Dielectric Properties of Cr2O3 Doped (Ba,Sr,Ca)TiO3 Ceramics for Tunable Microwave Devices

2006 ◽  
Vol 966 ◽  
Author(s):  
Bing Qin ◽  
Dengren Jin ◽  
Jinrong Chen ◽  
Zhongyan Meng
Keyword(s):  
Dielectric Constant ◽  
Dielectric Properties ◽  
Dielectric Loss ◽  
Curie Temperature ◽  
Mixed Oxide ◽  
Dopant Concentration ◽  
Homogeneous Structure ◽  
Microwave Devices ◽  
Thermal Stabilities ◽  
Dielectric Constant And Loss

ABSTRACTCr2O3-doped (Ba0.55Sr0.4Ca0.05)TiO3 ceramics were fabricated by the mixed-oxide method. Their dielectric properties were investigated with the variation of Cr3+ doping concentrations (0∼2.0mol%). All the BSCT specimens owned dense and homogeneous structure. Doping of Cr3+ could reduce the Curie temperature and their dielectric constant peak values, and improve the thermal stabilities of their dielectric properties. Both the dielectric constant and dielectric loss of the BSCT ceramics were reduced by doping Cr ions when the dopant concentration was lower than 1.5mol%. 1.0mol% Cr-doped BSCT specimens are expected to be the candidate materials for microwave tunable devices, whose tunability, dielectric constant and loss were 16.1%, 2700 and 0.24% respectively.

Synthesis and Characteristics of MgO Coated BST-Mg2TiO4 Composite Ceramics

2012 ◽  
Vol 512-515 ◽  
pp. 1180-1183
Author(s):  
Qian Qian Jia ◽  
Hui Ming Ji ◽  
Shan Liu ◽  
Xiao Lei Li ◽  
Zheng Guo Jin
Keyword(s):  
Dielectric Constant ◽  
Dielectric Properties ◽  
Curie Temperature ◽  
Loss Tangent ◽  
Phase Shifters ◽  
Precipitation Method ◽  
Composite Ceramics ◽  
Low Dielectric ◽  
Dielectric Constant And Loss ◽  
Bst Ceramics

The (Ba, Sr)TiO3 (hereafter BST) ceramics are promising candidate for applying in tunable devices. MgO coated BST-Mg2TiO4 (BSTM-MT) composite ceramics were prepared to obtain the low dielectric constant, low dielectric loss, good dielectric constant temperature stability, and high tunability of BST ceramics. The Ba0.55Sr0.40Ca0.05TiO3 nanoparticles were coated with MgO using the precipitation method and then mixed with Mg2TiO4 powders to fabricate BSTM-MT composite ceramics. The morphologies, phases, elements, and dielectric properties of the sintered ceramics were investigated. The core-shell structure of BST powder wrapped with MgO was clearly observed from the TEM image. After sintered at 1100 °C for 2 h, the composite ceramics expressed dense microstructures from SEM images and two main phases BST and Mg2TiO4 were detected in the XRD patterns. The dielectric constant and loss tangent were both reduced after the coating. The reduced dielectric constant and loss tangent of BSTM-MT were 190, 0.0011 (2MHz), respectively. The ceramics exhibited the diffuse phase transition near the Curie temperature and the Curie temperature shifted from 10 °C to 5 °C after the coating. Since the continuous Ti-O bonds were disconnected with the MgO coating, the tunability was reduced to 15.14 % under a DC bias field of 1.1 kV/mm. The optimistic dielectric properties made it useful for the application of tunable capacitors and phase shifters.

Influence of Ti content and sintering temperature on dielectric properties of Bi4Ti3O12 ceramics

2017 ◽  
Vol 31 (16-19) ◽  
pp. 1744057 ◽  
Author(s):  
Yong Chen ◽  
Zhaozhi Li ◽  
Huyin Su ◽  
Simin Xue ◽  
Mengyun Bian ◽  
...  
Keyword(s):  
Dielectric Constant ◽  
Dielectric Properties ◽  
Dielectric Loss ◽  
Curie Temperature ◽  
Relative Permittivity ◽  
Dielectric Material ◽  
Perovskite Phase ◽  
Layered Perovskite ◽  
Microwave Ceramics ◽  
Ti Content

