Chemical bonding characteristics and dielectric properties of Nd2(Ba1−xSrx)ZnO5 solid solutions

2003 ◽  
Vol 18 (10) ◽  
pp. 2427-2434 ◽  
Author(s):  
Akinori Kan ◽  
Hirotaka Ogawa ◽  
Kenkichi Mori ◽  
Hitoshi Ohsato ◽  
Yoshinori Andou
Keyword(s):  
Crystal Structure ◽  
Dielectric Properties ◽  
Dielectric Property ◽  
Solid Solutions ◽  
Dielectric Constants ◽  
First Principle ◽  
Quality Factors ◽  
Microwave Dielectric ◽  
The Relationship ◽  
Bonding Characteristics

The relationship between the microwave dielectric property and crystal structure of Nd2(Ba1−xSrx)ZnO5 solid solutions was investigated using bond valence theorem and first principle method (DV-Xα method). The evaluation of the covalence characteristics of cation–oxygen bonds revealed that as the x value increased, the covalence characteristics of the M–O (M = Ba and Sr) bonds in the MO10 polyhedron decreased while those of the Zn–O(2) bonds in the ZnO4 tetrahedron increased. From the DV-Xα method, it was found that the 3d electrons of the Zn2+ ion are closely related to the strong covalence characteristics of the Zn–O(2) bonds. The dielectric constants were approximately constant over the whole composition; this result is considered to relate to the decrease in the covalence characteristic of the M–O bonds. The quality factors increased from 4915 to 25,836 GHz, and the grain growth of the solid solutions are considered to improve the Q × f values.

Influence of (Al1/3W2/3)5+ co-substitution for Nb5+ in NdNbO4 and the impact on the crystal structure and microwave dielectric properties

2018 ◽  
Vol 47 (44) ◽  
pp. 15808-15815 ◽  
Author(s):  
Hongcheng Yang ◽  
Shuren Zhang ◽  
Hongyu Yang ◽  
Ying Yuan ◽  
Enzhu Li
Keyword(s):  
Crystal Structure ◽  
Dielectric Properties ◽  
Ir Spectrum ◽  
Microwave Dielectric Properties ◽  
Complex Chemical ◽  
Microwave Dielectric ◽  
Bond Theory ◽  
Chemical Bond Theory ◽  
The Impact ◽  
The Relationship

The relationship between structure, bond characterizations and microwave dielectric properties of NdNb1−x(Al1/3W2/3)xO4 (0.03 ≤ x ≤ 0.07) ceramics was characterized by complex chemical bond theory and IR spectrum.

B-O Bond Character and Microwave Dielectric Properties of (1-x)CaTiO3-xCa(Zn1/3Nb2/3)O3 Perovskite Ceramics

2009 ◽  
Vol 421-422 ◽  
pp. 69-72
Author(s):  
Jie Shen ◽  
Wen Chen ◽  
Jing Zhou ◽  
Jie Zhu ◽  
Qiong Lei
Keyword(s):  
Dielectric Constant ◽  
Dielectric Properties ◽  
Microwave Dielectric Properties ◽  
Dielectric Materials ◽  
Solid State Reaction Method ◽  
Dielectric Constants ◽  
Identical Result ◽  
Microwave Dielectric ◽  
Calculation Results ◽  
The Relationship

The relationship between the character of the B-site cation–oxygen bond and the microwave dielectric properties in perovskites dielectric materials was studied in this paper. The atomic net charge of CaTiO3 (CT) and Ca(Zn1/3Nb2/3)O3 (CZN) was calculated respectively. The calculating result implies that the covalency of B-O bonds in CZN is stronger than that in CT. This predicted that the dielectric constant and loss of the ceramics will decrease after CZN incorporated in CT. To confirme the prediction, (1-x)CT-xCZN microwave dielectric ceramics were prepared by solid state reaction method with ZnNb2O6 as precursor. The structure analysis in terms of tolerance factor gives an identical result as calculation. The microwave dielectric properties, such as dielectric constants, Q×f values and τf were studied as a function of composition. With x increasing from 0.2 to 0.8, the dielectric constant linearly decreases from 109 to 49.37, the Q×f value increases from 8,340 to 13,200 GHz, and τf decreases from 321 to -18 ppm/°C. The properties trends are consistent with the previous calculation results, and confirm the relationship between the character of B-O bond and dielectric properties.

