Structure and ferroelectric properties of BaBi3.8M0.2(Ti3.8Nb0.2)O15 (M=Mg, Ca, Sr and Ba) ceramics

Bismuth layer structured compounds BaBi3.8M0.2(Ti3.8Nb0.2)O15, with M=Mg, Ca, Sr and Ba, were synthesized through a modified chemical route. Phase and structure of the compounds were analyzed by X-ray diffraction. The structure of Mg2+ based compound was orthorhombic, while it was tetragonal for the other three compositions. Experimental results indicate that Mg2+ prefers to substitute in the Bi2O2 layer. The room temperature permittivity was maximum for Ba2+ based compound (∼432). The piezoelectric coefficient was significantly enhanced in Mg2+ based compound. The Curie temperature was found to decrease gradually in the order Mg>Ca>Sr>Ba based compound. There was a marked improvement in the relaxor behavior and remnant polarization for Ba2+ based compound. The structural changes and dielectric, ferroelectric and piezoelectric properties of all the compounds was discussed and co-related.