scholarly journals Structure, Defects and Microwave Dielectric Properties of Al-doped and Al/Nd Co-doped Ba4Nd9.33Ti18O54 Ceramics

2021 ◽  
Author(s):  
Weijia Guo ◽  
Zhiyu Ma ◽  
Yu Luo ◽  
Yugu Chen ◽  
Zhenxing Yue ◽  
...  
Keyword(s):  
Dielectric Properties ◽  
Resonant Frequency ◽  
Microwave Dielectric Properties ◽  
Relative Dielectric Constant ◽  
Doping Amount ◽  
Solid State Method ◽  
Depolarization Current ◽  
Structure Defects ◽  
Microwave Dielectric ◽  
Co Doped

Abstract Ba4Nd9.33Ti18-zAl4z/3O54 (BNT-A, 0 ≤ z ≤ 2) and Ba4Nd9.33+z/3Ti18-zAlzO54 (BNT-AN, 0 ≤ z ≤ 2) ceramics were prepared by solid state method, and the effects of the two doping methods on microwave dielectric properties were compared. As the doping amount z increased, the relative dielectric constant (εr) and the temperature coefficient of resonant frequency (τf) values of the ceramics decreased, and the quality factor (Q, usually expressed by Q×f, where f is the resonant frequency) of the ceramics obviously increased when z ≤ 1.5. With the same z value, the εr and Q×f values of Al/Nd co-doped ceramics are both higher than those of Al-doped ceramics. Rietveld refinement, Raman spectroscopy and thermally stimulated depolarization current (TSDC) technique were applied to clarify the relationship among the structure, defects and microwave dielectric properties. It is shown that the Q×f values of those ceramics were closely related to the strength of the A-site cation vibration and the concentration of oxygen vacancies (B). Excellent microwave dielectric properties of εr = 72.2, Q×f = 16480 GHz, and τf = +14.3 ppm/℃ were achieved in BNT-AN ceramics with z = 1.25.

scholarly journals Structure, Defects and Microwave Dielectric Properties of Al-Doped and Al/Nd Co-doped Ba4Nd9.33Ti18O54 Ceramics

2021 ◽  
Author(s):  
Weijia Guo ◽  
Zhiyu Ma ◽  
Yu Luo ◽  
Yugu Chen ◽  
Zhenxing Yue ◽  
...  
Keyword(s):  
Dielectric Properties ◽  
Tungsten Bronze ◽  
Microwave Dielectric Properties ◽  
Dielectric Materials ◽  
Microwave Dielectric Ceramics ◽  
Solid State Method ◽  
Depolarization Current ◽  
Co Doping ◽  
Microwave Dielectric ◽  
Dielectric Ceramics

Abstract Low-loss tungsten-bronze microwave dielectric ceramics are a kind of dielectric materials with potential application value for miniaturized dielectric filters and antennas in 5G communication technology. In this work, a novel Al/Nd co-doping method of Ba4Nd9.33Ti18O54 (BNT) ceramics with a chamical formula of Ba4Nd9.33+z/3Ti18-zAlzO54 (BNT-AN, 0 ≤ z ≤ 2) was proposed to improve the dielectric properties through structural and defect modulation. Together with Al-doped ceramics (Ba4Nd9.33Ti18-zAl4z/3O54, BNT-A, 0 ≤ z ≤ 2) for comparison, the ceramics were prepared by solid state method. It is found that Al/Nd co-doping method has a significant effect on improving the dielectric properties compared with Al doping. As the doping amount z increased, the relative dielectric constant (εr) and the temperature coefficient of resonant frequency (τf) of the ceramics decreased, and the Q×f values of the ceramics obviously increased when z ≤ 1.5. Excellent microwave dielectric properties of εr = 72.2, Q×f = 16480 GHz, and τf = +14.3 ppm/℃ were achieved in BNT-AN ceramics with z = 1.25. Raman spectroscopy and thermally stimulated depolarization current (TSDC) technique were firstly combined to analyze the structure and defects in the dielectric ceramics. It is shown that the improvement on Q×f values were origined from the decrease in the strength of the A-site cation vibration and the concentration of oxygen vacancies (Vö), demonstrating the effect and mechanism underlying for structural and defect modulation on the performance improvement of microwave dielectric ceramics.