Crystal Structure–microwave Dielectric Property Relations in R2BaZnO5 (R= Sm, Eu, Gd, Dy, Ho, Er, and Tm) Ceramics

2002 ◽  
Vol 17 (7) ◽  
pp. 1803-1807 ◽  
Author(s):  
Akinori Kan ◽  
Hirotaka Ogawa
Keyword(s):  
Crystal Structure ◽  
Dielectric Properties ◽  
Microwave Dielectric Properties ◽  
Dielectric Constants ◽  
Orthorhombic Crystal ◽  
Ionic Radii ◽  
Orthorhombic Crystal Structure ◽  
Property Relations ◽  
Microwave Dielectric ◽  
Bond Valence Sum

R2BaZnO5 (R = Sm, Eu, Gd, Dy, Ho, Er, and Tm) were synthesized, and the effects of the differences in ionic radii of R ions on the microwave dielectric properties and crystal structure have been investigated by using x-ray powder diffraction. It was shown that the R2BaZnO5compounds have an orthorhombic crystal structure with Pnma (No. 62) and the lattice parameters of the samples increase linearly with the increase in the ionic radii of the R ions. The dielectric constants (εr) of R2BaZnO5sintered at the optimum temperatures vary linearly from 16.1 to 19.3, suggesting that these variations in εr are the result of the differences in the ionic polarizabilities of R ions. Moreover, it is suggested that the variations in the valences of R ions determined by using bond valence sum may exert an influence on quality factor (Qf ), because the values of valences of R ions in R(1)O7 polyhedra and Qf exhibit similar tendencies with changes in the ionic radii of R ions. In the R2O3–BaO–ZnO system, Dy2BaZnO5showed the appropriate microwave dielectric properties: εr = 17.1, Qf = 29669 GHz, and τf = −1.5 ppm/°C.

Effects of Ta5+ Substitution on Structure Transition and Microwave Dielectric Properties of Zn(Nb1-xTax)2O6 Ceramics

2007 ◽  
Vol 336-338 ◽  
pp. 265-268 ◽  
Author(s):  
Ying Chun Zhang ◽  
Xiu Hong Yang ◽  
Zhen Xing Yue ◽  
Fei Zhao ◽  
Long Tu Li
Keyword(s):  
Crystal Structure ◽  
Dielectric Properties ◽  
Microwave Dielectric Properties ◽  
Network Analyzer ◽  
Microwave Dielectric Ceramics ◽  
Zero Temperature ◽  
Quality Factors ◽  
Structure Transition ◽  
Microwave Dielectric ◽  
Dielectric Ceramics

The crystal structure, phase relation, microstructure and dielectric properties of microwave dielectric ceramics comprised of Zn(Nb1-xTax)2O6 were investigated systematically using XRD, SEM and a network analyzer in this study. XRD results show that the Zn(Nb1-xTax)2O6 ceramics have the orthorhombic for all x values. However, two kinds of solid solutions phase regions based on columbite structure and ZnTa2O6 structure were observed. SEM results show that the growth of grains is restrained with increase of Ta content in Zn(Nb1-xTax)2O6 ceramics. The dielectric properties exhibited a significant dependence on the crystal structure and compositions of the ceramics. The dielectric constant (εr) of Zn(Nb1-xTax)2O6 ceramics increased with increasing Ta content. However, the quality factors (Q×f) of this system show a different trend, and decrease with increasing Ta content. At x=0.65, a zero temperature coefficient of resonant frequency ( τ f) can be realized in Zn(Nb1-xTax)2O6 ceramics system.

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