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Electric State and Chemical Bonding of (Mg4−xMnx)Nb2O9 Microwave Dielectric Ceramics

Published online by Cambridge University Press:  03 March 2011

Akinori Kan ,
Hirotaka Ogawa  and
Atsushi Yokoi
Akinori Kan*
Affiliation:
Faculty of Science and Technology, Meijo University, Tempaku-ku, Nagoya 468-8502, Japan
Hirotaka Ogawa
Affiliation:
Faculty of Science and Technology, Meijo University, Tempaku-ku, Nagoya 468-8502, Japan
Atsushi Yokoi
Affiliation:
Faculty of Science and Technology, Meijo University, Tempaku-ku, Nagoya 468-8502, Japan
*
a) Address all correspondence to this author. e-mail: [email protected]
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Abstract

Solid solutions of (Mg4−xMnx)Nb2O9 (MMN), which have a corundum-type structure, showed a single phase over the entire composition range, and lattice parameters of MMN linearly increased with increased composition x. From the calculation of cation–oxygen bonds in NbO6 and MO6 (M = Mg and Mn) octahedra, it was found that the covalency of the Nb–O bond was decreased by the Mn substitution for Mg; the molecular orbital calculation in (NbM12O45)−61 cluster models also revealed that the covalency of the Nb–O bond in the (NbMn12O45)−61 cluster model is smaller than that of the Nb–O bond in the (NbMg12O45)−61 cluster model. This result is attributed to the differences in the density of state, which arise from the overlap population of Mg-3d, Mn-3d, Nb-5s, and O-2p orbitals. The dielectric constant and Q⋅f values varied from 11 to 16 and from 210,000 to 50,000 GHz, respectively. Thus, it is considered that these variations in the microwave dielectric properties may be related to the covalency of the cation–oxygen bonds.

Keywords

CeramicDielectricX-ray diffraction (XRD)
Type
Articles
Information
Journal of Materials Research , Volume 20 , Issue 9 , September 2005 , pp. 2456 - 2461
Copyright
Copyright © Materials Research Society 2005

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References

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