Synthesis of Ba2TiOSi2O7 and Ba2TiOSi1.8Ge0.2O7 ferroelectric ceramics and the structure determination by Rietveld analysis

Polycrystalline ceramic samples of pure fresnoite compound of formula Ba₂TiOSi₂O₇ and germanium (Ge⁴⁺) doped compound Ba₂TiOSi_1.8Ge_0.2O₇ have been prepared by standard solid state reaction technique using high purity oxides and carbonates. The pure compound of fresnoite was sintered at 1300 °C while the Ge⁴⁺ substituted compound was sintered into pellet form at 1180 °C. The formation of the single phase compound was confirmed by X-ray diffraction (XRD) and the structural parameters were refined by the Rietveld analysis. A good agreement between observed and calculated X-ray diffraction pattern was obtained from the Rietveld refinement using noncentrosymmetric space group P4bm. The bond distances along with bond angles between atoms for both the compounds as well as the position of the atoms in the unit cell were calculated which supports the structural results. The grain size of both the compounds was investigated from SEM micrographs. The results are discussed in detail.