Enhancing Tunability and Decreasing Temperature Sensitivity

2003 ◽  
Vol 784 ◽  
Author(s):  
S. C. Tidrow ◽  
A. Tauber ◽  
D. M. Potrepka ◽  
F. Crowne ◽  
B. Rod
Keyword(s):  
Dielectric Constant ◽  
Low Temperature ◽  
Electric Field ◽  
Temperature Coefficient ◽  
Temperature Sensitivity ◽  
Room Temperature ◽  
Single Phase ◽  
Perovskite Oxide ◽  
Microwave Devices ◽  
The Military

ABSTRACTThe employment of judicious substitution on B-sites in the perovskite oxide, BaTiO3, has yielded materials suitable for relatively temperature insensitive electric field tunable microwave devices. The properties, single-phase cubic perovskites with tunabilities as large as 30% at 1 V/μm and room temperature that possess low temperature coefficient of dielectric constant and tunability over the majority of the military specified temperature range, -55 to 125 °C, have been achieved in the charge compensated system Ba1-xSrxTi1–2yCyDyO3 where C is Ho, Er, Tm, Lu, Sc, Y, In and D is Ta, Sb with 0 ≤ X ≤ 0.2, and 0 < y ≤ 0.10.

scholarly journals Structure and electric properties of cerium substituted SrBi1.8Ce0.2Nb2O9 and SrBi1.8Ce0.2Ta2O9 ceramics

2016 ◽  
Vol 10 (3) ◽  
pp. 183-188 ◽  
Author(s):  
Mohamed Afqir ◽  
Amina Tachafine ◽  
Didier Fasquelle ◽  
Mohamed Elaatmani ◽  
Jean-Claude Carru ◽  
...  
Keyword(s):  
Dielectric Constant ◽  
Solid State ◽  
Room Temperature ◽  
Single Phase ◽  
Solid State Reaction Method ◽  
X Ray Diffraction ◽  
Reaction Method ◽  
X Ray ◽  
Lcr Meter ◽  
Curie Temperature Tc

SrBi1.8Ce0.2Nb2O9 (SBCN) and SrBi1.8Ce0.2Ta2O9 (SBCT) powders were prepared via solid-state reaction method. X-ray diffraction analysis reveals that the SBCN and SBCT powders have the single phase orthorhom-bic Aurivillius structure at room temperature. The contribution of Raman scattering and FTIR spectroscopy of these samples were relatively smooth and resemble each other. The calcined powders were uniaxially pressed and sintered at 1250?C for 8 h to obtaine dense ceramics. Dielectric constant, loss tangent and AC conductivity of the sintered Ce-doped SrBi2Nb2O9 and SrBi2Ta2O9 ceramics were measured by LCR meter. The Ce-doped SBN (SBCN) ceramics have a higher Curie temperature (TC) and dielectric constant at TC (380?C and ?? ~3510) compared to the Ce-doped SBT (SBCT) ceramics (330?C and ?? ~115) when measured at 100Hz. However, the Ce-doped SBT (SBCT) ceramics have lower conductivity and dielectric loss.

Microwave dielectric properties of Ca[(Li1/3Nb2/3)1−xMx]O3−δ (M = Sn, Ti) ceramics

1999 ◽  
Vol 14 (9) ◽  
pp. 3567-3570 ◽  
Author(s):  
Ji-Won Choi ◽  
Chong-Yun Kang ◽  
Seok-Jin Yoon ◽  
Hyun-Jai Kim ◽  
Hyung-Jin Jung ◽  
...  
Keyword(s):  
Dielectric Constant ◽  
Dielectric Properties ◽  
Resonant Frequency ◽  
Temperature Coefficient ◽  
Quality Factor ◽  
Single Phase ◽  
Microwave Dielectric Properties ◽  
Multiphase Materials ◽  
Microwave Dielectric ◽  
Orthorhombic Perovskite

The microwave dielectric properties of Ca[(Li1/3Nb2/3)1−xMx]O3−δ (M = Sn, Ti, 0 ≤ x ≤ 0.5) ceramics were investigated. In general, the ceramics prepared were multiphase materials. However, single-phase specimens having orthorhombic perovskite structure similar to CaTiO3 could be obtained in the vicinity of Sn = 0.2 to 0.3, and Ti = 0.2. As Sn concentration increased, the dielectric constant (εr) decreased and the quality factor (Q) significantly increased within the limited Sn concentration. As Ti concentration increased, the dielectric constant (εr) increased, the quality factor (Q) decreased, and the temperature coefficient of resonant frequency (τf) changed from a negative to positive value. The temperature coefficient of resonant frequency of 0 ppm/°C was realized at Ti = 0.2. The Q · fo value and εr for this composition were found to be 26100 GHz and 38.6, respectively.

