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Conference: Bucharest University Faculty of Physics 2006 Meeting

Section: Solid State Physics and Materials Science

Title:

BST Solid Solutions Ceramics for Microwave Applications.

Authors:

C. Berbecaru, L. Nedelcu*, A. Dutu*, A. Ioachim* Luciana Georgescu, H.V.Alexandru

Affiliation:

Faculty of Physics, Bucharest University,

*National Institute of Materials Physics, Bucharest-Magurele

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Keywords:

Abstract:

Solid solutions of full solubility, BaTiO3 and SrTiO3, called BST for short, are promising materials to be used in usual electronic and microwave devices. Undoped and doped samples (1% Mn and 1% Mg) were prepared by standard solid state reaction. Special emphasis was put on compositions x = 0.35 and 0.60 in the formula Ba1-xSrxTiO3, which are very attractive for microwave components [1,2]. Samples were sintered at temperatures 1200, 1220, 1230 and 1260 oC, for 2 hours. The dielectric permittivity and losses were measured walking up and down the temperature in the range -150 and 150 oC, at a rate less than 2 oC/min. Permittivity and losses were measured at the frequency of 1 kHz, with a Hioky RLC bridge and authomatically recorded every 10 seconds on the computer. Permittivity peak values increases from 2000 to 4000 with the sintering temperature increase. The Curie temperature of BST samples with x=0.35 and x=0.6 is in agreement with the Curie point dependence on Sr content, previously reported [3]. Furthermore an unusual cubic-rhomboedric transition for x=0.6 was noticed. At room temperature both parameters were measured also measured in microwaves range (1-1.7 GHz). References: [1] H.V.Alexandru, C.Berbecaru, A.Ioachim et al, MATER. SCI. ENG. B, 118 (2005) 92-96. [2] A.Ioachim, H.V.Alexandru, C.Berbecaru et al, MATER. SCI. ENG. C, (in press). [3] H.V.Alexandru, C.Berbecaru, A.Ioachim, APPLIED SURFACE SCIENCE, (in press).