MICROWAVE DIELECTRIC PROPERTIES AND RAMAN SPECTROSCOPY OF SCHEELITE SOLID SOLUTION [(Li0.5Bi0.5)1-xCax]MoO4 CERAMICS WITH ULTRA-LOW SINTERING TEMPERATURES

2010 ◽  
Vol 03 (04) ◽  
pp. 253-257 ◽  
Author(s):  
DI ZHOU ◽  
HONG WANG ◽  
QIU-PING WANG ◽  
XIN-GUANG WU ◽  
JING GUO ◽  
...  
Keyword(s):  
Solid Solution ◽  
Raman Spectroscopy ◽  
Dielectric Properties ◽  
Temperature Coefficient ◽  
Relative Permittivity ◽  
High Performance ◽  
Microwave Dielectric Properties ◽  
Solid State Reaction Method ◽  
X Ray Diffraction ◽  
Microwave Dielectric

A Scheelite solid solution was formed based on [( Li0.5Bi0.5 )1-x Ca x] MoO 4 ceramics and prepared via a solid state reaction method in the range 0.0 ≤ x ≤ 1.0. High performance microwave dielectric properties were obtained in the [(Li0.5Bi0.5)0.15Ca0.85]MoO4 ceramic sintered at 760°C with a relative permittivity of 14.1, a Qf value of 24,000 GHz (at 10.0 GHz), and a temperature coefficient value of +10.7 ppm/°C and the [(Li0.5Bi0.5)0.1Ca0.9]MoO4 ceramic sintered at 850°C with a relative permittivity of 12.7, a Qf value of 41,300 GHz (at 10.3 GHz), and a temperature coefficient value of -16.5 ppm/°C. X-ray diffraction, Raman spectroscopy and the classical damped oscillator model were applied to study the relationship between the microwave dielectric properties and structures.

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.

PHASE EVOLUTION AND MICROWAVE DIELECTRIC PROPERTIES OF (Li0.5Bi0.5)(W1-xMox)O4(0.0 ≤ x ≤ 1.0) CERAMICS WITH ULTRA-LOW SINTERING TEMPERATURES

2012 ◽  
Vol 05 (04) ◽  
pp. 1250042 ◽  
Author(s):  
DI ZHOU ◽  
JING GUO ◽  
XI YAO ◽  
LI-XIA PANG ◽  
ZE-MING QI ◽  
...  
Keyword(s):  
Dielectric Properties ◽  
High Performance ◽  
Microwave Dielectric Properties ◽  
Phase Evolution ◽  
Solid State Reaction Method ◽  
Ceramic Technology ◽  
Microwave Range ◽  
X Ray ◽  
Microwave Dielectric ◽  
C Complex

The ( Li 0.5 Bi 0.5)( W 1-x Mo x) O 4(0.0 ≤ x ≤ 1.0) ceramics were prepared via the solid state reaction method. The sintering temperature decreased almost linearly from 755°C for ( Li 0.5 Bi 0.5) WO 4 to 560°C for ( Li 0.5 Bi 0.5) MoO 4. When the x≤0.3, a wolframite solid solution can be formed. For x = 0.4 and x = 0.6 compositions, both the wolframite and scheelite phases can be formed from the X-ray diffraction analysis, while two different kinds of grains can be revealed from the scanning electron microscopy and energy-dispersive X-ray spectrometer results. High performance of microwave dielectric properties were obtained in the (Li0.5Bi0.5)(W0.6Mo0.4)O4 ceramic sintered at 620°C with a relative permittivity of 31.5, a Qf value of 8500 GHz (at 8.2 GHz), and a temperature coefficient value of +20 ppm/°C. Complex dielectric spectra of pure (Li0.5Bi0.5)WO4 ceramic gained from the infrared spectra were extrapolated down to microwave range, and they were in good agreement with the measured values. The ( Li0.5Bi0.5 )( W 1-x Mo x) O 4(0.0 ≤ x ≤ 1.0) ceramics might be promising for low temperature co-fired ceramic technology.

