High dielectric permittivity of polyethylene oxide in humid atmospheres

Thin films (2...5 μm thickness) of polyethylene oxide (PEO) are prepared as Al-PEO-Al and Al-PEO-Si structures by a spin technique from aqueous solutions with subsequent drying at elevated temperatures. The dielectric measurements are carried out at 295 K in 6 different humidities of the atmosphere. The low frequency permittivity (22 Hz) increases from nominal ε´≈28 in 0% relative humidity (r.h.) to about 5800 in 80% r.h. The high frequency permittivity (1 MHz) is less sensitive to the humidity. In a bias field of 20 kV/cm the high permittivity can be decreased by a factor of 10 and simultaneously in triangle bias fields a hysteresis loop of the polarization appears. As a possible explanation ionic space charge effects and molecule rotation are discussed