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.

Effects of Sintering Temperatures on Microwave Properties of Mg4Nb2O9 Ceramics by the Solid-State Process

2012 ◽  
Vol 499 ◽  
pp. 178-182
Author(s):  
Yi Shan Jiang ◽  
Ying Zi Wang ◽  
Ya Ming Chen ◽  
Yun Long Yue ◽  
Hai Tao Wu
Keyword(s):  
Dielectric Properties ◽  
Solid State ◽  
Sintering Temperature ◽  
Microwave Dielectric Properties ◽  
Microwave Dielectric Ceramics ◽  
Solid State Method ◽  
Microwave Dielectric ◽  
State Process ◽  
Density Values ◽  
Dielectric Ceramics

Microwave dielectric ceramics of Mg4Nb2O9were prepared by the solid-state method and their microwave dielectric properties and microstructure were investigated in this study. The sintering ability and microwave dielectric properties of Mg4Nb2O9ceramics were studied under various sintering temperatures ranging from 1200°C to 1350°C. As the sintering temperature increased from 1200°C to 1350°C, the density values, the εr values and the Q·ƒ values increased and saturated at 1350°C.The ƒ values were ranged from -48.7 to -57.8 ppm/°C. Due to the increased density and appropriate grain growth the Mg4Nb2O9ceramics sintered at 1350°C had the excellent microwave dielectric properties of εr=12.3, Q·ƒ =108,000GHz and ƒ=-55.3ppm/°C.

Preparation and Dielectric Properties of BaO-Sm2O3-4TiO2 Microwave Ceramics with B2O3 and CuO Addition Sintered in Low Temperature

2008 ◽  
Vol 368-372 ◽  
pp. 173-175 ◽  
Author(s):  
Wei Liang Liu ◽  
Chun Bao Tang ◽  
Jun Tan ◽  
Du Song Mao ◽  
Jin Gang Tan
Keyword(s):  
Dielectric Properties ◽  
Sintering Temperature ◽  
Tungsten Bronze ◽  
Microwave Dielectric Properties ◽  
Microwave Dielectric Ceramics ◽  
Microwave Ceramics ◽  
Sintering Aid ◽  
Microwave Dielectric ◽  
Bst Ceramics ◽  
Dielectric Ceramics

BaCu(B2O5) (BCB) powder was prepared using BaO,CuO and B2O3 as the main materials. Microwave dielectric ceramics of tungsten–bronze-type BaSm2Ti4O12 (BST) were prepared by doping BCB as the sintering aid. The amount of BCB was varied from 1.0 to 10.0wt.%. The microstructure and dielectric properties of BST were investigated. The sintering temperature of BST ceramics with 6.0wt.% BCB addition can be effectively reduced to 900 oC, about 450 oC lower than that of pure BST ceramics. Good microwave dielectric properties of εr = 62.38, Q×f = 4573 GHz and τf = -27.65 ppm/ oC were achieved.

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.

Structure and Microwave Dielectric Properties of (Ca0.9375Sr0.0625)0.25 (Li0.5Sm0.5)0.75TiO3 Ceramics with B2O3-CuO Sintering Aids

2011 ◽  
Vol 284-286 ◽  
pp. 1442-1446
Author(s):  
Yue Ming Li ◽  
Zong Yang Shen ◽  
Zhu Mei Wang ◽  
Hua Zhang ◽  
Yan Hong ◽  
...  
Keyword(s):  
Crystal Structure ◽  
Dielectric Properties ◽  
Sintering Temperature ◽  
Microwave Dielectric Properties ◽  
Microwave Dielectric Ceramics ◽  
Sintering Aids ◽  
Oxide Mixture ◽  
High Permittivity ◽  
Microwave Dielectric ◽  
Dielectric Ceramics

The B2O3-CuO oxide mixture (abbreviated as BC) was selected to lower the sintering temperature of (Ca0.9375Sr0.0625)0.25(Li0.5Sm0.5)0.75TiO3 (abbreviated as CSLST) microwave dielectric ceramics by solid sate reaction technique. The effects of BC doping amounts on the crystal structure, microstructure and microwave dielectric properties of the ceramics were investigated. For the ceramic sample with the composition of CSLST + 5 wt% BC, its sintering temperature was reduced to 1000 °C as compared to 1200 °C for pure CSLST. In addition to the obtained good microwave dielectric properties as follows: εr = 80.4, Q×f = 1380 GHz, τf = -32.89 ×10-6/°C, this ceramic was a desirable high-permittivity microwave dielectric candidate for low-temperature cofired ceramic (LTCC) applications.