scholarly journals A low-firing melilite ceramic Ba2CuGe2O7 and compositional modulation on microwave dielectric properties through Mg substitution

2020 ◽  
Author(s):  
Changzhi Yin ◽  
Zezong Yu ◽  
Longlong Shu ◽  
Laijun Liu ◽  
Yan Chen ◽  
...  
Keyword(s):  
Crystal Structure ◽  
Dielectric Properties ◽  
Resonance Frequency ◽  
Temperature Coefficient ◽  
Quality Factor ◽  
Relative Permittivity ◽  
Microwave Dielectric Properties ◽  
Sintering Behavior ◽  
Magnesium Doping ◽  
Microwave Dielectric

AbstractA melilite Ba2CuGe2O7 ceramic was characterized by low sintering temperature and moderate microwave dielectric properties. Sintered at 960 °C, the Ba2CuGe2O7 ceramic had a high relative density 97%, a low relative permittivity (εr) 9.43, a quality factor (Q×f) of 20,000 GHz, and a temperature coefficient of resonance frequency (τf) −76 ppm/°C. To get a deep understanding of the relationship between composition, structure, and dielectric performances, magnesium substitution for copper in Ba2CuGe2O7 was conducted. Influences of magnesium doping on the sintering behavior, crystal structure, and microwave dielectric properties were studied. Mg doping in Ba2CuGe2O7 caused negligible changes in the macroscopic crystal structure, grain morphology, and size distribution, while induced visible variation in the local structure as revealed by Raman analysis. Microwave dielectric properties exhibit a remarkable dependence on composition. On increasing the magnesium content, the relative permittivity featured a continuous decrease, while both the quality factor and the temperature coefficient of resonance frequency increased monotonously. Such variations in dielectric performances were clarified in terms of the polarizability, packing fraction, and band valence theory.

Microwave dielectric properties of (1 − x)Cu3Nb2O8−xZn3Nb2O8 ceramics

2001 ◽  
Vol 16 (5) ◽  
pp. 1465-1470 ◽  
Author(s):  
Dong-Wan Kim ◽  
In-Tae Kim ◽  
Byungwoo Park ◽  
Kug Sun Hong ◽  
Jong-Hee Kim
Keyword(s):  
Solid Solution ◽  
Dielectric Properties ◽  
Microwave Dielectric Properties ◽  
Sintering Behavior ◽  
X Ray Diffraction ◽  
Two Phase ◽  
Sintering Aid ◽  
Microwave Dielectric ◽  
Solid Solution Region ◽  
Solution Region

The sintering behavior and microwave dielectric properties of (1 − x)Cu3Nb2O8−xZn3Nb2O8 have been investigated using dilatometry, x-ray diffraction, and a network analyzer. It was found that (1 − x)Cu3Nb2O8−xZn3Nb2O8 ceramics have a much lower melting temperature than Zn3Nb2O8 ceramics without Cu3Nb2O8 additives. Samples sintered at 900 °C for 2 h exhibited densities >97% of the theoretical density. Cu3Nb2O8 acts as a sintering aid. Two phase regions were identified with increasing Zn3Nb2O8 contents. A Cu3Nb2O8−Zn3Nb2O8 solid solution exists from 0 < x < 0.5 while a mixture of Cu3Nb2O8 and Zn3Nb2O8 exists from 0.5 < x < 1. The microwave dielectric properties correlated to the crystal structure. In Cu3Nb2O8−Zn3Nb2O8 solid solution region, the variation of dielectric properties could be explained by the structure distortion of Cu3Nb2O8 due to electronic anisotropies of Cu2+ cations.

