zhou Chen ◽  
Zhe Guo
Keyword(s):  
Grain Size ◽  
Tin Oxide ◽  
Azeotropic Distillation ◽  
Rutile Phase ◽  
Microwave Drying ◽  
Drying Methods ◽  
Infrared Drying ◽  
Average Grain Size ◽  
Bet Method ◽  
Colour Changes

Antimony doped tin oxide (ATO) nanoparticles were synthesized via complex-homogeneous coprecipitation. Then different drying methods (such as azeotropic distillation, infrared drying and microwave drying, etc.) were used to eliminate the agglomeration. The nanoparticles were characterized by thermal analysis, X-ray diffraction (XRD), and Brunauer-Emmett-Teller measurements (BET). The result shows that ATO nanopaticles with tetragonal rutile phase structure are all well crystallized after the drying processes above, and the average grain size is between 29.30 nm and 71.52 nm. The grain size estimated by BET method is similar to the result of Scherrer equation, and the nanoparticles prepared by azeotropic distillation have better crystallinity comparing to other methods. With the extension of the distillation time, the grain size increases, and the colour changes from grey blue to light grey. Moreover, the combination of azeotropic distillation and infrared drying can prepare smaller and better crystalline ATO nanoparticles.

STRUCTURAL TRANSFORMATION IN NANOPHASE TITANIUM DIOXIDE

1999 ◽  
Vol 13 (05) ◽  
pp. 167-174 ◽  
Author(s):  
MUYING WU ◽  
WEIFENG ZHANG ◽  
ZULIANG DU ◽  
YABIN HUANG
Keyword(s):  
Raman Spectroscopy ◽  
Grain Size ◽  
Phase Transformation ◽  
Titanium Dioxide ◽  
Structural Transformation ◽  
Annealing Temperature ◽  
Sol Gel ◽  
X Ray ◽  
Average Grain Size ◽  
Gel Technique

Nanophase TiO 2 was prepared by a stearic acid sol–gel technique. X-ray measurements showed that the as-prepared sample is anatase TiO 2 phase with an average grain size of 10.4 nm. Raman spectroscopy was used to investigate the structural transformation from anatase-to-rutile in the nanophase TiO 2 annealed at a series of temperatures from 450 to 650°C. The results showed that the transformation took place in a wide annealing temperature range. The related mechanism to the phase transformation is discussed according to nanometer size effect.

Effect of TiCl4 Concentration and Acidity on Size and Phase of TiO2 Nanopowders Prepared by Non-Hydrolytic Sol-Gel Method

2011 ◽  
Vol 412 ◽  
pp. 32-35
Author(s):  
Jian Sun ◽  
Yan Xiang Wang ◽  
Xiao Yan Li
Keyword(s):  
Grain Size ◽  
Sol Gel ◽  
Rutile Phase ◽  
Gel Method ◽  
Sol Gel Method ◽  
Reaction Solution ◽  
Average Grain Size ◽  
Method Effects

TiO2nanopowders were synthesized by non-hydrolytic sol−gel method. Effects of TiCl4concentration and acidity on the properties of TiO2nanopowders were investigated. The results showed that the average grain size of TiO2decreased with the increasing of TiCl4concentration. H+can inhibit the growth of TiO2particles and Cl-is conducive to the formation of rutile phase. When 2.06M HCl was used as the reaction solution, TiO2microspheres with diameter 2μm was obtained, and TiO2microspheres was composed of anatase and rutile phase.

Surface Modification and its Influence on the Microstructure and Creep Resistance of Nickel Based Superalloy René 77 / Modyfikacja Powierzchniowa Oraz Jej Wpływ Na Mikrostrukture I Wytrzymałosc Na Pełzanie Odlewów Z Nadstopu Niklu Ren´E 77

2013 ◽  
Vol 58 (1) ◽  
pp. 95-98 ◽  
Author(s):  
M. Zielinska ◽  
J. Sieniawski
Keyword(s):  
Mechanical Properties ◽  
Grain Size ◽  
Surface Modification ◽  
Turbine Blades ◽  
Processing Parameters ◽  
Grain Structure ◽  
Creep Tests ◽  
Cobalt Aluminate ◽  
Nickel Based Superalloy ◽  
Average Grain Size

Superalloy René 77 is very wide used for turbine blades, turbine disks of aircraft engines which work up to 1050°C. These elements are generally produced by the investment casting method. Turbine blades produced by conventional precision casting methods have coarse and inhomogeneous grain structure. Such a material often does not fulfil basic requirements, which concern mechanical properties for the stuff used in aeronautical engineering. The incorporation of controlled grain size improved mechanical properties. This control of grain size in the casting operation was accomplished by the control of processing parameters such as casting temperature, mould preheating temperature, and the use of grain nucleates in the face of the mould. For nickel and cobalt based superalloys, it was found that cobalt aluminate (CoAl2O4) has the best nucleating effect. The objective of this work was to determine the influence of the inoculant’s content (cobalt aluminate) in the surface layer of the ceramic mould on the microstructure and mechanical properties at high temperature of nickel based superalloy René 77. For this purpose, the ceramic moulds were made with different concentration of cobalt aluminate in the primary slurry was from 0 to 10% mass. in zirconium flour. Stepped and cylindrical samples were casted for microstructure and mechanical examinations. The average grain size of the matrix ( phase), was determined on the stepped samples. The influence of surface modification on the grain size of up to section thickness was considered. The microstructure investigations with the use of light microscopy and scanning electron microscopy (SEM) enable to examine the influence of the surface modification on the morphology of ’ phase and carbides precipitations. Verification of the influence of CoAl2O4 on the mechanical properties of castings were investigated on the basis of results obtained form creep tests.

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