An ultra-broad working temperature dielectric material, Bi4Ti[Formula: see text]O[Formula: see text]([Formula: see text] = 2.96, 2.98, 3.0, 3.02 and 3.04), prepared by a conventional mixed oxide route was investigated which is supposed to replace lead-containing ceramics for its outstanding dielectric properties. Microstructure and dielectric properties of well-sintered samples (at 1040[Formula: see text]C, 1060[Formula: see text]C, 1080[Formula: see text]C, 1100[Formula: see text]C and 1120[Formula: see text]C) were studied. X-ray diffraction analysis indicated that the new material was in a single Bi-layered perovskite phase. The dielectric constant and dielectric loss at different frequencies (10, 100 and 1000 kHz) were measured at 1100[Formula: see text]C. With the increasing frequency, the dielectric constant decreased and the dielectric loss was almost unchanged. While at 100 kHz, there is the highest relative permittivity ([Formula: see text]) of 2822.8 and the lowest dielectric loss of 0.0040 ([Formula: see text] = 2.98), the Curie temperature ([Formula: see text]) is 668.9[Formula: see text]C. At the frequency of 1 MHz, the highest relative permittivity ([Formula: see text]) is 1115.8 when Ti content is 3.02, and the Curie temperature is 672.2[Formula: see text]C. SEM can explain the results of the dielectric spectrum at different Ti content and sintering temperatures. [Formula: see text] plots show that Bi4Ti3O[Formula: see text] ceramics are a kind of dielectrics. Since it possesses large dielectric constant, low dielectric loss and stable temperature character, this material shows promising applications for the ultra-broad temperature range components, such as high-temperature multilayer ceramic capacitors and microwave ceramics.

EFFECT OF MgO ON STRUCTURE AND DIELECTRIC PROPERTIES OF CaO–Al2O3–B2O3–SiO2 GLASSES

2012 ◽  
Vol 19 (06) ◽  
pp. 1250063 ◽  
Author(s):  
ZHAO DU ◽  
XUEHONG ZHANG ◽  
YUNLONG YUE ◽  
HAITAO WU
Keyword(s):  
Dielectric Constant ◽  
Dielectric Properties ◽  
Dielectric Loss ◽  
Glass Network ◽  
Glass System ◽  
Dielectric Constant And Loss ◽  
Lower Dielectric Constant

The effect of MgO on structure and dielectric properties of aluminoborosilicate glasses was investigated. FTIR data indicated that glass network was mainly built by tetrahedral [ SiO4 ], [ BO4 ], [ AlO4 ] and trigonal [ BO3 ]. A small amount of AlO5 or AlO6 units also existed. The glass system was characterized with lower dielectric constant (4.17 ~ 4.6) and dielectric loss (12.3 × 10-4 ~ 14.77 × 10-4) at 1 MHz. With the increase of MgO content, the quantity of AlO5 or AlO6 units decreased. The variation of density showed a decreasing tendency. The dielectric constant and loss were all found to decrease.

The Influence of La2O3 Additive on the Dielectric Properties of Ba0.6Sr0.4TiO3-MgO Bulk Ceramics

2007 ◽  
Vol 336-338 ◽  
pp. 249-251
Author(s):  
Chun Lai Xu ◽  
He Ping Zhou
Keyword(s):  
Dielectric Constant ◽  
Dielectric Properties ◽  
Dielectric Loss ◽  
High Frequency ◽  
Doping Content ◽  
Dielectric Constant And Loss ◽  
Lower Dielectric Constant ◽  
Excess Quantity

The influence of La2O3-doping on the dielec- tric properties of Ba0.6Sr0.4TiO3-6wt%MgO was studied. With the increase of La2O3-doping content, the space between adjacent parallel crystal planes of BST-MgO composite first became larger, then smaller. Proper quantity of La2O3 could ensure moderate dielectric constant and reduce the dielectric loss of BST-MgO composite at high frequency, but excess quantity of La2O3 would lower dielectric constant. When the La2O3-doping content was 0.2wt%, the dielectric constant and loss of BST-MgO composite were equal to 93.2 and 0.005 (1MHz), respectively. And the dielectric constant tunability could be obtained to 12.1% (21kV/cm).

Microstructure and Microwave Dielectric Properties of BaTi4O9 Ceramics Derived from a Sol-Gel Precursor

2011 ◽  
Vol 326 ◽  
pp. 127-130
Author(s):  
Xian Li Huang ◽  
Fu Ping Wang ◽  
Ying Song
Keyword(s):  
Dielectric Constant ◽  
Dielectric Properties ◽  
Dielectric Loss ◽  
Sol Gel ◽  
Microwave Dielectric Properties ◽  
Sintering Process ◽  
Temperature Coefficients ◽  
Microwave Dielectric ◽  
Ceramic Samples ◽  
Quality Factor Q

In the present work, the microstructure and microwave dielectric properties of BaTi4O9 ceramics derived from a sol-gel precursor were presented. Density measuring results demonstrated that the largest densities of ceramic sample about 96.7% could be reached by virtue of a cool iso-static press and a sintering process at at 1300 °C for 6 hours. The dielectric constant (εr), quality factor (Q×f) and the temperature coefficients (τf) of the BaTi4O9 ceramic samples were 36.65, 28000 GHz, +20.2 ppm/°C, respectively. XRD, SEM and XPS were used to characterize the microstructure of the ceramics samples. Substantial Ti3+ was proposed to be the cause of dielectric loss.

