The aim of this work was to contribute to a better understanding of the characteristics and applications of (Ba,Sr)Sm2Ti4O12 microwave dielectric ceramics. The major contents are as follows. Firstly, to establish the correct reaction sequence of (Ba,Sr)Sm2Ti4O12, phases present in different calcining temperatures are identified by X-ray diffraction patterns. When different calcining temperatures are used, the source materials BaO (BaCO3), TiO2 and Sm2O3 are consumed at different calcining temperatures; the intermediate phases BaTiO3, BaTi4O9, and Sm2Ti2O7 reveals and consume at different calcining temperatures before the BaSm2Ti4O12 phase starts to reveal. However, the real solid reaction processes are usually more complex, and some intermediate reaction processes might happen.
Secondly, in the (Ba1-xSrx)Sm2Ti4O12 system, SrO can be used to substitute the BaO site and improve the microwave dielectric characteristics. In this study, we find that SrO content in the range of 2 ~ 6 mol% is the acceptable composition because of the higher Q*f values and acceptable and values. Thirdly, the CaO-BaO- Li2O-Sm2O3-TiO2(CBLST) ceramics system was studied. In general, a dielectric material with a high has a large . To adjust to close 0ppm/oC, two or more compounds having negative and positive values are employed to form a solid solution or mixed phases in order to obtain the desired dielectric properties. In this study, BaO was used to substitute the CaO site and improved the microwave dielectric characteristics.
Finally, the (Ba0.98Sr0.02)Sm2Ti4O12 system was adopted as a case of applications in dielectric resonator antenna. It possessed a low value of -5.96ppm/¢XC, a high value of 79, and a high Q*f value of 7920 GHz (at 3.311GHz). With the loading of a (Ba0.98Sr0.02)Sm2Ti4O12 dielectric resonator (DR), a circular polarization (CP) design of DR antenna through a cross slot of unequal slot lengths in the ground plane of a microstrip line is fabricated. From the results obtained, it is also found that the present proposed CP design has relatively relaxed manufacturing tolerances, as compared to the conventional CP designs that require slight geometrical modifications of the microstrip patch or DR elements. With the loading of a (Ba0.98Sr0.02)Sm2Ti4O12 superstrate layer and a 1W chip resistor, a compact rectangular microstrip antenna with enhanced gain and wider bandwidth can be implemented. The antenna size is reduced to be ~ 6.05% times of a conventional patch antenna, the proposed structure can have an operating bandwidth of more than six times that of a conventional patch antenna, with an almost equal antenna gain level.
| Identifer | oai:union.ndltd.org:NSYSU/oai:NSYSU:etd-0121102-105915 |
| Date | 21 January 2002 |
| Creators | Cheng, Ping-Shou |
| Contributors | Long Wu, Ying-Chung Chen, Chih-Yu Huang, Cheng-Fu Yang, Mao-Hsiung Chen, Mau-Phon Houng, Kuang-Chih Huang |
| Publisher | NSYSU |
| Source Sets | NSYSU Electronic Thesis and Dissertation Archive |
| Language | Cholon |
| Detected Language | English |
| Type | text |
| Format | application/pdf |
| Source | http://etd.lib.nsysu.edu.tw/ETD-db/ETD-search/view_etd?URN=etd-0121102-105915 |
| Rights | not_available, Copyright information available at source archive |
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