Complex Permittivity Measurements at Variable Temperatures of Low Loss   Dielectric Substrates Employing Split Post and Single Post Dielectric   Resonators
  A split post dielectric resonator in a copper enclosure and a single post dielectric resonator in a cavity with superconducting end-plates have been constructed and used for the complex permittivity measurements of single crystal substrates. (La,Sr)(Al,Ta)O3, LaAlO3, MgO and quartz substrates have been measured at temperatures from 20 K to 300 K in the split post resonator and from 15 K to 80 K in the single post resonator. The TE01delta mode resonant frequencies and unloaded Qo-factors of the empty resonators at temperature of 20 K were: 9.952 GHz and 25,000 for the split post resonator and 10.808 GHz and 240,000 for the single post resonator respectively. 
Janina E. Mazierska, Mohan V. Jacob, Dimitri O. Ledenyov, and Jerzy   Krupka
cond-mat.mtrl-sci physics.ins-det