具高介電常數的鈦酸鋇/鎳複合材料之製程研究

Abstract

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。

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.