Synthesis of platelike CaTiO3 particles by a topochemical microcrystal conversion method and fabrication of textured microwave dielectric ceramics

Platelike CaTiO3 particles with an orthorhombic perovskite structure have been synthesized by topochemical microcrystal conversion (TMC) from platelike precursor particles of the layer-structured CaBi4Ti4O15 at 950 °C. The CaTiO3 particles inherited and retained the shape of the precursor particles with a thickness of approximately 0.3 μm, and a width of 2–6 μm. XRD analysis showed that in the TMC reaction, the crystallographic {0 0 1} plane of CaBi4Ti4O15 is converted into the {1 0 0} plane of CaTiO3. Using the platelike CaTiO3 particles as templates in the templated grain growth method, dense {1 0 0} grain-oriented CaTiO3 ceramics having a {1 0 0} orientation could be fabricated at sintering temperatures between 1350 and 1500 °C. The maximum orientation factor reached 99.7% at 10% of template. It was found that texturing improves microwave dielectric low-loss properties, providing a 1.55 times higher Qf value of 9310 GHz in textured ceramics compared to that of 6005 GHz in non-textured ceramics.