Optical response of high-dielectric-constant perovskite-related oxide
Optical response of high-dielectric-constant perovskite-related oxide
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DOI：
10.1126/science.1061655
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发表时间：
2001-07-27
期刊：
影响因子：
56.9
通讯作者：
Ramirez, AP
中科院分区：
文献类型：
--
作者：
Homes, CC;Vogt, T;Ramirez, AP
对钙钛矿相关氧化物CaCu3Ti4O12的光学电导测量提供了这种材料中观察到的巨介电效应背后的物理线索。低频振动表现出反常的行为，这意味着在低温下单位电池内存在电荷的重新分布。在红外频率(太赫兹)下，室温下的介电常数值类似于80，这比在较低无线电频率(千赫兹)下获得的类似于10(5)的值要大得多。这种差异意味着，由于偶极弛豫，在两个频率处都存在强吸收。在室温下，特征弛豫时间很快(小于或接近500纳秒)，但在两个温度下，特征弛豫时间急剧增加，这表明介电常数的较大变化可能是由于纳米尺度磁区中偶极涨落的松弛动力学抑制。
Optical conductivity measurements on the perovskite-related oxide CaCu3Ti4O12 provide a hint of the physics underlying the observed giant dielectric effect in this material. A low-frequency vibration displays anomalous behavior, implying that there is a redistribution of charge within the unit cell at low temperature. At infrared frequencies (terahertz), the value for the dielectric constant is similar to 80 at room temperature, which is far smatter than the value of similar to 10(5) obtained at lower radio frequencies (kilohertz). This discrepancy implies the presence of a strong absorption at very tow frequencies due to dipole relaxation. At room temperature, the characteristic relaxation times are fast (less than or similar to 500 nanoseconds) but increase dramatically at tow temperature, suggesting that the large change in dielectric constant may be due to a relaxor-like dynamical stowing down of dipolar fluctuations in nanosize domains.