DEPENDENCE OF MICROWAVE DIELECTRIC PROPERTIES ON STRUCTURAL CHARACTERISTICS OF ILMENITE, TRI-RUTILE AND WOLFRAMITE CERAMICS

2011 ◽  
Vol 01 (01) ◽  
pp. 127-134 ◽  
Author(s):  
EUNG SOO KIM ◽  
CHANG JUN JEON
Keyword(s):  
Dielectric Constant ◽  
Dielectric Properties ◽  
Structural Characteristics ◽  
Microwave Dielectric Properties ◽  
Oxygen Octahedra ◽  
Microwave Frequencies ◽  
Microwave Dielectric ◽  
Oxygen Ion ◽  
Octahedral Cation ◽  
Octahedral Distortion

Effects of crystal structures on dielectric properties of ATiO 3 (trigonal ilmenite), ATa 2 O 6 (tetragonal tri-rutile) and AWO 4 (monoclinic wolframite) (A = Ni, Mg, Co) ceramics with A- and B-site oxygen octahedra were investigated at microwave frequencies. The dielectric constant (K) of the specimens was affected by the dielectric polarizabilities of composition and cation bond valence between octahedral cation and oxygen ion per molar volume (V m ). The quality factor (Qf) of ATiO 3 was appreciably larger than those of ATa 2 O 6 and AWO 4 due to the different sharing types of oxygen octahedra. The temperature coefficient of resonant frequency (TCF) of the specimens was dependent on the octahedral distortion per V m .

DIELECTRIC PROPERTIES OF Ca(1-x)ZnxLa4Ti5O17 CERAMICS AT MICROWAVE FREQUENCIES

2009 ◽  
Vol 23 (06n07) ◽  
pp. 1179-1184 ◽  
Author(s):  
Yih-Chien Chen ◽  
Jian-Min Tsai
Keyword(s):  
Dielectric Constant ◽  
Dielectric Properties ◽  
Resonant Frequency ◽  
Microwave Dielectric Properties ◽  
Maximum Density ◽  
Zero Temperature ◽  
Microwave Frequencies ◽  
Microwave Dielectric ◽  
Diffraction Peaks ◽  
Quality Factor Q

In this paper, the microwave dielectric properties of Ca (1- x ) Zn x La 4 Ti 5 O 17 ceramics have been studied. The diffraction peaks of Ca (1- x ) Zn x La 4 Ti 5 O 17 ceramics shift to higher angles as x increases from 0 to 0.01 and nearly unchanged with x increasing from 0.01 to 0.03. A maximum density of dielectric constant value of 57 and a quality factor ( Q × f ) of 15000 GHz can be obtained for Ca 0.99 Zn 0.01 La 4 Ti 5 O 17 ceramic sintered at 1450°C for 4h. A near-zero temperature coefficient of resonant frequency (τ f ) of -8.1 ppm/°C can be obtained for Ca 0.99 Zn 0.01 La 4 Ti 5 O 17 ceramic sintered at 1450°C for 4h.

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.

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.

Dielectric Properties of a New Ceramic System (1-x)(Mg0.95Zn0.05)2TiO4-x(Ca0.8Sr0.2)TiO3 at Microwave Frequencies

2020 ◽  
Vol 830 ◽  
pp. 37-42
Author(s):  
Shih Sheng Liu ◽  
Shiuan Ho Chang ◽  
Yuan Bin Chen
Keyword(s):  
Dielectric Properties ◽  
Microwave Dielectric Properties ◽  
Second Phase ◽  
X Ray Diffraction ◽  
Low Loss ◽  
Microwave Frequencies ◽  
Solid State Route ◽  
Microwave Dielectric ◽  
System 1 ◽  
Quality Factor Q

The microwave dielectric properties and microstructures of the (1-x)(Mg0.95Zn0.05)2TiO4-x (Ca0.8Sr0.2)TiO3 ceramics prepared using the conventional solid-state route were investigated. The structure and microstructure were analyzed by X-ray diffraction (XRD) and scanning electron microscopy (SEM), respectively. Ilmenite-structured (Mg0.95Zn0.05)TiO3 was detected as a second phase. The coexistence of the second phase, however, did not degrade the dielectric properties of the specimen because the phases were compatible. At x = 0.07, a dielectric constant (εr) of ~17.86, a quality factor (Q×f) value of ~ Q×f~133,600 Hz (at 10 GHz), and a temperature coefficient of resonant frequency (τf) of ~ –5ppm/°Cwere obtained for 0.93(Mg0.95Zn0.05)2TiO4-0.07(Ca0.8Sr0.2)TiO3 ceramic sintered at 1240°C for 4 hr. The dielectric is proposed as a candidate material for low-loss microwave and millimeter wave applications.