Electroluminescence from GalnN Quantum Wells Grown on Non-(0001) Facets of Selectively Grown GaN Stripes

2004 ◽  
Vol 831 ◽  
Author(s):  
Barbara Neubert ◽  
Frank Habel ◽  
Peter Bruckner ◽  
Ferdinand Scholz ◽  
Till Riemann ◽  
...  
Keyword(s):  
Low Temperature ◽  
Electric Field ◽  
Quantum Wells ◽  
Room Temperature ◽  
Light Emission ◽  
Low Pressure ◽  
Lower Efficiency ◽  
Strong Light ◽  
The Common ◽  
Piezo Electric

ABSTRACTNon (0001) GalnN QWs have been grown by low pressure MOVPE on side facets of triangular shaped selectively grown GaN stripes. By analysing low temperature photo- and cathodoluminescence and room temperature electroluminescence, we found strong indications, that both, In and Mg are less efficiently incorporated on these side facets compared to the common (0001) plane with even lower efficiency for stripes running along (1–100) compared to (11–20). Nevertheless, we observed strong light emission from these quantum wells, supposed to be at least partly caused by the reduced piezo-electric field.

scholarly journals Synthesis and characterization of lead-free ternary component BST–BCT–BZT ceramic capacitors

2014 ◽  
Vol 04 (02) ◽  
pp. 1450014 ◽  
Author(s):  
Venkata Sreenivas Puli ◽  
Dhiren K. Pradhan ◽  
Brian C. Riggs ◽  
Shiva Adireddy ◽  
Ram S. Katiyar ◽  
...  
Keyword(s):  
Phase Transition ◽  
Dielectric Constant ◽  
Energy Density ◽  
Electric Field ◽  
Hysteresis Loop ◽  
Electric Fields ◽  
Room Temperature ◽  
Thermal Hysteresis ◽  
Lead Free ◽  
Maximum Electric Field

Polycrystalline sample of lead-free 1/3( Ba 0.70 Sr 0.30 TiO 3) + 1/3( Ba 0.70 Ca 0.30 TiO 3) + 1/3( BaZr 0.20 Ti 0.80 O 3)( BST - BCT - BZT ) ceramic was synthesized by solid state reaction method. Phase purity and crystal structure of as-synthesized materials was confirmed by X-ray diffraction (XRD). Temperature-dependent dielectric permittivity studies demonstrated frequency-independent behavior, indicating that the studied sample has typical diffuse phase transition behavior with partial thermal hysteresis. A ferroelectric phase transition between cubic and tetragonal phase was noticed near room temperature (~ 330 K). Bulk P–E hysteresis loop showed a saturation polarization of 20.4 μC/cm2 and a coercive field of ~ 12.78 kV/cm at a maximum electric field of ~ 115 kV/cm. High dielectric constant (ε ~ 5773), low dielectric loss (tan δ ~ 0.03) were recorded at room temperature. Discharge energy density of 0.44 J/cm3 and charge energy density of 1.40 J/cm3 were calculated from nonlinear ferroelectric hysteresis loop at maximum electric field. Dielectric constant at variable temperatures and electric fields, ferroelectric to paraelectric phase transition and energy storage properties were thoroughly discussed.

Low Temperature Sintering Ba3Ti5Nb6O28 Ceramics with Tunable Temperature Coefficient of Dielectric Constant

2008 ◽  
Vol 368-372 ◽  
pp. 170-172 ◽  
Author(s):  
Dong Guo ◽  
Zhi Yuan Ling ◽  
Xing Hu
Keyword(s):  
Dielectric Constant ◽  
Dielectric Properties ◽  
Dielectric Loss ◽  
Low Temperature ◽  
Temperature Coefficient ◽  
Sintering Temperature ◽  
Low Temperature Sintering

