Humidity sensitive properties of pure and Mg-doped CaCu3Ti4O12

CaCu3Ti4O12 (CCTO) is known as a dielectric material exhibiting a high and relatively temperature-independent dielectric constant over a wide temperature range from 100 to 400 K. Here, we report the huge responses of dielectric constant to relative humidity found in ceramic CCTO and Mg-doped CCTO. The dielectric constant at 97% relative humidity is about 5.8 times larger than that at 11% relative humidity for pure CCTO measured at 1 kHz. Mg doping enhances the sensitivity of dielectric constant to relative humidity. CCTO and Mg-doped CCTO are promising candidates for fabricating new humidity sensors.