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Ceramic BaZn1/3Ta2/3O3 for microwave applications

Ciceron A. Berbecaru 1Horia V. Alexandru 1Andrei Ioachim 2Mariana I. Toacsan Liviu Nedelcu 2Gabriel Banciu Rodica Ramer 2Ecaterina Andronescu 3Sorin Jinga 3Cornelia Jinga 3

1. University of Bucharest, Faculty of Physics, Bucharest-Magurele p.o.box mg-11, Bucharest 76900, Romania
2. National Institute of Materials Physics (NIMP), Atomistilor 105 bis, Bucharest 077125, Romania
3. University Politehnica of Bucharest, Polizu 1-7, Bucharest, Romania

Abstract

The BaZn1/3Ta2/3O3 is a member of the new perovskit oxide generation, widely used in high frequency domain. Their high permittivity 28-30, low losses and an excellent thermal stability on a large temperature scale, make them suitable for microwave applications. The ceramics are obtained by solid state reaction. Samples were sintered in air at 1550, 1600 and 1650 oC temperature range for 2 hours, followed by 10 h annealing at 1410 oC, to improve the material’s properties, [1, 2, 3]. Scanning Electron Microscopy, X-ray diffraction and Energy Dispersive X-ray analysis were performed to investigate the morphology and the structure of the ceramics. A secondary phase and the unit cell distortion were found from XRD data. The sintering temperature promotes a long-range order with a 2:1 ratio of Ta and Zn cations on the octahedral positions of the perovskite structure. A HIOKI 3522 LCR bridge was used to investigate the dielectric parameters of the BZT ceramics on 45 Hz ¸ 5 MHz frequency range, in conjunction with the Quatro Cryosystem on the temperature range -150 / +150 oC. A high stability of the permittivity was noticed. The dielectric properties measured in the microwave range were correlated with morphological and structural properties. The Hakki-Coleman method was employed to measure the dielectric constant of the samples. Typical values of 28 at 6 GHz were found and less than 6 ppm/deg positive temperature coefficient of the resonance frequency. To improve the microwave parameters of BZT (i.e. Q x f > 100,000 GHz), sintering temperatures greater than 1600 oC and annealing time higher than 10h were required.

References: [1] A. Ioachim et al, Thin Solid Films 516 (2008) 1558–1562. [2] F. Roulland et al, Materials Science and Engineering B104 (2003) 156–162. [3] A.Ioachim et al, J. Optoelectr. Adv. Mater. 9 (6) (2007) 1833-1838.

 

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Presentation: Poster at E-MRS Fall Meeting 2008, Symposium I, by Ciceron A. Berbecaru
See On-line Journal of E-MRS Fall Meeting 2008

Submitted: 2008-05-19 21:47
Revised:   2009-06-07 00:48