由於無線通訊的快速發展，因此如何去設計高品質、重量輕與低成本的元件，就成為重要課題。為了完成元件尺寸的縮小化與系統工作的高效率與穏定性，許多對介電共振器與微波元件基板的研究都聚焦在具有高品質因素，高介電常數與接近零的共振頻率溫度係數的介電材料上。 此外、降低介電材料的燒結溫度也是重要研究課題。就如之前所提的內容，本論文將以二個部份加以研究與探討：

1. 開發高介電常數、高品質因數與良好的頻率溫度穏定性的新微波陶瓷材料

[A] MgTiO3陶瓷系統的研究

(1) MgTiO3陶瓷系統運用在微波頻段是一個受歡迎的介電材料。當Mg:Ca比例為95:5，MgTiO3-CaTiO3陶瓷系統具有以下的介電特性：εr ~21，Q×f ~56,000 GHz （在7 GHz），以及τf ~ 0 ppm/℃
。它們已被發現可運用在諸如溫度補償型式的電容器，共振器與天線之方面。為了改善它的εr與Q×f值，利用Ca0.6La0.8/3TiO3 (εr ~109， Q×f ~ 17,600 GHz，τf ~ 213 ppm/℃) 取代CaTiO3將加以探討。
(2) 利用Zn部份取代MgTiO3陶瓷中的Mg，(Mg0.95Zn0.05)TiO3陶瓷仍然為鈦鐵礦結構且已被研究具有εr ~17.05， Q×f ~ 264,000 GHz與τf ~ - 40.31 ppm/℃之良好介電特性。為了形成溫度穏定的材料，將CaTiO3與(Mg0.95Zn0.05)TiO3混合。這兩相系統的微結構與微波介電特性將被探討。並以XRD來鑑定兩相系統。此外單相的(Mg0.95Zn0.05)TiO3陶瓷系統在本文中也會被探討。
(3) 非當量配製的Mg1+δTiO3+δ（-0.05≦δ≦0.05）陶瓷系統在本文中也將被探討。它們的介電特性與不同的δ值有關。當δ=0.02時，Mg1.02TiO3.02陶瓷系統在1400℃持溫4小時之下為單相的MgTiO3，且有良好的微波介電特性：εr ~18.28， Q×f ~ 357,600 GHz（在10 GHz），τf ~ -50 ppm/℃。本文也將提到介電特性與二次相MgTi2O5與Mg2TiO4的關係。

[B] Mg2TiO4陶瓷系統的探討

(1) Mg2TiO4陶瓷在微波頻段的應用上是另一個具有高品質因數，低價格的材料。它們具有立方結構且屬於空間群Fd-3m，並且擁有高介電常數（εr ~14），高品質因數（Q×f ~ 150,000 GHz），與負的τf值（τf ~ -50 ppm/oC）。當CaTiO3（τf ~ 800 ppm/℃）與Mg2TiO4混合，0.93Mg2TiO4-0.07CaTiO3被報導有良好的介電特性：εr ~15，Q×f ~ 35,000 GHz，τf ~ -2 ppm/oC。為了改善它們的介電特性，更好的組合(1-x)Mg2TiO4-xSrTiO3陶瓷系統將被探討。
(2) 本文也將對(Mg1-xZnx)2TiO4（0.01≦x≦0.09）陶瓷系統的配製與研究加以探討。當x=0.05時，(Mg0.95Zn0.05)2TiO4陶瓷在燒結溫度1330℃持溫4小時之下，有以下的介電特性：εr ~15.48，Q×f ~ 275,300 GHz，τf ~ -34 ppm/℃。為了形成溫度穏定的材料，SrTiO3、CaTiO3與(Ca0.8Sr0.2)TiO3將分別與(Mg0.95Zn0.05)2TiO4混合，這些兩相系統的微結構與微波介電特性將被探討。並利用XRD來鑑定兩相系統。

2. 微波平面濾波器的設計與製作

在本文中將提出尾端耦合微帶線慢波帶通濾波器，這些窄頻帶通濾波器使用了高介電基板去縮小尺寸。藉由尾端耦合結構可有效增加帶拒的寬度進而改善頻率的選擇性。在此使用了Al2O3（εr =9.7, tanδ=0.00036）與 0.85MgTiO3-0.15Ca0.6La0.8/3TiO3（εr = 25.45, tanδ= 0.00002）陶瓷基板，設計的中心頻率為1.8 GHz，文中也將提到濾波器的尺寸與頻率響應的實現。

Due to the development in wireless communication was rapidly, how to design the high quality, to make the demands of the light and low cost devices is very important. To achieve miniaturization of the dimensions of the devices and for the system work with high efficiency and stability, many researches have been focusing on developing dielectric materials with high quality factor (Q×f), high dielectric constant (εr) and near zero temperature coefficient of resonator frequency (τf) for the use of dielectric resonator and microwave device substrate. Moreover, reduce the sintering temperature of dielectric materials are also become mail studied. As mentioned above, the main investigation of this article is divided two parts to study and discuss.

