RELATIVE PERMITTIVITY AND DIELECTRIC LOSS TANGENT OF SUBSTRATE MATERIALS FOR HIGH-TC SUPERCONDUCTING FILM

We measure the relative permittivity epsilon-r and dielectric loss tangent tan-delta of substrate materials for high-T(c) superconducting films at 18-300 K and at 5-10 GHz using the cavity-resonator method. The materials measured are single crystals of MgO, LaAlO3, YAlO3, LaSrGaO4, NdGaO3, sapphire, and ZrO2 ceramic. The epsilon-r values are 10-30 and become almost constant below about 50 K. The tan-delta values decrease with decreasing temperature and are below 1 x 10(-5) at 77 K except for those of NdGaO3 and ZrO2 ceramic. This suggests that the tan-delta values of MgO, LaAlO3, YalO3, LaSrGaO4, and sapphire do not limit the quality factors of microwave passive components fabricated using high-T(c) superconducting films. It is also demonstrated that the tan delta of the substrate material is strongly affected by impurities.