X-ray Diffraction Study on Restacked Flocculates from Binary Colloidal Nanosheet Systems Ti0.91O2−MnO2, Ca2Nb3O10−Ti0.91O2, and Ca2Nb3O10−MnO2

Abstract

Two-component colloidal nanosheets were prepared in Ti0.91O2−MnO2, Ca2Nb3O10−Ti0.91O2, and Ca2Nb3O10−MnO2 systems with various compositions, and were flocculated by adding K ions. X-ray powder diffraction patterns of the products showed remarkably broad reflections, and powder pattern simulation was conducted based on the matrix method for diffuse scattering from stacking disorder. An approach similar to that used for analyzing layered composite crystals with one-directional disorder was adopted for the obtained mixed-layer compounds. The structural characteristics of the restacked nanosheets in the three binary nanosheet systems were found to be dependent on the combined pairs. In the Ti0.91O2−MnO2 system, the one-dimensional solid-solution state appeared in the fairly wide composition ranges of x ≤ 0.3 and x ≥ 0.7 for xTi0.91O2−(1 − x)MnO2, and the one-dimensional two-phase stacking state appeared in the intermediate range of 0.3 < x < 0.7. In the Ca2Nb3O10−Ti0.91O2 system, the one-dimensional solid-solution state appeared in the composition ranges x ≤ 0.2 and x ≥ 0.7 for xCa2Nb3O10−(1 − x)Ti0.91O2, and the one-dimensional two-phase coexistence state appeared in the intermediate range. In the Ca2Nb3O10−MnO2 system, flocculation led to phase separation into individually restacked nanosheets, restacked K−Ca2Nb3O10 and restacked K−MnO2, throughout the composition range from 0.9Nb−0.1Mn to 0.1Nb−0.9Mn. Similarities and differences in flocculation behavior in the three binary systems, Ti0.91O2−MnO2, Ca2Nb3O10−Ti0.91O2, and Ca2Nb3O10−MnO2, were examined.