Dielectric properties of Ln(Mg_1/2Ti_1/2)O_3 as substrates fOr high-T. superconductor thin films

摘要

Ln(Mg_1/2Ti_1/2)O_3(Ln = Dy, La, Nd, Pr, Sm, Y) compositions have been prepared, and their pertinent properties for use as thin film substrates for YBa_2Cu_3O. (YBCO) were measured. X-ray diffraction shows that Ln(Mg_l/2Ti_l/2)O_3 compositions have noncubic symmetry and the GdFeO_3-type structure. Dielectric constant measurements revealed values between 22 and 27, which are larger than those of the LnAlO_3 family. Quality factor (= 1/ tan δ) of the ceramic specimens measured at room temperature was larger than 3000 at 10 GHz. Among the compounds, Ln(Mg_1/2Ti_1/2)O_3 exhibited the highest dielectric constant and the lowest dielectric loss. Chemical reaction was observed between Ln(Mg_1/2Ti_1/2)O_3 (Ln = Dy, Sm, Y) and YBCO after annealing a 1 : 1 mixture at 950 deg. C. Considering dielectric and physical properties,Ln(Mg_1/2Ti_1/2)O_3 and Sm(Mg_1/2Ti_1/2)O_3 were determined to be suitable substrates for YBCO thin film used in microwave applications.