scholarly journals Phase evolution and microwave dielectric properties of A5M5O17-type ceramics

2017 ◽  
Vol 35 (2) ◽  
pp. 362-367
Author(s):  
Murad Ali ◽  
Yaseen Iqbal ◽  
Raz Muhammad
Keyword(s):  
Dielectric Properties ◽  
Solid State ◽  
Rare Earths ◽  
Relative Permittivity ◽  
Microwave Dielectric Properties ◽  
Phase Evolution ◽  
Ionic Radii ◽  
Microwave Dielectric ◽  
Solid State Sintering ◽  
Quality Factor Q

Abstract A number of A5M5O17 (A = Na, Ca, Sr, La, Nd, Sm, Gd, Dy, Yb; B = Ti, Nb, Ta) type compounds were prepared by a solid-state sintering route and characterized in terms of structure, microstructure and microwave dielectric properties. The compatibility of rare earths with mixed niobate/tantalate and titanate phases was investigated. The larger ionic radii mismatch resulted in the formation of pyrochlore and/or mixed phases while in other cases, pure A5M5O17 phase was formed. The samples exhibited relative permittivity in the range of 35 to 82, quality factor (Q × fo) = 897 GHz to 11946 GHz and temperature coefficient of resonance frequency (τf) = -120 ppm/°C to 318 ppm/°C.

Microstructure and Microwave Dielectric Properties of BaTi4O9 Ceramics Derived from a Sol-Gel Precursor

2011 ◽  
Vol 326 ◽  
pp. 127-130
Author(s):  
Xian Li Huang ◽  
Fu Ping Wang ◽  
Ying Song
Keyword(s):  
Dielectric Constant ◽  
Dielectric Properties ◽  
Dielectric Loss ◽  
Sol Gel ◽  
Microwave Dielectric Properties ◽  
Sintering Process ◽  
Temperature Coefficients ◽  
Microwave Dielectric ◽  
Ceramic Samples ◽  
Quality Factor Q

In the present work, the microstructure and microwave dielectric properties of BaTi4O9 ceramics derived from a sol-gel precursor were presented. Density measuring results demonstrated that the largest densities of ceramic sample about 96.7% could be reached by virtue of a cool iso-static press and a sintering process at at 1300 °C for 6 hours. The dielectric constant (εr), quality factor (Q×f) and the temperature coefficients (τf) of the BaTi4O9 ceramic samples were 36.65, 28000 GHz, +20.2 ppm/°C, respectively. XRD, SEM and XPS were used to characterize the microstructure of the ceramics samples. Substantial Ti3+ was proposed to be the cause of dielectric loss.

scholarly journals Structural, optical and microwave dielectric properties of Ba(Ti1−xSnx)4O9, 0 ≤ x ≤ 0.7 ceramics

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Asad Ali ◽  
Sarir Uddin ◽  
Madan Lal ◽  
Abid Zaman ◽  
Zafar Iqbal ◽  
...  
Keyword(s):  
Dielectric Properties ◽  
Microwave Dielectric Properties ◽  
Orthorhombic Symmetry ◽  
X Ray Diffraction ◽  
Low Dielectric ◽  
Microwave Dielectric ◽  
Ceramic Samples ◽  
Red Color ◽  
High Dielectric ◽  
Quality Factor Q

AbstractSn-doped BaTi4O9 (BT4) dielectric ceramics were prepared by a mixed oxide route. Preliminary X-ray diffraction (XRD) structural study shows that the ceramic samples have orthorhombic symmetry with space group (Pnmm). Scanning electron microscopy (SEM) shows that the grain size of the samples decreases with an increase in Sn4+ content. The presence of the metal oxide efficient group was revealed by Fourier transform infrared (FTIR) spectroscopy. The photoluminescence spectra of the ceramic samples reported red color ~ 603, 604, 606.5 and 605 nm with excitation energy ~ 2.06, 2.05, 2.04 and 2.05 eV for Sn4+ content with x = 0.0, 0.3, 0.5, and 0.7, respectively. The microwave dielectric properties of these ceramic samples were investigated by an impedance analyzer. The excellent microwave dielectric properties i.e. high dielectric constant (εr = 57.29), high-quality factor (Qf = 11,852), or low-dielectric loss (3.007) has been observed.

Dielectric Properties of a New Ceramic System (1-x)(Mg0.95Zn0.05)2TiO4-x(Ca0.8Sr0.2)TiO3 at Microwave Frequencies

2020 ◽  
Vol 830 ◽  
pp. 37-42
Author(s):  
Shih Sheng Liu ◽  
Shiuan Ho Chang ◽  
Yuan Bin Chen
Keyword(s):  
Dielectric Properties ◽  
Microwave Dielectric Properties ◽  
Second Phase ◽  
X Ray Diffraction ◽  
Low Loss ◽  
Microwave Frequencies ◽  
Solid State Route ◽  
Microwave Dielectric ◽  
System 1 ◽  
Quality Factor Q

The microwave dielectric properties and microstructures of the (1-x)(Mg0.95Zn0.05)2TiO4-x (Ca0.8Sr0.2)TiO3 ceramics prepared using the conventional solid-state route were investigated. The structure and microstructure were analyzed by X-ray diffraction (XRD) and scanning electron microscopy (SEM), respectively. Ilmenite-structured (Mg0.95Zn0.05)TiO3 was detected as a second phase. The coexistence of the second phase, however, did not degrade the dielectric properties of the specimen because the phases were compatible. At x = 0.07, a dielectric constant (εr) of ~17.86, a quality factor (Q×f) value of ~ Q×f~133,600 Hz (at 10 GHz), and a temperature coefficient of resonant frequency (τf) of ~ –5ppm/°Cwere obtained for 0.93(Mg0.95Zn0.05)2TiO4-0.07(Ca0.8Sr0.2)TiO3 ceramic sintered at 1240°C for 4 hr. The dielectric is proposed as a candidate material for low-loss microwave and millimeter wave applications.

Low-Temperature Sintering and Microwave Dielectric Properties of CaWO4-Mg2SiO4 Ceramics

2014 ◽  
Vol 933 ◽  
pp. 12-16 ◽  
Author(s):  
Chung Long Pan ◽  
Ping Cheng Chen ◽  
Tsu Chung Tan ◽  
Wei Cheng Lin ◽  
Chun Hsu Shen ◽  
...  
Keyword(s):  
Dielectric Properties ◽  
Solid State ◽  
Liquid Phase ◽  
Sintering Temperature ◽  
Microwave Dielectric Properties ◽  
Liquid Phase Sintering ◽  
Low Temperature Sintering ◽  
Sintering Aids ◽  
Sintering Aid ◽  
Microwave Dielectric

The effect of V2O5addition on the microstructures and the microwave dielectric properties of 0.9CaWO4-0.1Mg2SiO4(9CWMS) ceramics prepared by conventional solid-state routes have been investigated. The V2O5were selected as liquid phase sintering aids to lower the sintering temperature of 9CWMS ceramics. A small amount of V2O5(0.25~1 wt%) were used for sintering aid and led to high densification at 1050°C. The dielectric properties of 9CWMS ceramics with V2O5additions are strongly dependent on the densification, the microstructure. As the amount of V2O5additives increased from 0.25 to 1.0 wt%, the dielectric constantsεrdecreased following the trend with density. The quality valuesQdecreased with the increase of V2O5amount for all sintering temperatures. The 0.25 wt% V2O5-doped 0.9CaWO4-0.1Mg2SiO4ceramicssintered at 1080°C for 2 h had the optimum dielectric properties: εr= 5.7;Q×f= 73000 (at 14 GHz).

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