The objective of this study is to determine the effect of milling on the X-Band microwave properties of Ba,, ,TiO, / MgO {wt% MgO= 0 to 60 wt%} composites. At low frequency, the effect of the reduction of the overall particle size of the materials from attritor milling is dependent on the additive oxide content; for samples with oxide content > 5.0 wt%, the dielectric constant, and tunability (%) are decreased. Whereas, milled Ba,,Sr,,TiO, / MgO"' (wt% MgO= 0 to 1 wt%} composites exhibit low loss tangents, higher tunabilities, and higher dielectric constants than unmilled samples. The present study is focused on the effect of milling on the diekectric properties of Ba, ,Sr,,TiO, / MgO composites at microwave frequency. The samples were evaluated in a 10 GHz resonator cavity. Additionally, the effect of barium content and MgO content on the 10 GHz dielectric properties of Ba$r,.,TiO, (x = 0.45, 0.50, 0.55, 0.60) / MgO (MgO = 1 -60 Wt%) are investigated. These results are correlated with relevant material characterization techniques including FT-Raman studies. 342/[862]J. SYNOWCZYNSKI r t ul.
Ceramic compositions of barium strontium titanium oxide (BSTO) have been formulated for applications as pyroelectric sensor materials. The material has been fabricated in tape-cast and thin film forms. In general, the materials demonstrated high pyroelectric coefficients (p) accompanied with low dielectric constant and low dissipation factor. The compositions of the tape-cast and thin film specimens examined in this paper include a well-known commercially adopted Ba0.64Sr0.36TiO3 as well as a composition suggested in the literature, and a patented composition with the addition of MgO to BSTO is investigated. Doping BSTO with MgO has been shown to reduce the dielectric constant and loss tangent (over a very wide frequency range from 100 Hz-10 GHz) of the material and thereby increase the pyroelectric figure of merit. This article will discuss the processing, material characterization, pyroelectric coefficient, and pyroelectric figure-of-merit of the above mentioned BSTO compositions.
As the search continues for low-cost and highperformance components for the front-end devices for wireless communications systems, focus has been on the use of MEMS technology; but some attention has recently been given to exploring new and innovative designs based on the Ferroelectric and the Continuous Transverse Stubs (CTS) technologies. In this paper we present new phase shifter designs and an integrated phased array antenna system based on the use of multilayer Ferroelectric materials. Simulation results show that with the appropriate selection of the materials properties and the dimensions of the multilayer dielectric system, insertion losses may be reduced by as much as a factor of 100. These results also show that while only a slight reduction (15%) in the maximum achievable tunability was observed, it was possible to achieve significant improvement in the impedance matching characteristics. A procedure to enhance the radiation efficiency from an integrated Ferroelectric/CTS phased antenna array design will be described and specific array designs will be discussed.
Ceramic composites of barium strontium titanate and other non-ferroelectric oxides have been fabricated for use in phased array antennas. These composites have shown superior electronic properties at low and microwave frequencies in that they have reduced dielectric constants, low loss tangents and high tunabilities. However, minimal work (other than x-ray powder diffraction) has been reported on the correlation of these electronic properties to the site substitutions and the sample topography. Raman and FTIR spectroscopy has been used to study the structural properties related to the additions of both strontium to the barium titanate crystal structure as well as the effect of the additions of oxide 111 on Bal.xSrxTi03 (1-x = 0.00, 0.15, 0.30, 0.40, 0.45, 0.50, 0.55, 0.6,0.7,0.80, and 1.0). The optical properties of the ceramic composites have been correlated to the electrical properties of the materials such as the Curie temperatures and these results will be discussed in detail. I. IhTRODUCTlONPhased array antennas can steer transmitted or received signals either linearly or in two lmensions without mechanically oscillating the antenna. In order to make these devices available for many other commercial and militaTy uses, the basic concept of the antem must be improved. If ferroelectric materials could be used for the phase shifting element instead of ferrites, phased array antennas would be totally revolutionized.A ceramic Barium Strontium Titanate, Bal,SrxTi03, (BSTO), phase shifter using a planar microstrip construction has been demonstrated at 5-10 GHz. [1,2] BSTO/Oxide E l (designated as oxide III as the materials are undergoing the patent filing process) composites have shown greatly improved electronic properties at both low (KKz-MHz) to microwave frequency regions (10 GHz).[3] Most notably the loss tangents have been reduced to less than 0.002. [4] However, in order to improve the already adequate performance of the antennas, we have investigated composites with even lower loss tangents. We have therefore fabricated Bal-,SrxTi03 (BSTO) ceramics with a various molar ratios 0.55, 0.60, 0.70, and 1.00. The electronic properties of all of the above named compositions were then examined Additionally, Fourier transfm Raman and irhared spectroscopy was utilized to characterize . the BSTO composite as a function of the Ba / ratio and the site substitution of oxide JJI. Subsequently it was found that the materials containing barium content, 0.45, 0.50, 0.55 and U.S. Government work n o t p r o t e c t e d by U.S. copyright. O f barium, including, 1-x = 0.00, 0.30, 0.40 ,0.45, 0.50, 0.60 were the most promising in terms of the electronic properties appropriate for use in phased array antennas. Therefore, composites of B%.45Sr0.55Ti03, BW.50Sr0.50Ti03, B%.55Sr0.45Ti03, and B%.60Sr0.40Ti03/ Oxide III were fabricated and the electrical properties and optical properties were obtained. II. EXPERIMENTAL A. Ceramic Processing Powder forms of Barium Titanate and StrontiumTitanate were obtained fiom Ferro Corporation, Tran...
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