Sol-gel synthesis of complex metal oxides with double and triple perovskite-type structure

Abstract

Perovskit je naziv za porodicu spojeva kristalne strukture čija je opća formula ABX3 gdje je A kation većeg ionskog promjera, B kation manjeg ionskog promjera, a X halogenidni anion ili kisik. U ovome diplomskom radu citratnom dvostupanjskom sol – gel metodom sintetizirani su sloţeni metalni oksidi perovskitne strukture $Sr_{3}Co_{2}TeO_{9}$, $Ba_{3}Co_{2}TeO_{9}$, $Sr_{3}NiTeO_{6}$ te $Ba_{2}NiTeO_{6}$. Nakon prvostupanjskog miješanja prekursora i kompleksacije citratnom kiselinom, u drugom koraku su osušeni uzorci kalcinirani pri 600 ˚C i 1000 ˚C u peći u struji zraka s temperaturom zagrijavanja 2 ˚C/min. Uzorci su karakterizirani cikličkom voltametrijom, infracrvenom spektroskopijom (FT – IR), termogravimetrijskom analizom (TGA), rentgenskom difrakcijom na prahu (PXRD) te su im odreĎena magnetska svojstva SQUID mjerenjima. UtvrĎeno je da su sintetizirani spojevi visoke čistoće te da su veličine kristalita male unatoč visokim temperaturama kalciniranja. $Sr_{3}NiTeO_{6}$ i $Ba_{2}NiTeO_{6}$ pokazuju antiferomagnetska svojstva.Perovskite is the name for a family of compounds with crystal structure of the general formula ABX3 where A is a cation of a larger ionic radius, B is a cation of a smaller ionic radius and X stands for halide or oxide anion. In this diploma thesis, complex metal oxides of perovskite type crystal structure $Sr_{3}Co_{2}TeO_{9}$, $Ba_{3}Co_{2}TeO_{9}$, $Sr_{3}NiTeO_{6}$ and $Ba_{2}NiTeO_{6}$ were synthesized by the citrate sol - gel route. Dried samples were calcined at 600 °C and 1000 °C in a furnace with air flow and at a temperature rate of 2 °C per minute. Samples were characterized by the cyclic voltammetry, infrared spectroscopy (FT –IR), thermogravimetric analysis (TGA), Powder X – ray diffraction (PXRD) while magnetic ground state has been determined using SQUID measurement. Obtained results have revealed that synthesized materials are of high purity and their average crystallite size has remained in nanometer range despite the high calcination temperatures. $Sr_{3}NiTeO_{6}$ and $Ba_{2}NiTeO_{6}$ posses antiferromagnetic properties