1. Development novel microwave ceramic material which has high dielectric constant, high quality factor and microwave of high temperature stability:

[a] Study of MgTiO3 Ceramics

(1) Magnesium titanate (MgTiO3) ceramics is a popular dielectric material applied at microwave frequencies. With the Mg: Ca ratio of approximately 95:5, MgTiO3-CaTiO3 ceramics gives εr ~21, Q×f ~ 56,000 GHz (at 7 GHz), and τf~ 0 ppm/℃. It has found many applications in microwave systems such as in temperature-compensation-type capacitors, resonators and antennas. To improve the εr and Q×f values, replacing CaTiO3 by Ca0.6La0.8/3TiO3 (εr ~109, Q×f ~ 17,600 GHz, andτf ~ 213 ppm/℃) was investigated.
(2) With partial replacement of Mg by Zn in MgTiO3, the (Mg0.95Zn0.05)TiO3 ceramics also having an ilmenite-type structure was investigated to possess excellent dielectric properties withεr value ~ 17.05, a Q×f value ~ 264,000 GHz (at 7 GHz) , and τf~ -40.31 ppm/℃ To achieve a temperature-stable material, CaTiO3 was added to (Mg0.95Zn0.05)TiO3. The microstructures and the microwave dielectric properties of the two-phase system were investigated. Two-phase system was confirmed by the XRD patterns. Evaporation of Zn occurred at temperatures higher than 1300℃ and caused an increase in the dielectric loss of this system. In addition, single-phase (Mg0.95Zn0.05)TiO3 ceramics were also investigated in the topic.
(3) The non-Stoichiometry Mg1+δTiO3+δ (-0.05≦δ≦0.05) ceramic system were prepared and investigated in this topic. The dielectric properties were correlated with various δ values. At δ = 0.02, the excellent microwave dielectric properties of εr ~18.28, Q×f ~357,600 GHz (at 10 GHz), τf~ -50 ppm/℃ were obtained for Mg1.02TiO3.02 ceramics sintered at 1400℃ for 4 h with the single MgTiO3 phase. The correlation between the dielectric properties and the secondary phases MgTi2O5 and Mg2TiO4 is also proposed.

[b] Investigation of Mg2TiO4 Ceramics

(1) Magnesium orthotitanate (Mg2TiO4) ceramics are another high-Q low-cost material for microwave frequency applications. They have a cubic structure that belongs to the space group Fd-3m (227). They have a high dielectric constant (εr ~14), a high Q factor (Q×f value ~ 150,000 GHz), and a negativeτf value (-50 ppm/℃). When CaTiO3 (τf ~ 800 ppm/℃) was added to Mg2TiO4, 0.93Mg2TiO4-0.07CaTiO3 ceramic was reported to have excellent dielectric properties with an εr of ~15, a Q×f of ~ 35,000 GHz, and a τf of ~ -2 ppm/℃. In order to improve their dielectric properties, the better combination of (1-x)Mg2TiO4-xSrTiO3 ceramic system were investigated.
(2) In the topic, the dielectric resonators of (Mg1-xZnx)2TiO4 (0.01≦ x≦0.09) system were prepared and studied. At x = 0.05, a fine combination of microwave dielectric properties (εr ~15.48, Q×f ~ 275,300 GHz, τf ~ -34 ppm/℃) was obtained for (Mg0.95Zn0.05)2TiO4 specimen sintered at 1330oC for 4 h. To produce a temperature-stable material, SrTiO3, CaTiO3, and (Ca0.8Sr0.2)TiO3 were added to (Mg0.95Zn0.05)2TiO4, respectively. The microstructures and the microwave dielectric properties of these two-phase systems were investigated. Two-phase system was confirmed by the XRD patterns.

2. Design and fabrication of planar filters at the microwave frequency:

A band-pass filter of end-coupled microstrip slow-wave resonant is presented. In this article, using the high permittivity ceramic substrate to miniaturize the sizes of narrow-band band-pass filters is investigated. The selectivity and stop-band rejection of the designed filters can be improved significantly by utilizing an end-coupled structure. The responses of the fabricated filters using Al2O3 (εr=9.7, tanδ=0.000036) and 0.85MgTiO3-0.15Ca0.6La0.8/3TiO3 (εr=25.45, tanδ=0.00002) ceramic substrates are designed at a center frequency of 1.8 GHz. The compact size and performance of this class of filter are demonstrated in this topic.

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