Structural Evolution and Microwave Dielectric Properties of Ba(Co1/3(Nb1-xW5x/6)2/3)O3 Ceramics

2018 ◽  
Vol 281 ◽  
pp. 585-590
Author(s):  
Zhe Fei Wang ◽  
Chen Yao Zhai ◽  
Xu Hong Wang
Keyword(s):  
Dielectric Properties ◽  
Sintering Temperature ◽  
Structural Evolution ◽  
Microwave Dielectric Properties ◽  
Solid State Reaction Method ◽  
Second Phase ◽  
X Ray Diffraction ◽  
X Ray ◽  
Microwave Dielectric ◽  
Dielectric Ceramics

Ba(Co1/3(Nb1-xW5x/6)2/3)O3 (0<x≤0.05) (BCWN) microwave dielectric ceramics have been prepared by solid-state reaction method. The microstructure and microwave dielectric properties of BCWN ceramics were investigated systematically in this paper. The results show that the sintering temperature decreases with the substitution of W6+. The Ba(Co1/3(Nb1-xW5x/6)2/3)O3 solid solution is formed with the small substitution of W6+ (x≤0.01). With the increase of x, the impurity phase BaWO4 occurrs and the grains become less homogeneous. Combined with the analysis of X-Ray Diffraction, the cation ordering degree on B-site increases in the sample of x=0.01, which leads to the decrease of the dielectric loss. However, the second phase BaWO4 inhibits the formation of the ordered structure with the reduction of sinterability. Due to the formation of BaWO4, the values of εr and τf of all samples decrease subsequently. The optimized microwave dielectric properties of Ba(Co1/3(Nb1-xW5x/6)2/3)O3 ceramics were obtained in the samples of x=0.01: εr=33.8, Q×f =110761 GHz, τf = -17 ppm/°C.

A new microwave dielectric ceramics based on the solid solution system between Ba(Ni1/3Nb2/3)O3 and Ba(Zn1/3Nb2/3)O3

1997 ◽  
Vol 12 (6) ◽  
pp. 1558-1562 ◽  
Author(s):  
Seo-Yong Cho ◽  
Hyuk-Joon Youn ◽  
Kug-Sun Hong ◽  
In-Tae Kim ◽  
Yoon-Ho Kim
Keyword(s):  
Solid Solution ◽  
Dielectric Properties ◽  
Pechini Method ◽  
Microwave Dielectric Properties ◽  
Processing Parameters ◽  
X Ray Diffraction ◽  
Solution System ◽  
Microwave Dielectric ◽  
Solid Solution System ◽  
Dielectric Ceramics

Microwave dielectric properties of the solid solution between Ba(Ni1/3Nb2/3)O3 and Ba(Zn1/3Nb2/3)O3 were investigated. Samples were prepared by the conventional mixed oxide method as well as the Pechini method. Sintered samples were analyzed using x-ray diffraction and scanning electron microscopy, and their microwave dielectric properties were measured by the post resonator method. The sample prepared by the Pechini method revealed excellent dielectric properties, i.e., permittivity of 35.6, quality factor of 5700 at 10 GHz, and very small temperature coefficient of resonant frequency. Order-disorder behavior of this solid solution system was found to depend on processing parameters. Variation in microwave dielectric properties was discussed in terms of the order-disorder behavior, chemical composition, mixture rule, etc.

Effect of Li2CO3-V2O5 on the Sintering and Microwave Dielectric Properties of 0.6Mg4Nb2O9-0.4SrTiO3 Composite Ceramics

2010 ◽  
Vol 663-665 ◽  
pp. 608-611
Author(s):  
Cui Jin Pei ◽  
Guo Guang Yao ◽  
Xiu Lao Tian ◽  
Hong Ma
Keyword(s):  
Dielectric Properties ◽  
Sintering Temperature ◽  
Microwave Dielectric Properties ◽  
Solid State Reaction Method ◽  
Composite Ceramics ◽  
X Ray Diffraction ◽  
Reaction Method ◽  
X Ray ◽  
Microwave Dielectric ◽  
Co Doped

