摻雜對鈦酸鋇陶瓷電容溫度穩定性之影響

Effects of dopants on the dielectric behaviors of barium titanate ceramics

林城興(Cheng-Hsing Lin)

指導教授 ： 王玉瑞 ； 王錫福

國立臺北科技大學/工程學院/材料科學與工程研究所/碩士(2007年)

摘要

隨著積層陶瓷電容(MLCCs)被應用至汽車電子元件之上，基於安全方面上的考量，材料必須符合EIA標準中的X8R特性(-55~150 oC，ΔC/C≦±15%)。目前鈦酸鋇主要的溫度穩定機制，是藉由雜質成份的添加，促使其顯微結構中化學組成不均勻，形成核殼結構(Grain core - Grain shell Structure)。所謂核殼結構中核心(core)部分為強電性正方相(Tetragonal)，而外殼(shell)部分則為順電性立方相(Cubic)；藉由改變微結構中核/殼間之比例，使居禮溫度(Tc)偏移並造成介電峰寬化，將介電溫度曲線平坦化，藉此讓材料達到X8R規格可應用的範圍。本研究藉由固態反應法製程，探討摻雜以及氧化物的添加對於鈦酸鋇陶瓷各項特性所造成的影響，並期待能夠合成符合X8R特性之鈦酸鋇陶瓷材料。
實驗結果顯示，隨著元素(La、Ho、Y)摻雜量的增加，會使材料之居禮溫度(Tc)產生偏移，並導致材料正方性(Tetragonality; c/a ratio)降低，鈦酸鋇也由正方相轉變為立方相，藉由改變鈦酸鋇結構中正方相與立方相之比例，調整材料之介電溫度特性，改善TCC變化率；另外，材料結構中之晶粒大小與密度也會隨元素(La、Ho、Y)摻雜量的增加而降低，燒結更加不易緻密化。

關鍵字

鈦酸鋇、摻雜 ； MLCCs ； 核殼結構 ； X8R ； TCC ； 居禮溫度(Tc)

並列摘要

In recent years, BaTiO3-based Multi-Layer Ceramic Capacitors (MLCCs) have been widely used in automotive applications. For safety reason, MLCCs need to satisfy X8R characteristic of the EIA standard (-55~150 oC，ΔC/C≦±15%). In present day, the mechanism of modifying the temperature dependency of dielectric properties is based on the chemical inhomogeneous structure so called “Grain core – Grain shell structure” caused by dopants. In this study, solid-state reaction method and doping different dopants (La2O3, Ho2O3, Y2O3) and additives were used to modify the dielectric properties of BaTiO3 ceramic and meet X8R characteristic. Experimental results show that the samples doped with different amount elements (La, Ho, Y) could shift the Curie temperature (Tc), modify the TCC behavior, decrease the grain size, density and tetragonality of ceramic,and cause the phase transition to cubic from tetragonal.

並列關鍵字

BaTiO3 ； Dopants ； MLCCs ； Core shell structure ； X8R ； TCC ； Curie temperature (Tc)

參考文獻

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