Synthesis and characterization of strontium and calcium titanate polycrystalline powders by a modified polymeric precursor technique

SrTi0,65Fe0,35O3-delta, Ca0,5Sr0,5Ti0,65Fe0,35O3-delta, CaTi0,65Fe0,35O3-delta ceramic powders were synthesized by the polymeric precursor technique using CaCO3, SrCO3, C12H28O4Ti and Fe(NO3)(3.9)H2O. After calcination, each powder was heat treated at temperatures chosen according to data collected on thermogravimetric-differential thermal analysis experiments. The compositions were analyzed by X-ray diffraction for structural phase evaluation (either perovskite cubic or orthorhombic), laser scattering for determination of particle size distribution and average particle size, transmission electron microscopy (TEM) for observation of particle shape and average true size. Pressed powders sintered at 1250 degrees C were analyzed by X-ray diffraction and X-ray fluorescence; their surfaces were observed by scanning probe microscopy (SPM) for topographical analysis of grains and grain boundaries. TEM results show that the powders consist of agglomerated nanoparticles. Sr-based compounds have cubic perovskite phases whereas Ca-based compounds are orthorhombic. SPM images show intergranular features which might be responsible for reported blocking of charge carriers observed in impedance spectroscopy diagrams.