Effects of Nd2O3 on the microwave dielectric properties of BiNbO4 ceramics

1998 ◽  
Vol 13 (10) ◽  
pp. 2945-2949 ◽  
Author(s):  
Whan Choi ◽  
Kyung-Yong Kim ◽  
Myung-Rip Moon ◽  
Kyoo-Sik Bae
Keyword(s):  
Dielectric Constant ◽  
Dielectric Properties ◽  
Resonance Frequency ◽  
Sintering Temperature ◽  
Microwave Dielectric Properties ◽  
Positive Direction ◽  
Microwave Dielectric ◽  
Triclinic Phase ◽  
Nd Substitution ◽  
Peak Value

Effects of Nd substitution with Bi on the microwave dielectric properties of BiNbO4 were studied. Bi1−xNdxNbO4 ceramics sintered at 920–980 °C consisted of orthorhombic and triclinic phases. The amount of triclinic phase increased with the increase in the Nd content, x, and sintering temperature. The apparent density and the dielectric constant decreased with the Nd content, but increased with sintering temperature, reached the peak values at 960 °C and then rapidly decreased. The Q × f0 value was between 11,000 and 13,000 GHz over all sintering temperatures for x < 0.05, but for x ≥ 0.05 it reached the peak value at 950 °C and then rapidly decreased. The temperature coefficient of resonance frequency increased in the positive direction with the Nd content and showed the minimum value of −1.82 ppm/°C for x = 0.025 sintered at 940 °C. However, it rapidly increased in the negative direction for sintering temperature over 960 °C.

Effect of Thermal Stress on the Microwave Dielectric Properties of (300-X) nm MgTiO3 /(X) nm CaTiO3 Thin Films

2006 ◽  
Vol 45 ◽  
pp. 2332-2336
Author(s):  
Ki Hyun Yoon ◽  
Ji Won Choi
Keyword(s):  
Thin Films ◽  
Dielectric Constant ◽  
Thermal Expansion ◽  
Thermal Stress ◽  
Dielectric Properties ◽  
Dielectric Loss ◽  
Microwave Dielectric Properties ◽  
Mixing Rule ◽  
Microwave Dielectric ◽  
Dielectric Layers

The microwave dielectric properties of (300-X) nm MgTiO3/(X) nm CaTiO3 thin films have been investigated with correlation between the interface and stress induced by dielectric layers with heattreatment. As the thickness (X) of CaTiO3 film increased, the dielectric constant increased and the temperature coefficient of the dielectric constant changed from the positive to the negative values by the dielectric mixing rule. The dielectric loss of (300-X) nm MgTiO3/(X) nm CaTiO3 thin films increased with an increase of the thickness (X) of CaTiO3 film because of higher thermal stress induced by the higher thermal expansion coefficient of CaTiO3 than that of MgTiO3.

B-O Bond Character and Microwave Dielectric Properties of (1-x)CaTiO3-xCa(Zn1/3Nb2/3)O3 Perovskite Ceramics

2009 ◽  
Vol 421-422 ◽  
pp. 69-72
Author(s):  
Jie Shen ◽  
Wen Chen ◽  
Jing Zhou ◽  
Jie Zhu ◽  
Qiong Lei
Keyword(s):  
Dielectric Constant ◽  
Dielectric Properties ◽  
Microwave Dielectric Properties ◽  
Dielectric Materials ◽  
Solid State Reaction Method ◽  
Dielectric Constants ◽  
Identical Result ◽  
Microwave Dielectric ◽  
Calculation Results ◽  
The Relationship

The relationship between the character of the B-site cation–oxygen bond and the microwave dielectric properties in perovskites dielectric materials was studied in this paper. The atomic net charge of CaTiO3 (CT) and Ca(Zn1/3Nb2/3)O3 (CZN) was calculated respectively. The calculating result implies that the covalency of B-O bonds in CZN is stronger than that in CT. This predicted that the dielectric constant and loss of the ceramics will decrease after CZN incorporated in CT. To confirme the prediction, (1-x)CT-xCZN microwave dielectric ceramics were prepared by solid state reaction method with ZnNb2O6 as precursor. The structure analysis in terms of tolerance factor gives an identical result as calculation. The microwave dielectric properties, such as dielectric constants, Q×f values and τf were studied as a function of composition. With x increasing from 0.2 to 0.8, the dielectric constant linearly decreases from 109 to 49.37, the Q×f value increases from 8,340 to 13,200 GHz, and τf decreases from 321 to -18 ppm/°C. The properties trends are consistent with the previous calculation results, and confirm the relationship between the character of B-O bond and dielectric properties.

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