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  • 學位論文

利用全頻譜與掃描微探顯微術研究微波材料的介電機制

Study on Dielectric Mechanisms of Microwave Materials by Using Full-Band Spectroscopy and Scanning Probe Microscopy

指導教授 : 鄭秀鳳 林諭男
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摘要


本研究報告主要是利用全頻段介電譜及微波近場顯微鏡來研究微波介電材料之本質(intrinsic)及非本質(extrinsic)的介電機制。主要研究的材料是高介電常數的Bi1.5Zn1.0Nb1.5O7及高品質因子的Ba(Mg1/3Ta2/3)O3介電陶瓷,研究的目的是探討造成微波介電材料高介電常數或高品質因子的本質機制。 全頻譜介電特性量測中,所包含的頻段有: 低頻(1 kHz-3 MHz),微波頻段(~GHz),次毫米波段(THz),紅外光頻段,以及可見光頻段。將詳細探討各頻段中主要的極化機制,以及不同頻段極化機制的關聯性。 在Bi1.5Zn1.0Nb1.5O7 陶瓷的立方黃綠石(cubic pyrochlore)結構A2B2O6O’1中, A及 O’ 原子平衡位置無序的分佈(displasive disorder)對微波頻段及低頻段的介電特性有很大的影響。A位置大部分被極化率高的鉍離子(Bi3+)所佔, 而無序的A, O’分佈也加強離子極化的強度,因此A-O 及 A-O’ 相關的晶體振盪模式對離子極化有很強的介電貢獻,但又由於無序的結構造成A-O 及 A-O’ 相關的晶體振盪模式具有極大的振盪阻尼,也因此造成Bi1.5Zn1.0Nb1.5O7 材料在微波頻段有相較於其他微波材料高的介電常數及介電損失。相較於高介電常數的Bi1.5Zn1.0Nb1.5O7陶瓷, 高品質因子的 Ba(Mg1/3Ta2/3)O3介電陶瓷本質機制則稍有不同,其主要的介電貢獻則是來自鈣鈦礦結構 (perovskite)中鍵結較為緊密的B”O6 氧化物的八面體。結果顯示微波介電常數與氧化物八面體緊密程度有關,而微波頻段的品質因子則與氧化物八面體的扭曲變形程度有關。 在非本質機制的研究上,微波近場顯微探針掃描所得的影像清楚顯示在微波介電特性較差的陶瓷通常含有低介電常數及低品質因子的二次相。此外, 結合掃描式顯微拉曼(Micro Raman)光譜,可觀察到八面體扭曲的晶粒存在,此種八面體扭曲的晶粒及二次相可視為陶瓷中主要的非本質損失來源。

並列摘要


In this study, full-band dielectric spectroscopy and microwave evanescent microscopy were used to study the intrinsic and extrinsic dielectric mechanism of microwave dielectric materials. Bi1.5Zn1.0Nb1.5O7 and Ba(Mg1/3Ta2/3)O3 ceramics are investigated to reveal the mechanisms for high dielectric constant and high quality factor, respectively. The studied spectrum regimes include: low-frequency band (1 kHz-3 MHz), microwave frequencies (~GHz), submillimeter wave (THz) band, infrared frequency band, and optical (visible light) band. The dominant polarization mechanisms in each band are studied, and the correlation between these mechanisms is discussed. Displasive disorders are found in both the A and O’-sites of Bi1.5Zn1.0Nb1.5O7 pyrochlore structure, A2B2O6O’1, which have significant influences on the dielectric properties of the materials at microwave (~GHz) and lower frequency (1 kHz-3 MHz) bands. The highly polarizable A-site ions, Bi3+, and the asymmetries at A- and O’-sites cause prominant dielectric contributions from A-O and A-O’ related modes, resulting in high dielectric constants at microwave frequencies. Large damping coefficients of these modes also lead to high dielectric losses. In contrast, the displacement disorders mechanism is not operating for high-Q Ba(Mg1/3Ta2/3)O3 ceramics and the dominant dielectric mechanism for theses materials is the polarization of rigid B”O6 octahedra in the complex perovskite structure A(B’1/3B”2/3)O3. Microwave dielectric constants are influenced by the rigidity of the three-dimensional oxygen-octahedron network, while the microwave quality factors, Q×f values, are related to the distortion of B”O6 oxygen octahedron. In the study of extrinsic mechanism, EMP images reveal that samples with inferior dielectric properties usually contain large proportion of low-K and low-Q secondary phase. Moreover, scanning Raman spectroscopy reveals the presence of grains with distorted crystal structure. These defects degrade the macroscopic dielectric properties, and are the main extrinsic mechanisms modifying ceramic properties.

被引用紀錄


黃裕清(2005)。奈米級鑭鍶錳氧化物與微波介電陶瓷製程之研究〔碩士論文,國立臺灣大學〕。華藝線上圖書館。https://doi.org/10.6342/NTU.2005.01061
吳明忠(2004)。鋅鈮系無線通訊用低溫燒結微波介電材料之研究〔碩士論文,國立臺灣大學〕。華藝線上圖書館。https://doi.org/10.6342/NTU.2004.01796
陳昱文(2006)。臨場監控雷射鍍膜法合成高介電常數薄膜電性、光性、微波特性研究〔碩士論文,國立臺灣師範大學〕。華藝線上圖書館。https://www.airitilibrary.com/Article/Detail?DocID=U0021-0712200716124365

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