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Journal ArticleDOI

Microwave dielectric properties of (Ba, Sr)(Zn1/3Ta2/3)O3 dielectric resonators

15 Apr 1999-Materials Chemistry and Physics (Elsevier)-Vol. 58, Iss: 3, pp 276-279
TL;DR: In this paper, the dielectric properties of these compounds are related to the structural distortion due to octahedra tilting, and an anomaly exists for the composition Ba 0.5Sr0.5(Zn 1/3Ta2/3)O3.
About: This article is published in Materials Chemistry and Physics.The article was published on 1999-04-15. It has received 10 citations till now. The article focuses on the topics: Dielectric resonator & Dielectric.
Citations
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Journal ArticleDOI
Fei Zhao1, Zhenxing Yue1, Yingchun Zhang1, Zhilun Gui1, Longtu Li1 
TL;DR: In this paper, the microwave dielectric properties of Ca[Ti 1− x (Mg 1/3 Nb 2/3 ) x ]O 3 (x ǫ = 0.40 to 0.70) were studied as a function of composition and sintering temperature.
Abstract: Microwave dielectric ceramics of Ca[Ti 1− x (Mg 1/3 Nb 2/3 ) x ]O 3 ( x = 0.40–0.70) were prepared by solid-state reaction method. The microwave dielectric properties, such as dielectric constants, Q × f values and τ f (temperature coefficient of resonant frequency) were studied as a function of composition and sintering temperature. In all the studied composition range, the sintered ceramics have orthorhombic perovskite structure in which the lattice parameters increase with increasing x . The substitution of Mg and Nb for Ti promotes the grain growth. With x increasing from 0.40 to 0.70, the dielectric constant decreases from 62.97 to 41.56, Q × f value increases from 12,213 to 29,428 GHz, and τ f decreases from 92.6 to −12.6 ppm/°C. A near-zero τ f was achieved at x = 0.65 with dielectric constant of 44.24 and Q × f value of 28,340 GHz. The change of dielectric constant and τ f with x is related to the variation of the tolerance factor, which influences the tilting of oxygen octahedra in perovskite structure.

38 citations

Journal ArticleDOI
TL;DR: In this paper, the authors reported the highest observed values of Qu×f=103.730 GHz, and ǫ r=261 for the ZnNb2O6-sintered ceramics.
Abstract: (Ni1−xZnx)Nb2O6, 0≤x≤10, ceramics with >97% density were prepared by a conventional solid-state reaction, followed by sintering at 1200°–1300°C (depending on the value of x) The XRD patterns of the sintered samples (0≤x≤10) revealed single-phase formation with a columbite (Pbcn) structure The unit cell volume slightly increased with increasing Zn content (x) All the compositions showed high electrical resistivity (ρdc=16±03 × 1011Ω·cm) The microwave (4–5 GHz) dielectric properties of (Ni1−xZnx)Nb2O6 ceramics exhibited a significant dependence on the Zn content and to some extent on the morphology of the grains As x was increased from 0 to 1, the average grain size monotonically increased from 76 to 212 μm and the microwave dielectric constant (ɛ′r) increased from 236 to 261, while the quality factors (Qu×f) increased from 18 900 to 103 730 GHz and the temperature coefficient of resonant frequency (τf) increased from −62 to −73 ppm/°C In the present work, we report the highest observed values of Qu×f=103 730 GHz, and ɛ′r=261 for the ZnNb2O6-sintered ceramics

26 citations

Journal ArticleDOI
TL;DR: In this article, the microwave dielectric properties of the Ba2Ca1−xSrxWO6 (x=0-1) single-phase ceramics with double perovskite structures were obtained.
Abstract: Ba2Ca1−xSrxWO6 (x=0–1) microwave dielectric ceramics have been prepared using the two-step solid-state reaction method. The substitution of Sr2+ for Sr2+ can effectively lower the densification temperature of the ceramics from 1500° to 1200°C. Single-phase ceramics with double perovskite structures were obtained, and structural transitions occurred in Ba2Ca1−xSrxWO6 via the phase sequence: cubic→rhombohedral→monoclinic with an increase of x. The microwave dielectric properties of the Ba2Ca1−xSrxWO6 ceramics can be effectively tuned by tailoring x. The dielectric constant (ɛr) remains almost unvaried, the quality factor (Q × f) decreases monotonically, and the temperature coefficient of resonant frequency (τf) changes in sign with the increase of x. A good combination of the microwave dielectric properties was obtained for Ba2Ca0.975Sr0.025WO6 sintered at 1250°C: ɛr=23.9, Q × f=80 200 GHz, and τf=+18 ppm/°C.

