针对太赫兹(1 THz=1012 Hz)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CaCu3Ti4O12(CCTO)陶瓷在THz波段的介电响应特性。在微波波段，小颗粒(Φ<2 μm)CCTO 的介电常数εr＜700，无巨介电特征，而大颗粒(Φ>10 μm)CCTO 的εr＞2000，呈现巨介电特征；两组CCTO 陶瓷的介电损耗值Tan δ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Tan δ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=1012 Hz) electronics, the THz dielectric properties of different granular CaCu3Ti4O12 (CCTO) ceramics are investigated experimentally. It is found that the dielectric constant ε r of CCTO of small particles (Φ＜2 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.