Hydrothermal synthesis of perovskite CaTiO3 tetragonal microrods with vertical V-type holes along the [010] direction

Abstract

Single-crystalline perovskite CaTiO₃ tetragonal microrods with vertical V-type holes along the [010] direction have been successfully synthesized by employing layered K₂Ti₆O₁₃ nanofibers as titanate sources via a conventional hydrothermal route. The as-prepared CaTiO₃ tetragonal microrods with vertical V-type holes were characterized by means of X-ray diffraction, field-emission scanning electron microscopy, transmission electron microscopy (TEM), high-resolution TEM and selected area electron diffraction. In order to understand the formation mechanism of the CaTiO₃ tetragonal microrods with vertical V-type holes, a series of KOH concentration- and time-dependent experiments were carried out. Generally, low KOH concentrations lead to slow formation of calcium titanate species and a subsequent mild crystallization to CaTiO₃ perovskite. Moreover, the dehydration and condensation of the K₂Ti₆O₁₃ nanofibers and Ca(OH)₂ precipitates for the calcium titanate species lead to a Ca²⁺ ion substitution for K⁺ ions in the lattice of the layered K₂Ti₆O₁₃ nanofibers. In consequence, some K₂Ti₆O₁₃ nanofibers are embedded in the originally formed CaTiO₃ tetragonal particles and the single-crystalline perovskite CaTiO₃ tetragonal microrods with vertical V-type holes along the [010] direction are derived by the dissolution of the embedded K₂Ti₆O₁₃ nanofibers at a moderately low KOH concentration of ca. 1.0 mol L⁻¹.