CaCu_3Ti_4O_(12)陶瓷在太赫兹频段的介电特性研究

Terahertz Dielectric Properties of CaCu_3Ti_4O_(12) Ceramics

针对太赫兹（1 THz=1012Hz）电容器件发展的需求,研究了呈现巨介电和不呈现巨介电两种状态Ca Cu3Ti4O12（CCTO）陶瓷在THz波段的介电响应特性。在微波波段,小颗粒（Φ〈2μm）CCTO的介电常数εr〈700,无巨介电特征,而大颗粒（Φ〉10μm）CCTO的εr〉2000,呈现巨介电特征;两组CCTO陶瓷的介电损耗值Tanδ在0.1~0.6之间。然而,在THz波段,两种颗粒度CCTO的介电常数几乎完全相等（εr=72±3）,且损耗不超过0.18。实验结果表明,CCTO陶瓷组分的离子极化率主导了在THz波段的介电常数εr,而大颗粒CCTO对THz电磁波的散射超过小颗粒CCTO,导致介电损耗值Tanδ上升。因此,在THz波段,降低CCTO颗粒大小不会影响介电常数,反而能够降低介电损耗。这一结果表明CCTO陶瓷是制备THz波段电容的理想介电材料。

Owing to the rapid development of capacitor for terahertz（1 THz=1012Hz） electronics, the THz dielectric properties of different granular Ca Cu3Ti4O12（CCTO） ceramics are investigated experimentally. It is found that the dielectric constant εrof CCTO of small particles（Φ2 μm） is below 700, while exceeds 2000 for larger granular（Φ 10 μm） CCTO in the frequency range below 1 MHz. Correspondingly, the dielectric loss of CCTO is from 0.1 to 0.6. In THz frequency range, however, different granular CCTO ceramics exhibts the same value of εr（ εr=72±3）. The ionic polarizability dominates εr, so that it is insensitive to the grain-size of CCTO.However, the larger grain-size increases the scattering cross-section, which enlargers the total extinction ratio of transmission so as to increase the dielectric loss in THz frequency range. It is found that the small granular CCTO is a potential dielectric materials for the application of THz capacitors.