Low Temperature Sintering of (Ca0.9375Sr0.0625)0.25(Li0.5Sm0.5)0.75TiO3 Microwave Dielectric Ceramics

2010 ◽  
Vol 663-665 ◽  
pp. 1028-1031
Author(s):  
Yue Ming Li ◽  
Hua Zhang ◽  
Zhu Mei Wang ◽  
Yan Hong ◽  
Zong Yang Shen
Keyword(s):  
Dielectric Properties ◽  
Low Temperature ◽  
Sintering Temperature ◽  
Microwave Dielectric Properties ◽  
Sintering Behavior ◽  
Low Temperature Sintering ◽  
Microwave Dielectric Ceramics ◽  
Microwave Dielectric ◽  
Dielectric Ceramics

The sintering behavior and microwave dielectric properties of the (Ca0.9375Sr0.0625)0.25(Li0.5Sm0.5)0.75TiO3 (CSLST) ceramics doped with different amounts of Li2O-B2O3-SiO2-CaO-Al2O3 (LBSCA) glass were investigated. The sintering temperature of the CSLST ceramics can be effectively reduced over 200oC due to the addition of LBSCA glass. For the 5 wt% LBSCA-doped CSLST ceramics, which are sintered at only 1000 oC for 5 h, show optimum microwave dielectric properties as follows: εr=84.74, Qf=2446 GHz and τf=-12.48 ppm/oC.

Microwave Dielectric Properties of Ca1-x(Li1/2Sm1/2)xTiO3 Ceramics

2010 ◽  
Vol 105-106 ◽  
pp. 238-241 ◽  
Author(s):  
Yue Ming Li ◽  
Ting Ting Song ◽  
Fei Hu ◽  
Run Hua Liao ◽  
Bin Zhang
Keyword(s):  
Crystal Structure ◽  
Dielectric Properties ◽  
Microwave Dielectric Properties ◽  
Microwave Dielectric Ceramics ◽  
Fabrication Technique ◽  
Microwave Dielectric ◽  
Polarizability Effect ◽  
Orthorhombic Perovskite ◽  
Dielectric Ceramics ◽  
A Site

Ca1-x(Li1/2Sm1/2)xTiO3 microwave dielectric ceramics in the x range of 0.70 ~ 0.80 were prepared by conventional ceramics fabrication technique. The crystal structure, microstructure and microwave dielectric properties were investigated. The results showed that a single orthorhombic perovskite structure formed within this x range, and the substitution of (Li1/2Sm1/2)2+ ion for Ca2+ ion in A-site has a significant influence on the microwave dielectric properties of the ceramics. With the increase of substitution of (Li1/2Sm1/2)2+ ion with 0.75, the temperature coefficient of resonant frequency τf reaches zero, and it could be attributed that the Sm and Li have a polarizability effect according to its microstructure. The Ca0.25(Li1/2Sm1/2)0.75TiO3 ceramic had a good performance with microwave dielectric properties of τf = 0 ppm/°C, εr = 105.83, and Qf = 3170 GHz.

scholarly journals The latest process and challenges of microwave dielectric ceramics based on pseudo phase diagrams

2021 ◽  
Vol 10 (5) ◽  
pp. 885-932
Author(s):  
Hongcheng Yang ◽  
Shuren Zhang ◽  
Hongyu Yang ◽  
Qingyu Wen ◽  
Qiu Yang ◽  
...  
Keyword(s):  
Dielectric Material ◽  
Synthesis Method ◽  
Microwave Dielectric Properties ◽  
Dielectric Materials ◽  
Microwave Dielectric Ceramics ◽  
Structure Property ◽  
Extrinsic Factors ◽  
Intrinsic Polarization ◽  
Microwave Dielectric ◽  
Dielectric Ceramics

