High‐Dielectric‐Constant and Low‐Loss Microwave Dielectric in the (1−x)Nd(Zn1/2Ti1/2)O3–xSrTiO3 System with a Zero Temperature Coefficient of Resonant Frequency

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Composite ceramics in a solid solution of (Mg1−x Mnx)2TiO4 (x=0.02–0.1) have been prepared by the mixed oxide route. Formation of the solid solution was confirmed by the X‐ray diffraction, the EDX analysis, and the measured lattice parameters, which varied linearly from Mg2TiO4 (a=b=c=8.4410 Å) to (Mg0.9 Mn0.1)2TiO4 (a=b=c=8.4445 Å). The XRD analysis also confirmed the co‐existence of a cubic‐structured (Mg1−xMnx)2TiO4 and an ilmenite‐structured second phase (Mg1−xMnx)TiO3. The composition expected to have a maximum Q×f (276 200 GHz at 10.5 GHz) is (Mg0.95Mn0.05)2TiO4 with ɛr∼15.69 and τf∼−52.6 ppm/°C. The existence of the second phase, however, would lead to no significant variation in the dielectric properties of the specimen because it possesses compatible properties compared with that of the main phase.

Section: Introductionmentioning

confidence: 99%

Low‐Loss Microwave Dielectric Ceramics Using (Mg₁₋_xMn_x)₂TiO₄ (x=0.02–0.1) Solid Solution

Huang¹,

Chen²

2009

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“…It implies that overheating the specimen may lead to an over‐grown TiO 2 grain, which would result in an abnormal grain growth. Moreover, by taking the apparent size difference in grains into consideration, a mixture of two phases along with an appropriate ratio could effectively hold back the abnormal grain growth as a result of rapid grain growth 20,21 . This explained why the average grain size of TiO 2 in our experiment was smaller than that reported by Lei et al 10 under similar conditions.…”

Section: Resultsmentioning

confidence: 44%

Low Dielectric Loss Ceramics in the ZnAl₂O₄–TiO₂ System as a τ_f Compensator

Huang

Yang

Huang

2009

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The microstructure and microwave dielectric properties of a (1Àx)ZnAl 2 O 4 -xTiO 2 ceramic system prepared by the mixed oxide route have been investigated. The phases of ZnAl 2 O 4 and TiO 2 co-exist with each other and form a two-phase system, which is confirmed by the X-ray diffraction patterns and the energy dispersive X-ray spectrometer analysis. The microwave dielectric properties of the specimens are strongly related to the sintering temperature, the density, and the mole ratio of ZnAl 2 O 4 /TiO 2 . The sintering temperature of the specimen can be effectively lowered by increasing the TiO 2 content. The Q u Â f values of the ceramics can be significantly boosted by adding an appropriate amount of TiO 2 and by sintering at a suitable temperature. Consequently, a very high Q u Â f of 277 000 GHz associated with an e r of 25.2 and a large resonant frequency (s f ) of 177 ppm/1C are obtained using 0.5ZnAl 2 O 4 -0.5TiO 2 ceramics at 13901C/4 h. These unique properties can be utilized as a s f compensator for dielectrics that would require extremely low loss. The MgTiO 3 and Mg 4 Nb 2 O 9 having negative s f were mixed with 0.5ZnAl 2 O 4 -0.5TiO 2 ceramics to achieve dielectrics with a low e r , a high Q u Â f, and a nearly-zero s f . In addition, a circle dual-mode microstrip bandpass filter is designed and fabricated using the proposed dielectric to study its performance.

“…M iniaturization of dielectric resonators for volume efficiency in modern microwave telecommunication technology such as 3G, global positioning systems and wireless local area networks is a primary requirement. These dielectric resonators must satisfy three main criteria: a high dielectric constant for size miniaturization, a low dielectric loss for better selectivity, and a near‐zero temperature coefficient of resonant frequency (τ f ) for stable frequency stability 1 . However, high‐dielectric‐constant materials exhibit high dielectric loss (low Q × f value), whereas low‐loss ceramics are usually accompanied by a low ɛ r value.…”

Section: Introductionmentioning

confidence: 99%

“…However, high‐dielectric‐constant materials exhibit high dielectric loss (low Q × f value), whereas low‐loss ceramics are usually accompanied by a low ɛ r value. Achieving all three requirements in one material is a formidable problem and therefore a number of materials have been proposed 1–8 …”

Section: Introductionmentioning

confidence: 99%

Structure, Dielectric Properties, and Applications of CaTiO3-Modified Ca4MgNb2TiO12 Ceramics at Microwave Frequency

Huang

Tseng

2011

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High‐dielectric‐constant and low‐loss ceramics in the (1−x)Ca4MgNb2TiO12–xCaTiO3 system have been prepared by the conventional solid‐state route. The forming of complete (1−x)Ca4MgNb2TiO12–xCaTiO3 solid solutions were confirmed by the X‐ray diffraction pattern analysis and the measured lattice parameters, which linearly varied from a=5.5478 Å, b=7.7710 Å, and c=5.4543 Å for x=0.1 to a=5.4718 Å, b=7.6799 Å, and c=5.4262 Å for x=0.9. By increasing x, not only could the τf of the ceramics be turned to a near‐zero value (∼−6.9 ppm/°C) at x=0.3, a substantial Q×f (∼20 200 GHz) and ɛr (∼43.88) could also be achieved simultaneously.