Preparation and Properties of Silicon-Containing Arylacetylene Resins with Octa(maleimidophenyl)silsesquioxane

2012 ◽  
Vol 557-559 ◽  
pp. 1152-1156
Author(s):  
Yan Zhou ◽  
Fu Wei Huang ◽  
Fa Rong Huang ◽  
Lei Du
Keyword(s):  
Thermal Stability ◽  
Dielectric Constant ◽  
Dielectric Properties ◽  
Thermal Polymerization ◽  
Curing Process ◽  
Thermal Stabilities ◽  
Curing Reaction ◽  
Air Atmosphere ◽  
Ft Ir ◽  
Dsc Analyses

Modified silicon-containing arylacetylene resins (DMSEPE-OMPS) were prepared from poly(dimethylsilyleneethynylenephenyleneethynylene) (DMSEPE) and Octa(maleimidophenyl)- silsesquioxane (OMPS). The curing reaction of DMSEPE-OMPS resin was studied by FT-IR and DSC techniques. Thermal stability and dielectric properties of cured DMSEPE-OMPS resins were determined. FT-IR and DSC analyses indicate that thermal polymerization of DMSEPE-OMPS resin occurs in the curing process. Thermal stabilities of cured DMSEPE-OMPS resins under N2 and air atmosphere decrease gradually with the increment of OMPS components. The incorporation of OMPS can obviously reduce dielectric constant of DMSEPE-OMPS resins.

Preparation and Dielectric Properties of 1-3 La Modified PZT/IPN Piezoelectric Composites

2010 ◽  
Vol 105-106 ◽  
pp. 355-358 ◽  
Author(s):  
Z.L. Zhu ◽  
Dong Yan Tang ◽  
X.H. Zhang ◽  
Y.J. Qiao
Keyword(s):  
Heat Treatment ◽  
Dielectric Constant ◽  
Dielectric Properties ◽  
Dielectric Loss ◽  
Lead Zirconate Titanate ◽  
Polymer Network ◽  
Lead Zirconate ◽  
Interpenetrating Polymer Network ◽  
Ceramic Fibers ◽  
Piezoelectric Composites

To prevent the potential cracking of gel fibers, La modified lead zirconate titanate (PLZT) ceramic fibers with diameter within 50µm were achieved by embedding into PLZT powders during the heat treatment. Then the 1-3 PLZT fiber/interpenetrating polymer network (IPN) piezoelectric composites were prepared by casting the IPN precursors onto the well aligned ceramic fibers. The influences of the heating temperatures and La amounts on the dielectric constant, dielectric loss with frequencies and piezoelectric constant of PLZT were investigated in detail. The morphologies of fibers and composites were observed by biological microscope. And also, the dielectric constant of PLZT fibers and PLZT fiber/IPN piezoelectric composites were detected.

Microwave Nondestructive Sensing of Moisture Content and Water Activity of Almonds

2021 ◽  
Vol 64 (4) ◽  
pp. 1373-1379
Author(s):  
Samir Trabelsi
Keyword(s):  
Dielectric Constant ◽  
Dielectric Properties ◽  
Dielectric Loss ◽  
Moisture Content ◽  
Bulk Density ◽  
Water Activity ◽  
Free Space ◽  
Loss Factor ◽  
Dielectric Loss Factor ◽  
List Type

