Conduction and Microwave Loss Mechanisms in Ba0.25Sr0.75TiO3 Films

2003 ◽  
Vol 784 ◽  
Author(s):  
Andrei Vorobiev ◽  
Par Rundqvist ◽  
Khaled Khamchane ◽  
Spartak Gevorgian
Keyword(s):  
Loss Tangent ◽  
Thermal Excitation ◽  
Low Loss ◽  
Loss Mechanism ◽  
Microwave Frequencies ◽  
Microwave Loss ◽  
Bst Thin Film ◽  
Dc Current ◽  
Charged Defects ◽  
Loss Mechanisms

ABSTRACTSilicon integrated parallel-plate Ba0.25Sr0.75TiO3 (BST) thin film varactors with Au bottom electrode have been prepared and characterized at dc and microwave frequencies. In the frequency range 0.045–45 GHz the varactors reveal extremely low loss tangent values (less than 0.025). However, this is still several times higher than loss in single crystal indicating occurrence of the extrinsic loss mechanisms. The analysis of BST film loss tangent and permittivity, depending on frequency and applied dc field, allow to attribute the dielectric loss to the charged defects. The dc current through varactor is found to be controlled by Poole-Frenkel mechanism associated with field enhanced thermal excitation of charge carriers from internal traps. It is assumed that charged defects and internal traps are the same type of BST film microstructure imperfection and possibly ascribed to be oxygen vacancies. The knowledge of the extrinsic loss mechanism and corresponding microstructure defects allows to optimize the deposition and/or anneal process and further improve the varactor performance.

A LTCC Material with Low Temperature Coefficient of Resonance Frequency

2006 ◽  
Vol 301 ◽  
pp. 105-108 ◽  
Author(s):  
Masaru Iwao ◽  
Yoshio Umayahara ◽  
Kazuyoshi Shindo
Keyword(s):  
Resonance Frequency ◽  
Temperature Coefficient ◽  
Loss Tangent ◽  
High Frequency ◽  
Low Loss ◽  
Fixed Amount ◽  
Passive Components ◽  
Microwave Loss ◽  
Crystal Phases ◽  
Layered Ceramic

For high frequency packaging applications, LTCC materials are required to have a low loss tangent to reduce the total microwave loss. For multi-layered ceramic devices with embedded passive components, besides a loss tangent, a small temperature coefficient of resonance frequency (TCF) is an important factor. To meet these demands, we developed a new LTCC material with a smaller TCF, less than +/-3ppm/oC, and a low loss tangent, 0.0012 at 15GHz. We designed the glass composition to precipitate two low-loss crystal phases during firing at 900 oC. One phase has a plus TCF and the other phase has a minus TCF. We also controlled the amount of the two crystal phases, so these crystal phases and the fixed amount of alumina filler make the sum of TCF for the LTCC material close to zero.

scholarly journals The Primary Origin of Excellent Dielectric Properties of (Co, Nb) Co-Doped TiO2 Ceramics: Electron-Pinned Defect Dipoles vs. Internal Barrier Layer Capacitor Effect

Molecules ◽  
2021 ◽  
Vol 26 (11) ◽  
pp. 3230
Author(s):  
Theeranuch Nachaithong ◽  
Narong Chanlek ◽  
Pairot Moontragoon ◽  
Prasit Thongbai
Keyword(s):  
Dielectric Properties ◽  
Loss Tangent ◽  
Barrier Layer ◽  
Dielectric Response ◽  
High Resistivity ◽  
Low Loss ◽  
Rutile Tio2 ◽  
Complex Defect ◽  
Very High ◽  
Co Doped

(Co, Nb) co-doped rutile TiO2 (CoNTO) nanoparticles with low dopant concentrations were prepared using a wet chemistry method. A pure rutile TiO2 phase with a dense microstructure and homogeneous dispersion of the dopants was obtained. By co-doping rutile TiO2 with 0.5 at.% (Co, Nb), a very high dielectric permittivity of ε′ » 36,105 and a low loss tangent of tanδ » 0.04 were achieved. The sample–electrode contact and resistive outer-surface layer (surface barrier layer capacitor) have a significant impact on the dielectric response in the CoNTO ceramics. The density functional theory calculation shows that the 2Co atoms are located near the oxygen vacancy, creating a triangle-shaped 2CoVoTi complex defect. On the other hand, the substitution of TiO2 with Nb atoms can form a diamond-shaped 2Nb2Ti complex defect. These two types of complex defects are far away from each other. Therefore, the electron-pinned defect dipoles cannot be considered the primary origins of the dielectric response in the CoNTO ceramics. Impedance spectroscopy shows that the CoNTO ceramics are electrically heterogeneous, comprised of insulating and semiconducting regions. Thus, the dielectric properties of the CoNTO ceramics are attributed to the interfacial polarization at the internal insulating layers with very high resistivity, giving rise to a low loss tangent.

Giant dielectric permittivity with low loss tangent and excellent non−Ohmic properties of the (Na+, Sr2+, Y3+)Cu3Ti4O12 ceramic system

2020 ◽  
Vol 46 (7) ◽  
pp. 9780-9785 ◽  
Author(s):  
Pariwat Saengvong ◽  
Jakkree Boonlakhorn ◽  
Narong Chanlek ◽  
Bundit Putasaeng ◽  
Prasit Thongbai
Keyword(s):  
Dielectric Permittivity ◽  
Loss Tangent ◽  
Ceramic System ◽  
Low Loss ◽  
Giant Dielectric
Sign in / Sign up

Export Citation Format

Share Document