The effects of Li2CO3-V2O5 (LV) co-doped on the sinterability, phase compositions and microwave dielectric properties of 0.6Mg4Nb2O9-0.4SrTiO3 composite ceramics have been investigated. All specimens were prepared by solid-state reaction method and sintered at 1050-1200oC for 5h. With an amount LV addition, the densification sintering temperature is significantly lowed from 1300oC to 1175oC. The non-stoichiometric compounds Sr(NbTi)O3+δ and Mg4(Nb1-xTix)2O9-δ were confirmed by X-ray diffraction and energy dispersive X-ray analysis. For the specimen with 1.5 wt% LV addition sintered at 1175oC for 5 h exhibited dielectric properties: εr=20.1, Q•f=10 240 GHz, τf =0.15 ppm/oC.

scholarly journals Sintering Behavior and Microwave Dielectric Properties of MgO-2B 2 O 3 - Xwt %H 3 BO 3 - Ywt %BCB Ceramics

2021 ◽  
Author(s):  
Haiquan WANG ◽  
Shixuan LI ◽  
Kangguo WANG ◽  
Huanfu ZHOU ◽  
Xiuli Chen
Keyword(s):  
Dielectric Properties ◽  
Bulk Density ◽  
Single Phase ◽  
Sintering Temperature ◽  
Microstructural Analysis ◽  
Microwave Dielectric Properties ◽  
Solid State Reaction Method ◽  
Sintering Behavior ◽  
X Ray Diffraction ◽  
Microwave Dielectric

Abstract The bulk density, sintering behavior and microwave dielectric properties of MgO-2B2O3 series ceramics synthesized by solid-state reaction method were systematically studied in this paper. X-ray diffraction and microstructural analysis revealed that the as-prepared MgO-2B2O3 ceramics possessed a single-phase structure with rod-like morphology. Through the investigation of the effects of different dosages of H3BO3 and BCB on bulk density, sintering behavior and microwave dielectric properties of MgO-2B2O3 ceramics, the optimum sintering temperature was obtained at an addition of 30wt%H3BO3 and 8wt%BCB and the sintering temperature was reduced to 825 oC. The addition of 40wt %H3BO3 and 4 wt%BCB increased the quality factor Q×f, permittivity εr and temperature coefficient of resonance frequency τf of MgO-2B2O3 to 44,306 GHz, 5.1 and -32 ppm/oC, respectively, meeting the criteria of low-temperature co-fired ceramics.

scholarly journals Effects of W6+ substitution on the microwave dielectric properties of Ce2Zr3(MoO4)9 ceramics

2019 ◽  
Vol 09 (06) ◽  
pp. 1950049
Author(s):  
Liang Shi ◽  
Cheng Liu ◽  
Huaiwu Zhang
Keyword(s):  
Dielectric Properties ◽  
Low Temperature ◽  
Microwave Dielectric Properties ◽  
Grain Morphology ◽  
Solid State Reaction Method ◽  
X Ray Diffraction ◽  
Conventional Solid State Reaction ◽  
Microwave Dielectric ◽  
Trigonal System ◽  
C Value

Low temperature sintered Ce2Zr3([Formula: see text][Formula: see text][Formula: see text] (marked as CZMW) ceramics were synthesized via the conventional solid-state reaction method. X-ray diffraction results showed that the CZMW ceramics belonged to a Trigonal system with R-3C space group, and without any impure phase formation. The experimental facts revealed that the density and grain morphology greatly affected the microwave dielectric properties. The samples sintered at 825∘C exhibited good microwave dielectric properties: [Formula: see text], [Formula: see text][Formula: see text]GHz (at 11.3[Formula: see text]GHz) and a satisfactory [Formula: see text] ([Formula: see text]1.5[Formula: see text]ppm/∘C) value. It is suggested that the CZMW ceramics are suitable for low-temperature co-fired ceramic (LTCC) applications in microwave devices.

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