A middle permittivity dielectrics with the tunable temperature coefficient of dielectric constant (τε) in the BaO-TiO2-Nb2O5 system, Ba3Ti5Nb6O28, has been synthesized and characterized. The dielectric properties of Ba3Ti5Nb6O28 measured at 1MHz are as follows: dielectric constant (εr) ~38, dielectric loss (tanδ)<0.0002, temperature coefficient of dielectric constant (τε)~-22ppm/°C. The Ba3Ti5Nb6O28 phase satisfies the requirements of NP0 (MLCC) dielectrics, but the sintering temperature of the Ba3Ti5Nb6O28 phase (1250~1300°C) is too high to be co-fired with Ag or Cu electrodes. To lower the sintering temperature, an appropriate amount of ZnO-B2O3 frit (5~7wt.%) was added to the Ba3Ti5Nb6O28 phase and dense ceramics were obtained at the sintering temperature lower than 1000°C. Furthermore, the CaNb2O6 phase with the positive τε of 65ppm/°C was incorporated into the Ba3Ti5Nb6O28 phase to adjust the temperature coefficient of dielectric constant from negative to positive(-22~30ppm/°C). Near zero τε ceramics with high εr (38) and low tanδ (0.0002) were obtained at the composition of Ba3Ti5Nb6O28/ CaNb2O6/ ZB frit=76:17:7 wt.%.

The Observations on Faulted Dipoles in Deformed Tial—Based Alloys

1994 ◽  
Vol 364 ◽  
Author(s):  
Y. Gao ◽  
J. Zhu ◽  
Q. G. Cai
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Plastic Deformation ◽  
Low Temperature ◽  
Deformation Temperature ◽  
Room Temperature ◽  
Single Phase ◽  
Deformation Structure ◽  
Partial Dislocations ◽  
Transmission Electron

AbstractThe deformation structure of polycrystalline TiAl-based alloys after uniaxial compression at temperature range from 77K to 1073K has been examined using transmission electron microscopy. It was observed that a large number of faulted dipoles are commonly present in deformation structure of the alloys compressed at low temperature 77K and room temperature. The nature of the faulted dipoles has been determined to be intrinsic stacking fault lying on {111} plane, bounded by 1/6<112] partial dislocations. A possible mechanism for the formation of the faulted dipoles was suggested. The results of the statistic observation shows that faulted dipoles in deformed Ti-48A1 and Ti-(47–48) Al-X (X = V,Cr,Mn) alloys are less than those in single phase Ti-52A1 alloy, and the number of the faulted dipoles decreases with increasing deformation temperature. The effect of the faulted dipoles on plastic deformation of the alloy was discussed.

Phase Formation and Grain Growth of BSCZT Ceramics Prepared by BST-BZT Seed Induced Method

2018 ◽  
Vol 766 ◽  
pp. 175-179
Author(s):  
Jiraporn Dangsak ◽  
Sukum Eitssayeam ◽  
Denis Russell Sweatman ◽  
Uraiwan Intatha
Keyword(s):  
Dielectric Constant ◽  
Grain Size ◽  
Phase Formation ◽  
Room Temperature ◽  
Single Phase ◽  
Seed Crystal ◽  
Lead Free ◽  
X Ray Diffraction ◽  
X Ray ◽  
Density Values

In this work, lead-free Ba0.4Sr0.4Ca0.2Zr0.05Ti0.95O3 ceramics were prepared by the seed induced method using (0.5Ba0.6Sr0.4TiO3–0.5BaZr0.05Ti0.95O3) (BST-BZT) seed. Seed crystals with concentrations of 0, 2.5, 5, 7.5, 10 mol% were mixed with BSCZT powder for 24 h and sintered at 1400 °C for 4 h. The phase formation and microstructure of BSCZT ceramic were characterized by X-ray diffraction technique (XRD) and the scanning electron microscopy (SEM). All samples showed a single phase perovskite structure without impurities and exhibited the existence of the tetragonal phase. The density values of the ceramics decreased from 4.90 to 4.75 g/cm3 with increasing seed crystal concentrations. The grain size of the sample without seed was 3.71 μm, whereas a grain size of 8.99 μm was observed for the sample with 10 mol% seed crystal. The dielectric constant at room temperature at 1 kHz was 1831 for the sample with 10 mol% seed crystal while the dielectric constant of the sample without seed was 1484. From the results in this work, BST-BZT seed can increase grain size and improve the dielectric constant at room temperature.

Sign in / Sign up

Export Citation Format

Share Document