Reactive-sintering of Ba_0.5Sr_0.5Co_0.8Fe_0.2O_3−δ using alkaline earth peroxides for low-temperature synthesis

Abstract

In this study, we developed the low-temperature synthesis of Ba_0.5Sr_0.5Co_0.8Fe_0.2O_3−δ (BSCF) using barium peroxide (BaO₂) and strontium peroxide (SrO₂) as starting materials of A-site elements in perovskite. The sintered bodies were obtained at a low temperature of 700°C by two approaches. One was a two-step sintering process, which included the preparation of fine hexagonal-phase BSCF powders with mean crystallite sizes of 20–30 nm by a novel low-temperature solid-state reaction before sintering. Another approach was a one-step sintering process using reactive sintering, which is the simultaneous reaction of BSCF synthesis and green body sintering from the starting material powders. For the sintered bodies obtained by the one- and two-step sintering processes, the relative density was ca. 50%. The reactive-sintered body of hexagonal-phase BSCF obtained by the one-step process showed higher electrical conductivity of 6.3 S cm⁻¹ at 500°C than the BSCF sintered bodies obtained by the two-step process (4.1 S cm⁻¹). Reactive sintering realizes good connectivity among BSCF particles, which enhances the electrical conductivity of porous BSCF bodies.