Ten-fold tunability of the permittivity of Ba/sub 1-x/Sr/sub x/TiO/sub 3/ in epitaxial multilayers with (Y/Nd)Ba/sub 2/Cu/sub 3/O/sub 7-/spl delta//

Dielectric properties of 400-600 nm thick epitaxial layers of SrTiO/sub 3/ and Ba/sub 0.9/Sr/sub 0.1/TiO/sub 3/, inserted between YBa/sub 2/Cu/sub 3/O/sub 7-/spl delta// or NdBa/sub 2/Cu/sub 3/O/sub 7-/spl delta// electrodes, were investigated as functions of temperature and electric field. The electric field response of the dielectric permittivity of the ferroelectric layer correlated with the Curie point and was considerably higher with Nd based than with Y based superconducting electrodes. Insertion of thin buffer layers improved the tunability and decreased the microwave losses of the Ba doped dielectric.