Dielectric properties of BSTO/MgO ceramic composites

Author: Yang Chunxia   Zhou Hongqing   Liu Min   Wu Hongzhong  

Publisher: Springer Publishing Company

ISSN: 0957-4522

Source: Journal of Materials Science: Materials in Electronics, Vol.17, Iss.5, 2006-05, pp. : 347-352

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Abstract

Ba0.55Sr0.45TiO3/MgO ceramic composites with 50wt% MgO content were studied in terms of the phase distribution, microstructure and electric properties, prepared by traditional ceramic process-solid phase synthesis. The results show that a small amount of Mg2+ ions have entered BSTO lattices to substitute for Ti4+ and behave as electron acceptors, contributing to the decrease of the dielectric loss. Ba0.55 Sr0.45TiO3/MgO composites in the paraelectric state at room temperature still have a high tunability because of a field-induced hardening of the soft phonon and the presence of micro- or nano-polar phases in the paraelectric phase. For Ba0.55Sr0.45TiO3/MgO ceramic composites, the microwave loss at 2.5 GHz is 7.1 × 10−3 and the value of tunability is 13.8% with the external DC field 4 kV ⋅ mm−1. It can basically meet the requirements of phase shifters working at microwave frequencies. The phase shift of 122 was obtained at 9.2 GHz using the designed phase shifter with the bias voltage 2 kV ⋅ mm−1.

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