Structures and microwave dielectric properties of Ba6−3x(Nd,Biy)8+2xTi18O54 (x = 2/3) solid solution

2001 ◽  
Vol 16 (6) ◽  
pp. 1734-1738 ◽  
Author(s):  
Yong Jun Wu ◽  
Xiang Ming Chen
Keyword(s):  
Solid Solution ◽  
Dielectric Properties ◽  
Resonant Frequency ◽  
Temperature Coefficient ◽  
Solid Solubility ◽  
Microwave Dielectric Properties ◽  
Solubility Limit ◽  
Solid Solubility Limit ◽  
Continuous Increase ◽  
Microwave Dielectric

The effects of Bi substitution for Nd in Ba6−3xNd8+2xTi18O54 (x = 2/3) solid solution upon the microstructures and microwave dielectric properties were investigated. The solid solubility limit of Bi in Ba6−3xNd8+2xTi18O54 (x = 2/3) solid solution was about 15 mol%, the same as that for x = 0.5, and densification of the present solid solutions could be performed well at lower temperatures. However, the variation tendency of microwave dielectric properties with composition in the present ceramics quite differed from that for x = 0.5: (1) The temperature coefficient of resonant frequency in the present ceramics showed a continuous variation from positive to negative and did not indicate extreme value at the solid solubility limit. (2) Near-zero temperature coefficient of resonant frequency combined with high-ε and high-Qf values could be obtained in the present ceramics, while that for x = 0.5 had a lower limit of +15 ppm/°C. (3) The dielectric constant also showed a continuous increase for the present compositions, while that in x = 0.5 had an extreme at solid solubility limit. Ceramics with composition of Ba6−3x(Nd0.85,Bi0.15)8+2xTi18O54 (x = 2/3) showed excellent dielectric properties of ε = 99.1, Qf = 5290 GHz, and τf = −5.5 ppm/°C.

Role of Bi2O3 in optimizing the dielectric properties of Ba4.5Nd9Ti18O54 based microwave ceramics

1996 ◽  
Vol 11 (4) ◽  
pp. 928-931 ◽  
Author(s):  
Matjaž Valant ◽  
Danilo Suvorov ◽  
Drago Kolar
Keyword(s):  
Solid Solution ◽  
Dielectric Properties ◽  
Resonant Frequency ◽  
Temperature Coefficient ◽  
Bismuth Titanate ◽  
Solubility Limit ◽  
Microwave Ceramics ◽  
Solid Solubility Limit ◽  
Microwave Frequencies

Small additions of Bi2O3 or bismuth titanate improve the dielectric properties of Ba4.5Nd9Ti18O54 at microwave frequencies. It was found that Bi3+ can replace Nd3+ up to 15 mol%, the limiting composition of solid solution being Ba4.5(Nd0.85Bi0.15)9Ti18O54. At the solid solution limit the temperature coefficient of resonant frequency attains its minimum value. The modified ceramic is distinguished by high permittivity of 99 and a Q-value of 5500. The temperature coefficient of resonant frequency is low, 15 ppm/K. After exceeding the solid solubility limit, additional Bi2O3 concentrates as a Bi-rich phase at the grain boundaries, causing considerable reduction of the Q-value and an increase of τf.

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.

Microwave dielectric properties of (Zr0.8Sn0.2)TiO4 ceramics with pentavalent additives

1995 ◽  
Vol 10 (8) ◽  
pp. 2085-2090 ◽  
Author(s):  
Ki Hyun Yoon ◽  
Young Sol Kim ◽  
Eung Soo Kim
Keyword(s):  
Dielectric Properties ◽  
Resonant Frequency ◽  
Temperature Coefficient ◽  
Electron Concentration ◽  
Oxygen Vacancies ◽  
Microwave Dielectric Properties ◽  
Temperature Range ◽  
Microwave Dielectric ◽  
Ionic Size

The microwave dielectric properties of (Zr0.8Sn0.2)TiO4 were investigated as a function of the amount of additives such as Nb2O5 Ta2O5 and Sb2O5 in the temperature range of 20 °C to 80 °C at 7 GHz. As the amount of additives increased up to 1.0 mol %, the unloaded Q increased due to the decrease of oxygen vacancies in the (Zr0.8Sn0.2)TiO4 lattice and then decreased with further addition of additives because the electron concentration was increased. The temperature coefficient of the resonant frequency turned more negative with increasing additives. Although the Nb+5, Ta+5, and Sb+5 ions have a similar ionic size and the same valence electronics, each resulted in different microwave dielectric properties.

Dielectric properties of La-substituted Pb0.5Ca0.5[(Mg1/3Nb2/3)0.5Ti0.5]O3 ceramics

2001 ◽  
Vol 16 (7) ◽  
pp. 2053-2056
Author(s):  
X. J. Lu ◽  
X. M. Chen
Keyword(s):  
Dielectric Constant ◽  
Dielectric Properties ◽  
Resonant Frequency ◽  
Temperature Coefficient ◽  
Microwave Dielectric Properties ◽  
Present Approach ◽  
Calculated Temperature ◽  
Microwave Dielectric ◽  
La Substitution ◽  
Dielectric Ceramics

Modification of Pb0.5Ca0.5[(Mg1/3Nb2/3)0.5Ti0.5]O3 dielectric ceramics was performed by up to 20 mol% La substitution for Pb and Ca. The temperature coefficient of dielectric constant was significantly reduced by the present approach, while an increased Qf factor was achieved. Good microwave dielectric properties were obtained in a composition Pb0.425Ca0.425La0.1[(Mg1/3Nb2/3)0.5Ti0.5]O3: ε = 125; Qf = 3150 GHz; calculated temperature coefficient of resonant frequency δf = +253 ppm/°C.

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