Influence of Fe–F-co-doping on the dielectric properties of Ba0.6Sr0.4TiO3 thick-films

Abstract The influence of Fe acceptor and Fe – F acceptor – donor co-doping on the dielectric response of screen-printed Ba0.6 Sr0.4 TiO3 thick-films on alumina substrates has been investigated. The Ba0.6 Sr0.4 TiO3 powders were synthesized by freeze-drying of sols. Permittivity, dielectric loss, and tunability were investigated at kHz frequencies with a planar metal-insulator-metal capacitor structure, and at GHz frequencies up to 40 GHz using coplanar waveguide structures. Pure acceptor doping by Fe was found to have a distinct influence on permittivity and dielectric loss-factor at kHz-frequencies and at GHz frequencies due to an internal bias field and pairs of associated defects. Co-doping with F significantly suppresses the influence of the internal bias field and defect-associates at low and microwave frequencies. The commutation quality factor at 10 GHz and Eeff = 5.8 V μm-1 was increased by co-doping the thick-films with Fe and F. Such doped Ba0.6 Sr0.4 TiO3 films show a high potential for tunable microwave applications.

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