Synthesis and characterization of a new four-layer Aurivillius phase Bi2SrNa2Nb4O15 and its protonated form

A new four-layer Aurivillius phase Bi2SrNa2Nb4O15 has been synthesized by solid-state reaction of Bi2SrNb2O9 and NaNbO3 at 1100 °C. The detailed structure determination of Bi2SrNa2Nb4O15 performed by powder X-ray diffraction (XRD) shows that it crystallizes in the space group I4/mmm [a∼3.9021(1) Å, c∼40.7554(10) Å]. Protonated form of Bi2SrNa2Nb4O15 was obtained by the substitution of bismuth oxide sheets with protons via acid treatment. The conversion into the protonated forms was achieved easily using 6 M HCl at room temperature. Preservation of the structure of the perovskite-like slabs and contraction in the c-axis were confirmed by X-ray analysis. The compositions of the resulting products were determined to be H1.8[Sr0.8Bi0.2Na2Nb4O13] by X-ray fluorescence spectroscopy (XFS) and thermogravimetry.