Bismuth titanium indium antimony oxide: A low-temperature-coefficient, high-K dielectric material
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Y.L. Qin and H.W. Zandbergen National Institute for HREM, Laboratory for Materials Science, Delft University of Technology, 2628 AL Delft, The Netherlands (Received 8 March 2000; accepted 28 August 2000)
The 1 MHz dielectric properties for mixed-phase polycrystalline ceramics in the system Bi4Ti3O12–Bi(InxSb1−x)O3 were reported. In the vicinity of ambient temperature, the dielectric constants for the Sb and In end-members were approximately 430 and 160, respectively, and the temperature coefficients of dielectric constant (TCKs) were approximately −7600 and +430 ppm/deg. At an overall composition of Bi4Ti3O12:Bi(In0.37Sb0.63)O3 a dielectric constant of 144 and a low TCK were found. Powder x-ray diffraction and electron microscopy analyses indicated that the optimal composition contained three major phases. Deviation of any of the elements from the above ratio leads to degradation of the properties.
I. INTRODUCTION
The demands for miniaturization of microwave communications technologies require continuing discovery and development of new materials. To meet the requirements for use in microwave resonators and filters, dielectric materials must satisfy stringent physical property requirements, greatly restricting the number of materials which can be considered for use. These requirements are, in the vicinity of ambient temperature, the largest possible dielectric constant (K), the lowest possible dielectric loss (high Q), and the lowest possible temperature coefficient of dielectric constant (TCK), properties which are generally mutually exclusive. Several materials are currently under active development for such use, based on barium titanates or tantalates and zirconium tin titanate, with dielectric constants in the range 20–90, Q values in the range of 20,000–2,000 (lower for the materials with higher dielectric constants), and TCKs of less than 10 ppm/deg.1,2 Here we report the initial characterization of a new type of dielectric material which may be a possibility for such applications: a multiple-phase Tibased ceramic of composition Bi4Ti3O12:Bi(InxSb1−x)O3, with x ⳱ 0.37. The material has a dielectric constant of approximately 140 and a low TCK, due to the balancing of positive and negative temperature coefficients in different constituent phases right at ambient temperature. Qs in the range 100–500 are found. Thus, the relatively a)
Also at the Department of Chemistry and Materials Institute, Princeton University, Princeton, NJ 08544.
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http://journals.cambridge.org
J. Mater. Res., Vol. 15, No. 12, Dec 2000 Downloaded: 27 Mar 2015
high dielectric constant appears to trade off against a decreased Q. The optimal material properties are particularly sensitive to the Sb:In ratio.
II. SYNTHESIS AND CHARACTERIZATION
The Aurivelius family of layered structure oxides3 are well known for their ferroelectric properties. In particular the compound SrBi2Ta2O9 has been of significant recent interest. 4 The related compounds Bi 4 Ti 3 O 12 and BaBi4Ti4O15 served as the starting point for this investigation. Chem
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