Preparation and microwave characterization of BaNd2−xSmxTi4O12 (0≤x≤2) ceramics and their effect on the temperature coefficient of dielectric constant in polytetrafluoroethylene composites

This paper presents a novel approach for the characterization of microwave properties of carbon-based nanopowders, decorated or not with magnetic nanoparticles. Their microwave parameters, dielectric constant, electrical conductivity, and complex magnetic permeability are extracted from measurements performed using a single transmission line acting as a test cell. Two geometries of transmission line were tested, and successful results were obtained with each one of them. The measurement results are assessed by a phenomenological model enabling to fit the measurement of the dielectric constant and conductivity, providing an insight on the compacity quality of the powder sample. Also, the extraction of the permeability is validated by the detection of a ferromagnetic resonance showing a linear dependence on external DC magnetic field.

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Development of BaTiO3 Based X7R Wafers for Single-Layer Capacitors

Key Engineering Materials ◽

10.4028/www.scientific.net/kem.280-283.69 ◽

2007 ◽

Vol 280-283 ◽

pp. 69-72

Author(s):

Zhengbo Yu ◽

Vladimir D. Krstić ◽

Jack Ng

Keyword(s):

Mechanical Properties ◽

Dielectric Constant ◽

Temperature Coefficient ◽

High Frequency ◽

Sintering Temperature ◽

Single Layer ◽

Dissipation Factor ◽

Cold Isostatic Pressing ◽

Dry Pressing

Research on the development and characterization of X7R BaTiO3 dielectric wafers for high frequency single-layer capacitors has been carried out. Commercial BaTiO3 powders were processed and optimized in dielectric constant (er), dissipation factor (DF) and temperature coefficient of capacitance (TCC). The results indicate a strong effect of sintering temperature on dielectric properties as well as on mechanical properties of the BaTiO3. It has been shown that the highest dielectric constant is achieved at high sintering temperatures (>1400°C) and lowest TCC at lower sintering temperatures (<1300°C). By optimizing fabrication process e.g. dry pressing, cold isostatic pressing, sintering, and machining such as grinding and lapping, BaTiO3 wafers of dielectric constant from 3400 to 3600, with a diameter approximately 50mm and thickness 150µm, have been manufactured successfully. The fabricated thin wafers exhibit the X7R capacitor characteristics of the dissipation factor (<3%) and temperature coefficient of capacitance (<±15%) in the temperature range of –55°C to 125°C.

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A CPW linear resonator method for the microwave characterization of high dielectric constant films

Microwave and Optical Technology Letters ◽

10.1002/mop.22176 ◽

2007 ◽

Vol 49 (3) ◽

pp. 521-524 ◽

Cited By ~ 5

Author(s):

Luciene S. Demenicis ◽

Rodolfo A. A. Lima ◽

Luiz Fernando M. Conrado ◽

Walter Margulis ◽

Maria Cristina R. Carvalho

Keyword(s):

Dielectric Constant ◽

High Dielectric Constant ◽

Microwave Characterization ◽

Resonator Method ◽

High Dielectric

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Structural and dielectric characterization of Ba4Nd2Ti4+xTa6−xO30−x/2 nonstoichiometric ceramics

Journal of Materials Research ◽

10.1557/jmr.2001.0394 ◽

2001 ◽

Vol 16 (10) ◽

pp. 2859-2863 ◽

Cited By ~ 2

Author(s):

X. M. Chen ◽

X. H. Zheng ◽

J. Wang

Keyword(s):

Dielectric Constant ◽

Dielectric Loss ◽

Temperature Coefficient ◽

Partial Substitution ◽

Dielectric Characterization ◽

Low Dielectric ◽

Dielectric Ceramics ◽

Reduced Temperature

Ba4Nd2Ti4Ta6O30 dielectric ceramics with high-Ε and low dielectric loss were modified to improve the temperature coefficient of dielectric constant. Through partial substitution of Ti4+ for Ta5+, a significantly reduced temperature coefficient of dielectric constant (tΕ = –664p pm/°C) combined with a dielectric constant above 110 and a low dielectric loss (tanδ–0.0005 to 0.0006 at 1 MHz) resulted in the nonstoichiometric dielectric ceramics with nominal compositions Ba4Nd2Ti4+xTa6-xO30?x/2 (x = 0.8–1.2).

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