Synthesis of Mn-bearing Layered Perovskite-type Niobate and Its Delaminated Nanosheet

Abstract

Layered perovskite-type compounds with the general formula MCa₂MnNb₃TiO₁₃ (M = K, Rb), in which Mn²⁺ is incorporated into the A-site of the perovskite layers, were synthesized via a unique conventional solid-state reaction. The synthesis was conducted by thoroughly mixing a layered perovskite precursor, MCa₂Nb₃O₁₀, with ilmenite-type MnTiO₃ in a stoichiometric molar ratio, followed by high-temperature calcination at 1473 K. Compositional and structural characterizations involving elemental analysis and Rietveld refinement confirmed that the perovskite slabs in the host layers are four [Nb,Ti]O₆ octahedra thick, with Ca²⁺ and Mn²⁺ ions occupying the A-sites. Ion exchange treatment with an acid solution effectively replaced the interlayer alkali metal ions (K⁺ or Rb⁺) with protons. Subsequent exfoliation by shaking in an aqueous tetrabutylammonium hydroxide solution yielded a light brown suspension. The colloidal material dispersed was deposited onto a Si substrate surface. Atomic force microscopy (AFM) revealed the presence of numerous micrometersized 2D nanosheets with a uniform thickness of approximately 2.0 nm, indicating complete exfoliation into single perovskite layers. Further in-depth analysis via in-plane and out-of-plane X-ray diffraction (XRD), as well as X-ray photoelectron spectroscopy (XPS), confirmed that the obtained 2D materials correspond to individual perovskite layers derived from the Mn-substituted parent phase.