具高介電常數的鈦酸鋇/鎳複合材料之製程研究

Percolative BaTiO3/Ni Composites with Improved Dielectric Constant

陳旭昇(Shiu-Sheng Chen)

指導教授 ： 段維新

國立臺灣大學/工學院/材料科學與工程學研究所/碩士(2008年)

https://doi.org/10.6342/NTU.2008.00946

摘要

摘要

陶瓷-金屬複合材料的性質在接近Percolation Threshold時會有重大的轉變，例如:介電常數急遽增加、電阻值突然下降等等。本研究製備了兩個試樣系統，BaTiO3/Ni(NO3)2系統及BaTiO3/Ni系統。在氮氣氣氛中燒結後，兩個系統皆可得到BaTiO3/Ni複合材料。探討金屬Ni的添加對BaTiO3的介電性質及顯微結構的影響。
實驗結果顯示，純BaTiO3試樣在1300℃燒結後，其微結構僅有小晶粒；當燒結溫度大於1330℃時，會因共晶液相的幫助而發生異常晶粒成長。電性量測的結果顯示，在1300℃時有最高的相對介電常數( )，BaTiO3試樣經過氮氣氣氛燒結後仍處於絕緣狀態(1012 )。
關於BaTiO3-Ni複合材料，XRD結果顯示BaTiO3與Ni不會發生化學反應；相對密度在燒結溫度為1370℃時為最佳；EPMA結果顯示，在氮氣氣氛燒結後，所有Ni顆粒的表面因氧化而覆蓋一層NiO層。關於BaTiO3/Ni(NO3)2系統，在燒結溫度為1330℃時，試樣的相對介電常數在接近Percolation Threshold (34.3 vol%Ni)時展現極高的值( )；BaTiO3/Ni系統則是發生在燒結溫度為1370℃且Ni含量為36vol%時，試樣的相對介電常數約為170000。磁性量測結果顯示，試樣的磁化強度隨著Ni含量的增加而增加，在Ni添加量為36vol%時的飽和磁化強度約為25emu/g。

關鍵字

鈦酸鋇 ； 鎳 ； Percolation ； 介電常數 ； 介電損失 ； 異常晶粒成長 ； 電阻率 ； 多層陶瓷電容器

並列摘要

Abstract

The properties of ceramic-metal composites exhibit significant change in the neighborhood of percolation threshold, for examples: the dielectric constant increases rapidly and the resistance decreases abruptly. In the present study, two specimen series, BaTiO3/Ni(NO3)2 and BaTiO3/Ni systems are prepared by sintering in N2. The BaTiO3/Ni composites are obtained. The effect of Ni content on the microstructure and the dielectric properties of Ni-doped BaTiO3 are investigated.
The experimental results show that the microstructure of BaTiO3 specimen sintered at 1300℃ is composing of only fine grains. When the sintering temperature is above 1330℃, the abnormal grain growth can take place due to the presence of an eutectic liquid. The dielectric constant of BaTiO3 specimen is the highest after sintering at 1300℃( ). The BaTiO3 specimen is insulating after sintering in N2 (1012 ).
For the BaTiO3-Ni composites, the XRD patterns show there is no chemical reaction between BaTiO3 and Ni. The relative density is the highest after sintering at 1370℃. The EPMA analysis shows that Ni particles are surrounded by a layer of NiO because of the oxidation. For the BaTiO3/Ni(NO3)2 system, the dielectric constant of the specimens in the neighborhood of the percolation threshold (34.3vol%Ni) exhibits extraordinarily high value when the sintering temperature is 1330℃( ). The dielectric constant of BaTiO3-36vol%Ni specimens after sintering at 1370℃ is about 170000. The magnetic results show that the magnetization increased with increasing Ni content. The specific saturation magnetization of BaTiO3-36vol%Ni composites is about 25 emu/g.

並列關鍵字

BaTiO3 ； Ni ； percolation ； dielectric constant ； dielectric loss ； abnormal grain growth ； resistivity ； MLCCs

參考文獻

2. H. Kishi, Y. Mizuno and H. Chazono, “Base Metal Electrode Multilayer Ceramic Capacitors Past Present and Future Perspectives”, Jpn. J. Appl. Phys., 42, 2003, 1-15.

3. H. Emoto and J. Hojo, “Sintering and Dielectric Properties of BaTiO3-Ni Composite Ceramics”, J. Ceram. Soc. Jpn., 100, 1992, 553-557.

4. C. Pecharromán, E. B. Fátima, J. F. Bartolomé, L. E. Sonia and J. S. Moya, New Percolative BaTiO3-Ni Composites with a High and Frequency-Independent Dielectric Constant, Adv. Mater., 13, [20], 2001, 1541-1544.

5. R. Chen, X. Wang, H. Wen, L. Li and Z. Gui, “Enhancement of Dielectric Properties by Additions of Ni Nano-Particles to a X7R-Type Barium Titanate Ceramic Matrix”, Ceram. Int., 30, 2004, 1271-1274.

6. Z. Chen, J. Huang, Q. Chen, C. Song, G. Han, W. Weng and P. Du, “A Percolative Ferroelectric–Metal Composite with Hybrid Dielectric Dependence”, Scripta Mater., 57, 2007, 921-924.