The dielectric properties of barium titanate at low temperatures

[摘要] Measurements of the complex dielectric constant of ceramic barium titanate have been made at temperatures ranging from 300°K down to 2.4°K. The frequencies employed ranged from 50 kilocycles per second up to 2 megacycles per second with the majority of the measurements at 500 kilocycles per second. The real part of the dielectric constant, K ;;, had a value of about 1100 at room temperature, decreasing to approximately 100 in the liquid helium temperature region (2--4°K). The slope of K;; against the temperature had a high positive value of 0.01 per °K in agreement with Wul. The imaginary part of the dielectric constant, K″, had a value of about 4 at room temperature, rising to a very broad maximum of approximately 15 at 200°K and steadily decreasing below 80°K to room temperature values below 4 in the liquid helium region. The experimental work was done in the Collins cryostat of the low temperature laboratory of The Rice Institute, and the impedance measurements were made with a Boonton Q-meter and a General Radio Type 916-A impedance bridge. In addition to the pure barium titanate measurements, measurements were also made on specimens diluted with 15% and 30% strontium titanate respectively. The curves obtained for diluted specimens had the same general appearance as those for the pure barium titanate except that the sharp maximum in the K;; curve, normally occurring at 390°K, was brought near room temperature in case of the 15% dilution and to 274°K for the 30% dilution. This lowering of the temperature of the peak is in accord with results reported by von Hipple, Coursey and Brand, and Jackson and Reddish.

[发布机构] Rice University