AbstractThe explosive process of 5G communication evokes the urgent demand of miniaturized and integrated dielectric ceramics filter. It is a pressing need to advance the development of dielectric ceramics utilization of emerging technology to design new materials and understand the polarization mechanism. This review provides the summary of the study of microwave dielectric ceramics (MWDCs) sintered higher than 1000 from 2010 up to now, °C with the purpose of taking a broad and historical view of these ceramics and illustrating research directions. To date, researchers endeavor to explain the structure-property relationship of ceramics with multitude of approaches and design a new formula or strategy to obtain excellent microwave dielectric properties. There are variety of factors that impact the permittivity, dielectric loss, and temperature stability of dielectric materials, covering intrinsic and extrinsic factors. Many of these factors are often intertwined, which can complicate new dielectric material discovery and the mechanism investigation. Because of the various ceramics systems, pseudo phase diagram was used to classify the dielectric materials based on the composition. In this review, the ceramics were firstly divided into ternary systems, and then brief description of the experimental probes and complementary theoretical methods that have been used to discern the intrinsic polarization mechanisms and the origin of intrinsic loss was mentioned. Finally, some perspectives on the future outlook for high-temperature MWDCs were offered based on the synthesis method, characterization techniques, and significant theory developments.

scholarly journals Compositional modulation in ZnGa2O4 via Zn2+/Ge4+ co-doping to simultaneously lower sintering temperature and improve microwave dielectric properties

2021 ◽  
Author(s):  
Ying Xiong ◽  
Hongyuan Xie ◽  
Zhenggang Rao ◽  
Laijun Liu ◽  
Zhengfeng Wang ◽  
...  
Keyword(s):  
Dielectric Properties ◽  
Quality Factor ◽  
Spinel Structure ◽  
High Speed ◽  
Sintering Temperature ◽  
Microwave Dielectric Properties ◽  
Signal Propagation ◽  
Solid State Method ◽  
Co Doping ◽  
Microwave Dielectric

AbstractAB2O4-type spinels with low relative permittivity (εr) and high quality factor (Q × f) are crucial to high-speed signal propagation systems. In this work, Zn2+/Ge4+ co-doping to substitute Ga3+ in ZnGa2O4 was designed to lower the sintering temperature and adjust the thermal stability of resonance frequency simultaneously. Zn1+xGa2−2xGexO4 (0.1 ⩽ x ⩽ 0.5) ceramics were synthesised by the conventional solid-state method. Zn2+/Ge4+ co-substitution induced minimal variation in the macroscopical spinel structure, which effectively lowered the sintering temperature from 1385 to 1250 °C. All compositions crystallized in a normal spinel structure and exhibited dense microstructures and excellent microwave dielectric properties. The compositional dependent quality factor was related to the microstructural variation, being confirmed by Raman features. A composition with x = 0.3 shows the best dielectric properties with εr ≈ 10.09, Q × f ≈ 112,700 THz, and τf ≈ −75.6 ppm/°C. The negative τf value was further adjusted to be near-zero through the formation of composite ceramics with TiO2.

Novel low temperature sintered Li4Ti5O12 microwave dielectric ceramics with MoO2 addition

2016 ◽  
Vol 30 (23) ◽  
pp. 1650287
Author(s):  
Cheng Liu ◽  
Huaiwu Zhang ◽  
Hua Su ◽  
Lichuan Jin ◽  
Jie Li ◽  
...  
Keyword(s):  
Dielectric Properties ◽  
Crystal Morphology ◽  
Microwave Dielectric Properties ◽  
Microwave Dielectric Ceramics ◽  
Reaction Route ◽  
Microwave Dielectric ◽  
Suitable Amount ◽  
Solid State Reaction Route ◽  
Dielectric Ceramics ◽  
Pure Phases

Li4Ti5O[Formula: see text] ceramics with different amount of MoO2 addition were densified at 850[Formula: see text]C via a solid-state reaction route. Pure phases and dense crystal morphology were obtained. Our experimental results indicated that the [Formula: see text] value of the Li4Ti5O[Formula: see text] ceramic can be adjusted to near zero via adopting suitable amount of MoO2 addition. Among all the modified Li4Ti5O[Formula: see text] specimens, the sample with 4 wt.% of MoO2 addition (marked as LM4 in this paper) possessed good microwave dielectric properties: [Formula: see text], [Formula: see text] GHz (7.99 GHz), [Formula: see text] ppm/[Formula: see text]C. It is suggested that the MoO2 modified Li4Ti5O[Formula: see text] ceramics are suitable candidates for LTCC applications in microwave devices.

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