Development of solvent-free synthesis using planetary ball mill for CaFe systems of complex metal oxides

Abstract

Perovskiti su spojevi opće formule ABX3 gdje je A kation većeg ionskog promjera, B kation manjeg ionskog promjera, a X kisikov ili halogenidni anion. U ovom su radu istraživani optimalni uvjeti za sintezu trostrukog perovskita $Ca_{3}Fe_{2}WO_{9}$ sintetskom metodom bez otapala uz pomoć planetarog kugličnog mlina. Pri tomu za kation na A položaju odabran je $Ca^{2+}$, B položaj dijele $Fe^{3+}$ i $WO^{6+}$ u omjeru 2:1, a na anionskom položaju nalazi se kisik Parametri koji su mijenjani s ciljem poboljšanja sintetskih uvjeta su brzina vrtnje mlina (100, 150, 200, 250, 500 i 750 okr/min) te vrijeme sinteze u razmacima od 10 min do ukupno 120 min. Dobiveni uzorci su kalcinirani na različitim temperaturama te analizirani termogravimetrijski (TGA), infracrvenom spektroskopijom (FT-IR) i rentgenskom difrakcijom na prahu (PXRD). Produkt sintetiziran pri 250 okr/min i vremenu od 10 minuta imao je najveći udio ciljanog spoja, čak 92 wt %. Veličina kristalita izračunata preko Scherrerove jednadžbe je iznosila 24 nm. Ciljani $Ca_{3}Fe_{2}WO_{9}$ je po prvi put sintetiziran u nanokristalitnom obliku.Perovskites are compounds of general formula ABX3 where A is a cation of a larger ionic diameter, B is a cation of a smaller ionic diameter and X stands for oxygen or halide anions. In this thesis optimal conditions for a synthesis of a triple perovskite $Ca_{3}Fe_{2}WO_{9}$ using solvent-free method by means of planetary ball mill were investigated. As it can be seen, as A site cation $Ca^{2+}$ was chosen, $Fe^{3+}$ and $WO^{6+}$ share the B site in 2:1 ratio and oxygen anion was chosen for anionic site. Parameters which have been varied in the attempt to optimize synthesis conditions are rotational speed (100, 150, 200, 250, 500 and 750 rpm) and synthesis time in intervals of 10 minutes up to 120 minutes. Obtained samples were calcined at different temperatures and analyzed by thermogravimetric analysis (TGA), infrared spectroscopy (FT-IR) and powder X-ray diffraction (PXRD). Product synthesized at 250 rpm for 10 minutes contained 92 wt% of the targeted compound. Crystallite size calculated from the Scherrer equation was 24 nm. Targeted $Ca_{3}Fe_{2}WO_{9}$ has been synthesized in nanocrystalline form for the first time