HighlightsMoisture and water activity were determined nondestructively and in real time from measurement of dielectric properties.Moisture and water activity calibration equations were established in terms of the dielectric properties.Situations in which bulk density was known or unknown were considered.SEC ranged from 0.41% to 0.68% for moisture and from 0.02 to 0.04 for water activity.Abstract. A method for rapid and nondestructive determination of moisture content and water activity of granular and particulate materials was developed. The method relies on measurement of the dielectric constant and dielectric loss factor at a single microwave frequency. For the purpose of illustration, the method was applied to predicting the moisture content and water activity of almond kernels. A free-space transmission technique was used for accurate measurement of the dielectric properties. Samples of Bute Padre almond kernels with moisture content ranging from 4.8% to 16.5%, wet basis (w.b.), and water activity ranging from 0.50 to 0.93 were loaded into a Styrofoam sample holder and placed between two horn-lens antennas connected to a vector network analyzer. The dielectric properties were calculated from measurement of the attenuation and phase shift at 8 GHz and 25°C. The dielectric properties increased linearly with moisture content, while they showed an exponential increase with water activity. Situations in which the bulk density was known and unknown were considered. Linear and exponential growth regressions provided equations correlating the dielectric properties with moisture content and water activity with coefficients of determination (r2) higher than 0.96. Analytical expressions of moisture content and water activity in terms of the dielectric properties measured at 8 GHz and 25°C are provided. The standard error of calibration (SEC) was calculated for each calibration equation. Results show that moisture content can be predicted with SECs ranging from 0.41% to 0.68% (w.b.) and water activity with SECs ranging from 0.02 to 0.04 for almond kernel samples with water activity ranging from 0.5 to 0.9 and moisture contents ranging from 4.8% to 16.5% (w.b.). Keywords: Bulk density, Dielectric constant, Dielectric loss factor, Free-space measurements, Loss tangent, Microwave frequencies, Moisture content, Water activity.

Synthesis and Dielectric Properties of [(K0.5Na0.5)0.935Li0.065]NbO3 Added with Mn for Piezoelectric Ceramic

2016 ◽  
Vol 675-676 ◽  
pp. 635-638
Author(s):  
Jukkrit Kongphimai ◽  
Hassakorn Wattanasarn ◽  
Tosawat Seetawan
Keyword(s):  
Crystal Structure ◽  
Dielectric Constant ◽  
Dielectric Properties ◽  
Dielectric Loss ◽  
Physical Properties ◽  
Crystallite Size ◽  
Piezoelectric Ceramic ◽  
Theoretical Density ◽  
Milling Method ◽  
Xrd Patterns

[(K0.5Na0.5 )0.935Li0.065]NbO3–Mn ceramics (Mn = 0, 1.50 and 3 mol %) (KNNL–Mn) were synthesized and measured dielectric properties. Which the K2CO3, Na2CO3, Li2CO3, Nb2O5 and MnO2 (0, 1.5, 3 mol%) were mixed by ball milling method and calcined powders at 1,073 K for 4 h and the sintered at 1,343 K for 2 h in air. The crystal structure was analyzed by XRD technique, the crystallite size was identified by Scherrer’s equation and calculated the theoretical density. It was found that, the XRD patterns of the KNNL–Mn ceramics added with Mn contents was indicated the tetragonal structure and. the crystallite size of Mn = 0, 1.50 and 3 mol% about 32 nm, 34 nm and 57 nm, respectively. The physical properties of the KNNL–Mn ceramics was found that the maximum theoretical density of 90.79 % for Mn = 1.50 mol%. The dielectric constant was found to be maximum of 909.77 and dielectric loss of 0.48 for Mn = 3 mol%.

Effect of moisture content on dielectric properties of banana leaves and peels in frequency range of 1–20 GHz

Frequenz ◽  
2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Soumya Sundar Pattanayak ◽  
Soumen Biswas
Keyword(s):  
Dielectric Constant ◽  
Dielectric Properties ◽  
Dielectric Loss ◽  
Moisture Content ◽  
Measurement Data ◽  
Banana Peel ◽  
Frequency Range ◽  
Proposed Model ◽  
Banana Leaves ◽  
Banana Leaf

Abstract The quality of agricultural products can be remotely sensed and enhanced by determining the dielectric properties. This paper studies the dielectric properties of banana leaf and banana peel over the frequency range 1–20 GHz using the open-ended coaxial probe (OCP) method. A new curve fitting model is proposed to characterize the dielectric properties of banana leaf and banana peel. The different moisture content (MC) levels are considered for both banana leaf and banana peel samples and, their dielectric properties are characterized. Further, the banana leaf and banana peel’s measurement data are compared with the data obtained using the proposed model. In addition, Root Mean Square Error (RMSE) and R-squared (R 2) are calculated to validate the performance of the proposed model. In case of banana leaf at 68.26% MC, the dielectric constant achieves the value of R 2 and RMSE of 0.98 and 0.0648, respectively. Similarly, dielectric loss achieves the value of R 2 and RMSE of 0.88 and 0.0795, respectively. Further, for banana peel at 80.89% MC, the dielectric constant achieves the value of R 2 and RMSE of 0.99 and 0.2989, respectively. Similarly, dielectric loss achieves the value of R 2 and RMSE of 0.96 and 0.6132, respectively.

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