Rutile TiO2 microwave dielectric ceramics prepared via cold sintering assisted two step sintering

Zhao, Enda; Hao, Jianyu; Xue, Xiaowei; Si, Mingming; Guo, Jing; Wang, Hong

doi:10.1016/j.jeurceramsoc.2020.12.009

Cited by 22 publications

(4 citation statements)

References 35 publications

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“…Microwave dielectric ceramics with high Q×f values (Q = 1/tanδ, and f is the resonant frequency) and excellent temperature stability are widely used to manufacture 5G antennas and filters [2][3][4][5]. In order to meet the requirements of device miniaturization, microwave dielectric ceramics having medium/high relative dielectric constants (ε r ) have been the focus of researches [6,7], including TiO 2 [8,9], Ba 6−3x Ln 8+2x Ti 18 O 54 (BLT, where Ln = rare earth element) [10,11], CaO-Li 2 O-Ln 2 O 3 -TiO 2 [12,13], Ca 1−x Ln 2x/3 TiO 3 (CLT) [14][15][16], lead-based perovskite [17,18], etc. In recent years, BLT with a tungsten-bronze structure and CLT with a perovskite structure have been extensively studied [19][20][21][22][23][24].…”

Section: Introduction mentioning

confidence: 99%

Structure, defects, and microwave dielectric properties of Al-doped and Al/Nd co-doped Ba4Nd9.33Ti18O54 ceramics

Guo

Luo

et al. 2022

J Adv Ceram

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Low-loss tungsten—bronze microwave dielectric ceramics are dielectric materials with potential application value for miniaturized dielectric filters and antennas in the fifth-generation (5G) communication technology. In this work, a novel Al/Nd co-doping method of Ba4Nd9.33Ti18O54 (BNT) ceramics with a chemical 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 a 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 = 16,480 GHz, and τf = +14.3 ppm/°C 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 structures and defects in microwave dielectric ceramics. It is shown that the improvement on Q×f values was originated from the decrease in the strength of the A-site cation vibration and the concentration of oxygen vacancies $$\text{V}_\text{O}^{^{ \cdot \cdot }}$$, demonstrating the effect and mechanism underlying for structural and defect modulation on the performance improvement of microwave dielectric ceramics.

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Section: Introduction mentioning

confidence: 99%

Structure, defects, and microwave dielectric properties of Al-doped and Al/Nd co-doped Ba4Nd9.33Ti18O54 ceramics

Guo

Luo

et al. 2022

J Adv Ceram

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“…Cold sintering process (CSP) is an innovation for the low‐temperature sintering that has developed rapidly in recent years 1–9 . It takes the advantage of mediate liquid phase with or without pressure to facilitate the densification below 300°C and now has been successfully applied in a wide variety of materials such as BaTiO 3 , SiO 2 , Al 2 O 3 and TiO 2 10–14 . Cold sintering is a complex process, involving liquid phase diffusion, arrangement of particles and interaction between liquid phase and particles 2,15–17 .…”

Section: Introductionmentioning

confidence: 99%

“…[1][2][3][4][5][6][7][8][9] It takes the advantage of mediate liquid phase with or without pressure to facilitate the densification below 300 • C and now has been successfully applied in a wide variety of materials such as BaTiO 3 , SiO 2 , Al 2 O 3 and TiO 2 . [10][11][12][13][14] Cold sintering is a complex process, involving liquid phase diffusion, arrangement of particles and interaction between liquid phase and particles. 2,[15][16][17] Up to now, several cold sintering mechanisms have been reported, and the most accepted mechanisms include the "dissolution-precipitation" process and plastic deformation process.…”

Section: Introductionmentioning

confidence: 99%

The effects of cold sintering parameters on the densification of Na₂WO₄ ceramics using Na₂WO₄·2H₂O dry powders

Hao

Guo

et al. 2022

J Am Ceram Soc.

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Cold sintering process (CSP) combines transient liquid phase and/or external pressure to assist the densification of ceramics, the sintering mechanism of which is typically dominated by the “dissolution–precipitation” process. In this work, Na2WO4·2H2O dry powders without liquid water have been used as the “liquid phase” to realize the densification of Na2WO4 ceramics. The effects of sintering parameters on the CSP of Na2WO4 ceramics using Na2WO4·2H2O dry powders are systematically studied, including sintering temperature, external pressure, sintering process time and the amount of Na2WO4·2H2O phase. It is found that the “liquid phase,” that is, Na2WO4·2H2O is the key factor for controlling the CSP of Na2WO4 ceramics, and Na2WO4·2H2O hydrate shows an advantage of homogeneous dispersion of liquid water. The sintering temperature affects the densification mechanism involved with plastic deformation and the “dissolution–precipitation,” external pressure accelerates the densification process, and enough sintering process time ensures the completion of CSP. Finally, the optimum cold sintering parameters of Na2WO4 ceramics by Na2WO4·2H2O powders are obtained at 150°C and 240 MPa for 60 min with a pretreatment at 150°C for 30 min.

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“…The enhancement of the εr could be related to the Zr substitution at the Ti la ice site [54]. This increase may also be a ributed to the complex process of grain growth and densification of the ceramic [55,56]. Another crucial factor contributing to the enhancement of εr is the ionic polarizability.…”

Section: Resultsmentioning

confidence: 99%

Origin of Temperature Coefficient of Resonance Frequency in Rutile Ti1−xZrxO2 Microwave Ceramics

Khan,

Muhammad

et al. 2024

Ceramics

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In this study, we report the effect of Zr4+ doping on the optical energy gap and microwave dielectric properties of rutile TiO2. Rietveld analysis explicitly confirmed that Zr4+ occupies the octahedral site, forming a single-phase tetragonal structure below the solubility limit (x < 0.10). Notably, at x = 0.025, a significant enhancement in Q × fo was observed. This enhancement was attributed to the reduction in dielectric loss, associated with a decrease in oxygen vacancies and a lower concentration of Ti3+ paramagnetic centers. This conclusion was supported by Raman and electron paramagnetic resonance spectroscopy, respectively. The origin of high τf in rutile Ti1−xZrxO2 is explained on the basis of the octahedral distortion/tetragonality ratio, covalency, and bond strength.

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Rutile TiO2 microwave dielectric ceramics prepared via cold sintering assisted two step sintering

Cited by 22 publications

References 35 publications

Structure, defects, and microwave dielectric properties of Al-doped and Al/Nd co-doped Ba4Nd9.33Ti18O54 ceramics

Structure, defects, and microwave dielectric properties of Al-doped and Al/Nd co-doped Ba4Nd9.33Ti18O54 ceramics

The effects of cold sintering parameters on the densification of Na₂WO₄ ceramics using Na₂WO₄·2H₂O dry powders

Origin of Temperature Coefficient of Resonance Frequency in Rutile Ti1−xZrxO2 Microwave Ceramics

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Rutile TiO2 microwave dielectric ceramics prepared via cold sintering assisted two step sintering

Cited by 22 publications

References 35 publications

Structure, defects, and microwave dielectric properties of Al-doped and Al/Nd co-doped Ba4Nd9.33Ti18O54 ceramics

Structure, defects, and microwave dielectric properties of Al-doped and Al/Nd co-doped Ba4Nd9.33Ti18O54 ceramics

The effects of cold sintering parameters on the densification of Na2WO4 ceramics using Na2WO4·2H2O dry powders

Origin of Temperature Coefficient of Resonance Frequency in Rutile Ti1−xZrxO2 Microwave Ceramics

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The effects of cold sintering parameters on the densification of Na₂WO₄ ceramics using Na₂WO₄·2H₂O dry powders