• Ran Ran

      Articles written in Bulletin of Materials Science

    • in situ templating synthesis of conic Ba0.5Sr0.5Co0.8Fe0.2O3–𝛿 perovskite at elevated temperature

      Wei Zhou Ran Ran Zongping Shao Wanqin Jin

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      Conic Ba0.5Sr0.5Co0.8Fe0.2O3–𝛿 (BSCF) functional composite oxide was synthesized via a simple in situ templating process. The treatment of the solid precursor with concentrated nitric acid resulted in the mismatch of ionic radius at 𝐴-site and 𝐵-site of the ABO3 perovskite, due to the oxidation of cobalt/iron ions, and the formation of Ba0.5Sr0.5(NO3)2 solid solution. Therefore, instead of the direct formation of BSCF oxide, an intermediate phase of Ba0.5Sr0.5CoO3 (BSC) in hexagonal lattice structure and with conic particle shape was preferentially formed during calcination at low temperature. BSCF perovskite was then produced by the in situ templating of BSC with iron diffusing into the BSC lattice during calcination at high temperature. Wellcrystallized BSCF particles in conic shape were obtained by the calcination of the nitric acid treated precursor at 900°C.

    • Synthesis of nano-particle and highly porous conducting perovskites from simple in situ sol–gel derived carbon templating process

      Wei Zhou Ran Ran Zongping Shao Wanqin Jin Nanping Xu

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      Nano-sized La0.6Sr0.4Co0.2Fe0.8O$_{3–\delta}$ (LSCF) and La0.8Sr0.2MnO$_{3–\delta}$ (LSM) oxides were synthesized by a simple in situ sol–gel derived carbon templating process. Nano-sized LSCF–carbon and LSM–carbon composites were first obtained with a grain size of 20–30 nm. Further calcination of the obtained composites under air resulted in the nano-sized pure-phase perovskites with crystalline size of as small as 14 nm. Such a decrease in crystalline size of perovskite via the indirect calcination process was ascribed to the suppressing effect of carbon in the grain growth of perovskite. Furthermore, when the in situ created carbon was applied as a template for pore forming, a highly porous perovskite sintering body packing from the nano-sized perovskite oxide was obtained.

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