52 巻 (2017) 2 号 p. 92-97
We have been studying the characteristics of ice as a dielectric or electrical insulation material at cryogenic temperature. IceXI, ferroelectric ice, exists at cryogenic temperature. It is very difficult to make iceXI. We applied direct-currentvoltage to ordinary ice at 253 K and cooled it to 77 K to obtain a polarized ice similar to iceXI. In this procedure, the protons move towards the cathode side under an electric field. The protons were stopped on the cathode side by cooling to 77 K, resulting in ice polarization. This polarized ice is called “ice electret”. We have previously reported the amount of electrical charge calculated from an integral of the ice electret depolarization current observed. The amount of charge increased as voltage and application time increased. In this paper, the effect of voltage, application time and temperature on depolarization current properties of the ice electret is reported. The depolarization current of the ice electret was examined in detail. Two peaks were observed in the depolarization current. One peak appeared around 270 K. But this peak did not occur in the specimen with a voltage of 140 K applied. The other peak was observed around 130 K in any specimen. The electrical charge calculated from this 130 K peak increased only when a voltage was applied, and did not increase as time and temperature increased when voltage was applied.