scholarly journals Effects of (Mg1/3Sb2/3)4+ Substitution on the Structure and Microwave Dielectric Properties of Ce2Zr3x(Mg1/3Sb2/3)3-3x(MoO4)9 Ceramics

2020 ◽  
Author(s):  
Zhou Xu ◽  
Sun Jiajia ◽  
Zhang Ningkang ◽  
Sun Huazhang ◽  
Tao Wenhong ◽  
...  
Keyword(s):  
Dielectric Properties ◽  
Single Phase ◽  
Microwave Dielectric Properties ◽  
Far Infrared ◽  
Structural Refinement ◽  
X Ray Diffraction ◽  
Solid State Method ◽  
Microwave Dielectric ◽  
Refinement Method ◽  
Traditional Solid State Method

Abstract Ce2[Zr1-x(Mg1/3Sb2/3)x]3(MoO4)9 (0.02≤x≤0.10) ceramics were prepared well through the traditional solid-state method. A single phase, belonging to the space group of R-3c, was detected by using X-ray diffraction at sintering temperatures ranging from 700 to 850 °C. The crystallization micro-structural of specimens was examined by applying Scanning electron microscopy. The structural refinement of these samples was investigated in detail by performing the Rietveld refinement method. The intrinsic properties were calculated and explored via far-infrared reflectivity spectroscopy. The correlations between the chemical bonds parameters and microwave dielectric properties were calculated and analyzed by P-V-L theory. Ce2[Zr0.94(Mg1/3Sb2/3)0.06]3(MoO4)9 ceramics with excellent dielectric properties: εr = 10.37, Q×f = 71748 GHz and τf = −13.6 ppm/°C sintered at 725 °C for 6 hours.

HIGH THERMAL STABILITY OF MICROWAVE DIELECTRIC PROPERTIES OF CaTi1-x(Nb1/2Fe1/2)xO3 CERAMICS

2011 ◽  
Vol 01 (04) ◽  
pp. 417-427 ◽  
Author(s):  
A. D. S. BRUNO COSTA ◽  
M. C. ROMEU ◽  
R. C. S. COSTA ◽  
T. S. M. FERNANDES ◽  
F. W. DE O. AMARANTE ◽  
...  
Keyword(s):  
Dielectric Properties ◽  
Dielectric Permittivity ◽  
Solid Solutions ◽  
Microwave Dielectric Properties ◽  
Titanium Content ◽  
Milling Process ◽  
Solid State Method ◽  
Small Shift ◽  
X Ray ◽  
Microwave Dielectric

This paper presents a study of the structure and microwave properties of [Formula: see text] substituted into the Ti 4+ site of calcium titanate ceramics. The structural and dielectric properties of solid solutions in CaTi 1-x( Nb 1/2 Fe 1/2)x O 3, was done. The microwave dielectric properties of solid solutions in CaTi 1-x( Nb 1/2 Fe 1/2)x O 3, (CNFTOX with x = 0.1 to x = 1) is discussed. The modified CaTiO3 (CTO) ceramics were prepared by a new procedure in the solid-state method. A study of the variations of the ball-milling process was done. The calcinations were done at 900°C for 3 and 5 h respectively, and the sintering at 1100°C, for 3 h. The structural property studies of the ceramics were investigated by X-ray diffraction (XRD) and Raman spectroscopy. The X-ray analysis showed that all samples have an orthorhombic structure. The refinement analysis of all samples were also duly performed and discussed. The nine scattering bands centered at 183, 227, 247, 288, 338, 470, 490 and 805 cm-1 were observed. Several peaks presented a small shift as a function of the x value. All Raman spectra in the studied samples showed a small band at 805 cm-1, which is a function of the x value. The dielectric permittivity and loss at microwave frequencies (MW) were investigated. For both calcination treatments (900°C for 3 and 5 h), the dielectric permittivity decreased with a decrease of the titanium content. Dielectric permittivity values in the range of 20 to 80 were obtained. It was also observed that a higher number of balls in the milling process contribute to the increase of the εr values. The CNFTO has an excellent microwave property at x = 0.6, with a temperature coefficient of resonant frequency (τf) near zero (τf = 2.8 ppm/°C).

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.

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.

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