New Members of Stuffed tridymite Structure: Synthesis, Structure, SHG, Optical and Multiferroic Properties.

We explored the stuffed tridymite structure Ba(Zn/Co) 1-x Si 1-x M 2x O 4 (M = Al 3+ and Fe 3+ ) for the possible multiferroic behaviour and to develop new inorganic colored materials. The compounds were synthesized employing conventional solid-state chemistry methods in the temperature range of 1100-1175 °C for 24 h. The powder X-ray diffraction (PXRD) and Rietveld refinement studies indicate that the compounds stabilize in P 63 space group (no. 173). The refinement results were also rationalized employing Raman spectroscopic studies.The compounds were found to be SHG active and shows a weak ferroelectric behaviour. The co-substitution of Co 2+ and Fe 3+ in the structure gives rise to a weak ferromagnetic behaviour to the compound, BaCo 0.75 Si 0.75 Fe 0.5 O 4 , making it a multiferroic material. The optical studies on the prepared compounds exhibited blue color (Co 2+ in T d geometry); purple color (Ni 2+ in T d geometry) and simultaneous substitution of Co 2+ and Fe 3+ gives rise to blue-green color due to metal-to-metal charge transfer (MMCT) effect.