20 citations

Journal ArticleDOI
TL;DR: In this article, the effect of the tilting of octahedra on polar phonon modes of lattice vibration was investigated, which contributes a major part to the dielectric polarization in the crystal.
Abstract: The aim of this work is to understand the effect of the tilting of octahedra on polar phonon modes of lattice vibration, which contributes a major part to the dielectric polarization in the crystal. The tolerance factor, which is a measure of the packing of ions in the perovskite unit cell, determines the tilting of oxygen octahedra in the perovskite materials. In this work we have discussed the variation of polar phonon frequencies with respect to the tolerance factor in the composition (Ba(1−x)Srx)(Zn1/3Ta2/3)O3 with x=0.0,0.3,0.5,0.7,1.0. The dielectric properties measured at the microwave frequency range are also highlighted to support the ideas proposed in this paper.

15 citations

Journal ArticleDOI
TL;DR: In this paper, Ba(Zn 1/3 Ta 2/3 )O 3 -based perovskite compounds, including Ba 1/6 Co 1/9 Nb 2/9 Sb 2 /9, were prepared and characterized, and the results showed no second phase formation shown in the XRD patterns.

13 citations

References
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Journal ArticleDOI
TL;DR: The effective ionic radii of Shannon & Prewitt [Acta Cryst. (1969), B25, 925-945] are revised to include more unusual oxidation states and coordinations as mentioned in this paper.
Abstract: The effective ionic radii of Shannon & Prewitt [Acta Cryst. (1969), B25, 925-945] are revised to include more unusual oxidation states and coordinations. Revisions are based on new structural data, empirical bond strength-bond length relationships, and plots of (1) radii vs volume, (2) radii vs coordination number, and (3) radii vs oxidation state. Factors which affect radii additivity are polyhedral distortion, partial occupancy of cation sites, covalence, and metallic character. Mean Nb5+-O and Mo6+-O octahedral distances are linearly dependent on distortion. A decrease in cation occupancy increases mean Li+-O, Na+-O, and Ag+-O distances in a predictable manner. Covalence strongly shortens Fe2+-X, Co2+-X, Ni2+-X, Mn2+-X, Cu+-X, Ag+-X, and M-H- bonds as the electronegativity of X or M decreases. Smaller effects are seen for Zn2+-X, Cd2+-X, In2+-X, pb2+-X, and TI+-X. Bonds with delocalized electrons and therefore metallic character, e.g. Sm-S, V-S, and Re-O, are significantly shorter than similar bonds with localized electrons.

51,997 citations

Journal ArticleDOI
TL;DR: In this article, a novel technique for the measurement of dielectric and magnetic properties of a homogeneous isotropic medium in the range of approximately 3 to 100 kmc is described.
Abstract: A novel technique for the measurement of dielectric and magnetic properties of a homogeneous isotropic medium in the range of approximately 3 to 100 kmc is described. An accuracy of /l.chemc/ 1 per cent is possible in the determination of permittivity or permeability in those cases where the loss tangent is sulliciently small. The measuring structure is a resonator made up of a right circular cyndrical dielectric rod placed between two parallel conducting plates. For measurement of permittivity two or more resonant TE/sub onl/ mode frequencies are determined whereas for the measurement of permeability two or more resonant TM/sub onl/ mode frequencies are determined. The dielectric or magnetic properties are computed from the resonance frequencies, structure dimensions, and unloaded Q. Since the loss tangent is inversely proportional to the unloaded Q of the structure, the precision to which Q is measured determines the accuracy of the loss tangent.

2,648 citations

Book
01 Jan 1984
TL;DR: In this paper, the authors present a detailed description of the properties of solid state chemistry, including point groups, space groups, and crystal structure, as well as some factors which influence crystal structure.
Abstract: What is Solid State Chemistry? Preparative Methods. Characterization of Inorganic Solids: Application of Physical Techniques. Thermal Analysis. X-ray Diffraction. Point Groups, Space Groups and Crystal Structure. Descriptive Crystal Chemistry. Some Factors Which Influence Crystal Structure. Crystal Defects and Non-Stoichiometry. Solid Solutions. Interpretation of Phase Diagrams. Phase Transitions. Ionic Conductivity and Solid Electrolytes. Electronic Properties and Band Theory: Metals, Semiconductors, Inorganic Solids, Colour. Other Electrical Properties. Magnetic Properties. Optical Properties: Luminescence, Lasers. Glass. Cement and Concrete. Refractories. Organic Solid State Chemistry. Appendixes. Index.

2,106 citations

Journal ArticleDOI
TL;DR: In this article, a simple technique is described for ascertaining trial models for the structures of perovskites, which relies on an understanding of the fundamental components of the structure and rules are given for determining trial models rapidly.
Abstract: A simple technique is described for ascertaining trial models for the structures of perovskites. The method relies on an understanding of the fundamental components of the structure. Rules are given for determining trial models rapidly.

1,409 citations