摘要
在-160℃—200℃温度范围内、0.1 Hz—0.1 MHz频率范围内测量了ZnO压敏陶瓷的介电频谱,发现可以采用电导率谱低频端的类直流特性来表征晶界Schottky势垒的电子输运过程,获得的Schottky势垒高度为0.77 eV.基于背靠背双Schottky势垒模型,提出当存在直流偏压时,势垒高度将随直流偏压线性增大.基于此势垒模型计算了ZnO压敏陶瓷单晶界的直流偏压大小,进而计算出晶粒平均尺寸为6.8μm,该理论值与通过扫描电子显微镜断面照片获得的测量值的偏差在5%以内.可见采用介电谱不但可以获得势垒高度实现电气性能的表征,还能获得晶粒尺寸实现显微结构的表征.
In this paper, the dielectric spectra of ZnO varistor ceramics are measured by Novocontrol wide band die}eetric spectrometer in a temperature range of -160 ~C-200 ~C and frequency range of 0.1 Hz-0.1 MHz. It is found that electron transportation can be characterized by the flat region on a low frequency side of ~r＇-f curve. The Schottky barrier height is 0.77 eV obtained from crl-f curve, which is consistent very well with the data from 1-V curves given in other literature. On the basis of back-to-back double Schottky barrier model, Schottky barrier height corresponding to electron transportation across grainboundary is explained to be the energy difference between interface state and barrier top. According to this explanation, Schottky barrier height will increase linearly with the increase of DC voltage applied. The linear variation of barrier height with the increase of DC voltage applied is confirmed experimentally. Finally, the theoretical value of averaged grain size is obtained to be 6.8 ~tm, which is almost identical to 6.5 Ixm measured from SEM images. Therefore, the macroscopic electrical properties and the microstructure can be expressed at the same time by dielectric spectra.
出处
《物理学报》
SCIE
EI
CAS
CSCD
北大核心
2012年第18期439-443,共5页
Acta Physica Sinica
基金
陕西省教育厅科研专项(批准号:12JK0434)
西安工程大学博士科研启动基金(批准号:BS0814)
国家自然科学基金(批准号:50977071
50972118)资助的课题~~
