Sintering and dielectric properties of (Ta2O5)1−x (TiO2) x polycrystalline ceramics

2007 ◽  
Vol 21 (1-4) ◽  
pp. 577-580 ◽  
Author(s):  
Yue Wang ◽  
Xue-wen Zhu ◽  
Yi-jian Jiang
Keyword(s):  
Dielectric Properties ◽  
Polycrystalline Ceramics

Microwave dielectric properties of MO–La2O3–TiO2 (M = Ca, Sr, Ba) ceramics

2002 ◽  
Vol 17 (12) ◽  
pp. 3084-3089 ◽  
Author(s):  
Isuhak Naseemabeevi Jawahar ◽  
Narayana Iyer Santha ◽  
Mailadil Thomas Sebastian ◽  
Pezholil Mohanan
Keyword(s):  
Dielectric Properties ◽  
Single Phase ◽  
Microwave Dielectric Properties ◽  
Quality Factors ◽  
X Ray Diffraction ◽  
Microwave Dielectric ◽  
Narrow Bandwidth ◽  
Polycrystalline Ceramics ◽  
State Ceramic ◽  
High Dielectric

Single-phase polycrystalline ceramics in the MO–La2O3–TiO2 (M = Ca, Sr, Ba) system, such as cation-deficient hexagonal perovskites CaLa4Ti4O15, SrLa4Ti4O15, BaLa4Ti4O15, and Ca2La4Ti5O18 and the orthorhombic phases CaLa4Ti5O17 and CaLa8Ti9O31, were prepared through the solid-state ceramic route. The phases and structure of the ceramics were analyzed through x-ray diffraction and scanning electron microscopy. The microwave dielectric properties of the ceramics were studied using a network analyzer. The investigated ceramics show high εr in the range 42 to 54, high quality factors with Q ×f in the range 16,222 to 50,215 GHz, and low Tf in the range –25 to +6 ppm / °C. These high dielectric constant materials with high Q × f up to 50,215 GHz are suitable for applications where narrow bandwidth and extremely low insertion loss is necessary, especially at frequencies around 1.9 GHz.

High-Temperature Dielectric Properties of Polycrystalline Ceramics

1988 ◽  
Vol 124 ◽  
Author(s):  
W. W. Ho
Keyword(s):  
High Temperature ◽  
Dielectric Properties ◽  
Volume Expansion ◽  
Room Temperature ◽  
Experimental Methods ◽  
Dielectric Constants ◽  
Amorphous Phases ◽  
Temperature Loss ◽  
Polycrystalline Ceramics ◽  
Impurity Doping

ABSTRACTExperimental methods for determining the high-temperature millimeter-wave dielectric properties of solids are described and the data obtained on a wide variety of polycrystalline ceramics are reviewed. In general, the observed increase in dielectric constants with temperature can be modeled with a macroscopic dielectric virial expansion and shown to be primarily caused by an increase in polarizability due to volume expansion. The room-temperature loss tangents in low-absorption ceramics are probably caused by impurity doping of the primary and secondary crystalline phases at grain junctions and along grain boundaries. The rapid increase in loss tangent at high temperatures commonly observed in polycrystalline ceramics is associated with softening of intergranular amorphous phases resulting in an increase in localized electrical conductivity.

Microstructures and Dielectric Properties of CaCu3Ti4O12 Polycrystalline Ceramics

2007 ◽  
Vol 124-126 ◽  
pp. 143-146 ◽  
Author(s):  
Duk Keun Yoo ◽  
Sang Im Yoo
Keyword(s):  
Dielectric Properties ◽  
Sintered Density ◽  
Dielectric Constants ◽  
Abrupt Increase ◽  
Factors Affecting ◽  
Polycrystalline Ceramics ◽  
State Ceramic ◽  
Ceramic Process ◽  
Ccto Sample ◽  
Very High

We report important factors affecting the dielectric properties of CaCu3Ti4O12 (CCTO) polycrystalline ceramics prepared by the conventional solid-state ceramic process. The relative dielectric constants (εr) up to several thousands (~ 3,000 at 1 kHz) were gradually increased with increasing the sintered density of samples in the case that no exaggerated grain growth occurred. An abrupt increase in εr values were, however, accompanied by the formation of abnormally grown large grains, and thus with increasing the population of abnormally grown grains, which could be achieved by a prolonged sintering at 1060°C, the εr values were remarkably increased from several thousands to ~105. Optimally processed CCTO sample exhibited a very high εr of ~ 90,000 at 1 kHz.

