| 摘要: | 為了降低燒結AlN陶瓷的成本，有必要研究出低溫燒結AlN陶瓷的製程。本研究以此為動機，選用La2O3、Y2O3兩種液相燒結助劑，放入高溫爐進行低溫燒結。探討在1300℃、1400℃、1500℃利用液相燒結的方式，燒結緻密化後的三種AlN陶瓷做相對密度與收縮率比較，並且將二次相的組成以及微結構做分析與介電特性的量測。
實驗發現燒結溫度越高、持溫時間越長，有添加燒結助劑，對於AlN陶瓷緻密度提升越好。但因添加燒結助劑，液相燒結的機制和持溫時間過長也使氧含量和介電損失ε”提高。利用4294A阻抗分析儀來量測AlN陶瓷，我們由Nyquist圖可以得知AlN陶瓷導電方式是電子通過晶界導電，而不是用晶粒導電。經由Colt-Colt plot圖的分析，得知隨著頻率的增加，介電常數ε’會下降。由介電常數ε’與頻率探討AlN陶瓷的極化機制，得知AlN陶瓷的極化機制為空間電荷極化，極化頻率範圍是1-104Hz。比較添加La2O3、Y2O3當燒結助劑的AlN陶瓷與純AlN陶瓷的介電性質，對三種AlN陶瓷做介電常數ε’、介電損失ε”比較，在頻率1MHz求得AlN介電常數ε’介於6~7之間，以及晶粒粒徑變大導致介電常數與介電損失也隨之增大。
In order to reduce the cost of sintered AlN ceramics, the need to develop low-temperature sintering of AlN ceramics process has caught our attention, as a motivation for this study. Two kinds of liquid-phase sintering additives, La2O3 and Y2O3, were chosen to achieve the low-temperature sintering process. The relative sintered density and shrinkage of AlN ceramics at sintering temperatures of 1300 ℃, 1400 ℃, and 1500 ℃ respectively were carefully estimated. The composition and microstructure of the second phase produced during sintering process were investigated, as well as the effect of second phases on the dielectric properties of AlN ceramics were intensively analyzed.It was found in this study that the higher sintering temperature, the longer sinterng time, and sintering additives contributed to enhance the density of AlN ceramics. However, the oxide sintering additives, which induced liquid-phase sintering and produced the second phase in consequence, and the growth of grain size caused the increase of oxygen impurity and dielectric loss ε”. We have learned from the Nyquist plots by using 4294A impedance analyzer to measure the AlN ceramics, the electronic conductivity of AlN ceramics is by the path of grain boundaries, rather than the grain. From Colt-Colt plot analysis, it was observed that the dielectric constant ε’ decreases as the frequency increases. The polarization mechanism of AlN ceramics was found to be space charge polarization in the range 1-104Hz. When compare the dielectric properties of add La2O3, or Y2O3 as sintering additives to pure AlN ceramic, the dielectric constant obtained in the frequency of 1MHz ε' were between 6 and 7 for same sintering process. However the larger grain size leads to the increase of loss tangent (tanδ), dielectric loss ε”, and dielectric constant ε’. |
