Dielectric constant studies of insulating Y2BaCuO5

This paper reports on the dielectric constant of Y2BaCuO5 from 100 Hz to 20 GHz for temperature from 300 K down to 20 K. At room temperature and below 10 kHz, it varies strongly with frequency, but remains nearly constant at 3.7 from 10 kHz up to 20 GHz. It decreases with decreasing temperature from 300 K. Below 120 K, it saturates to 3.4, which is the lowest dielectric constant among the materials known to date except for some organic materials. The dissipation factor for the authors' pure sample becomes less than the resolution limits of the authors' apparatus for frequency from 1 MHz to 20 GHz