Invited paper: Dielectric properties of CaCu3Ti4O12 polycrystalline ceramics

2011 ◽  
Vol 7 (4) ◽  
pp. 287-297 ◽  
Author(s):  
Sung Yun Lee ◽  
Youn Woo Hong ◽  
Sang Im Yoo
Keyword(s):  
Dielectric Properties ◽  
Polycrystalline Ceramics

Nanoscale Imaging of CaCu3Ti4O12 Dielectric Properties: The Role of Surface Defects

2007 ◽  
Vol 131-133 ◽  
pp. 443-448 ◽  
Author(s):  
Vito Raineri ◽  
Patrick Fiorenza ◽  
Raffaella Lo Nigro ◽  
Derek C. Sinclair
Keyword(s):  
Dielectric Properties ◽  
Scanning Probe Microscopy ◽  
Surface Defects ◽  
Polycrystalline Materials ◽  
Surface Imperfections ◽  
Polycrystalline Ceramics ◽  
Local Sample ◽  
Nanoscale Imaging ◽  
Sample Structure

Scanning probe microscopy with conductive tips has been used to image the dielectric properties of ceramics with giant permittivity. In particular, measurements in impedance mode and of local resistivity allowed to image the permittivity map on polycrystalline materials. Such imaging allows to correlate the dielectric properties with the local sample structure and with defects inside the single grains of the polycrystalline ceramics. However, artifacts due to surface imperfections should be distinguished from bulk properties and eliminated.

scholarly journals Sinterability and Dielectric Properties of LiTaO3-Based Ceramics with Addition of CoO

Materials ◽  
2020 ◽  
Vol 13 (7) ◽  
pp. 1506
Author(s):  
Youfeng Zhang ◽  
Yali Yao ◽  
Shasha He
Keyword(s):  
Dielectric Constant ◽  
Dielectric Properties ◽  
Dielectric Loss ◽  
Relative Density ◽  
Pressureless Sintering ◽  
Ferroelectric Crystal ◽  
Sintering Aid ◽  
Optimal Value ◽  
Polycrystalline Ceramics

Lithium tantalite (LiTaO3) is a common piezoelectric and ferroelectric crystal, but the LiTaO3 polycrystalline ceramics have rarely been reported, and their refractory character presents difficulties in their fabrication. In this study, LiTaO3-based ceramics with different amounts of CoO were prepared by pressureless sintering at 1250 °C, and the effects of the amount of sintering aid on the sinterability, microstructure, and dielectric properties of the ceramics were investigated. The relative densities of the LiTaO3-based ceramics were significantly improved by the addition of CoO powder. The LiTaO3-based ceramics achieved the highest relative density (89.4%) and obtained a well-grained microstructure when the added amount of CoO was 5 wt.%. Only the LiTaO3 phase in the ceramics was observed, indicating that the ions Co diffused into the LiTaO3 lattices and mainly existed in two forms: Co2+ and Co3+. The effects of the added amount of CoO on the dielectric properties of the LiTaO3-based ceramics were studied thoroughly. Consequently, the dielectric constant was enhanced, and the dielectric loss decreased in the LiTaO3-based ceramics with the addition of CoO. The optimal value was obtained at 5 wt.% of CoO-added LiTaO3-based ceramics.

Improved dielectric properties of BaTiO3-added CaCu3Ti4O12 polycrystalline ceramics

2013 ◽  
Vol 9 (3) ◽  
pp. 325-330 ◽  
Author(s):  
Hui Eun Kim ◽  
Soon-Mi Choi ◽  
Sung-Yun Lee ◽  
Youn-Woo Hong ◽  
Sang-Im Yoo
Keyword(s):  
Dielectric Properties ◽  
Polycrystalline Ceramics
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