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Protonated forms of layered perovskites were derived from Aurivillius phases, Bi2ANaNb3O12 (A = Sr or Ca), 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 and electron diffraction analysis as well as by transmission electron microscopy. The compositions of the resulting products were determined to be H1.8[A0.8Bi0.2NaNb3O10] (A = Sr or Ca) by inductively coupled plasma emission spectroscopy and thermogravimetry. The acid-treated product H1.8[Sr0.8Bi0.2NaNb3O10] was capable of accommodating n-alkylamines in the interlayer space, which is in good agreement with the proposed layered structure.

An Aurivillius phase, Bi(2)SrTa(2)O(9), which consists of perovskite-like slabs and bismuth oxide sheets, was treated with 3 M hydrochloric acid for 72 h, and the resultant product was characterized. Scanning electron microscopy investigation indicated that no morphological change occurred during the acid treatment. X-ray diffraction (XRD) analysis revealed that the product exhibited tetragonal symmetry with a = 0.391 +/- 0.004 nm and c = 0.98 +/- 0.01 nm, and the a parameter is consistent with a typical value for cubic perovskite oxides. High-resolution electron microscopy (HREM) observations along both [001] and [010] showed that the structure of the perovskite-like slabs in Bi(2)SrTa(2)O(9) was retained after the acid treatment. The compositional analyses revealed the loss of a large portion of bismuth and a part of strontium (present in the bismuth oxide sheets due to B Sr disorder) and the introduction of protons. These observations indicate that the bismuth oxide sheets in Bi(2)SrTa(2)O(9) were selectively leached and that protons were introduced into the interlayer space to form a protonated layered perovskite, H(1.8)[Sr(0.8)Bi(0.2)Ta(2)O(7)]. Though diffraction techniques (XRD and electron diffraction) demonstrated that an average structure of H(1.8)[Sr(0.8)Bi(0.2)Ta(2)O(7)] consisted of perovskite-like slabs stacked without displacement, HREM observation along [010] demonstrated that both a simple stacking sequence without displacement (P-type) and a stacking sequence with a relative displacement by (a + b)/2 (I-type) were present in H(1.8)[Sr(0.8)Bi(0.2)Ta(2)O(7)].