Using rf cathode sputtering in an oxygen atmosphere, we produced a heterostructure based on the bismuth ferrite (BFO) multiferroic and barium strontium niobate (SBN) ferroelectric: BiFeO3(1000 nm)/Sr0.5Ba0.5Nb2O6(1000 nm)/Pt(001)/MgO(001). It was free of impurity phases and had a root mean square surface roughness within 1% of its thickness. All of the layers in the heterostructure were grown epitaxially. The SBN-50 layer consisted of orientation domains tilted in the plane of the interface by ±18.4° with respect to the MgO substrate axes, and the crystallographic axes of the BFO and Pt layers were parallel to the substrate axes. The ferroelectric polarization of the material at U = 90 V was shown to be 59.3 μC/cm2. Our results demonstrate that, to describe the behavior of the relative dielectric permittivity (ε) of the heterostructure in the range 25–250°C, it is sufficient to take into account the ε(t) data for each layer. The mechanisms underlying the observed effects are discussed.