Microwave properties of Yttrium Vanadate at cryogenic temperatures
  Yttrium Vanadate (YVO4) is a birefringent crystal material used in optical isolators and circulators with potentials for application in cryogenic microwave devices. As microwave properties of the YVO4 are not known, we measured the complex permittivity at the frequency of 25 GHz, using the Hakki-Coleman dielectric resonator technique in the temperature range from 13 K to 80 K. The real part of relative permittivity of YVO4 turned out to be similar to that of Sapphire - one of popular dielectric materials, used at microwave frequencies. The measured loss tangent tang {\delta} of the YVO4 was of the order of 10^(-6) at cryogenic temperatures. As Yttrium Vanadate (YVO4) is easy to synthesis and machine, it may replace the expensive Sapphire in some microwave applications. 
Mohan V. Jacob, Janina E. Mazierska, Jerzy Krupka, Dimitri O.   Ledenyov, Seiichi Takeuchi
cond-mat.mtrl-sci physics.ins-det