Synthesis of platelike CaTiO 3 particles by a topochemical microcrystal conversion method and fabrication of textured microwave dielectric ceramics

Abstract

Platelike CaTiO 3 particles with an orthorhombic perovskite structure have been synthesized by topochemical microcrystal conversion (TMC) from platelike precursor particles of the layer-structured CaBi 4Ti 4O 15 at 950 °C. The CaTiO 3 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 CaBi 4Ti 4O 15 is converted into the {1 0 0} plane of CaTiO 3. Using the platelike CaTiO 3 particles as templates in the templated grain growth method, dense {1 0 0} grain-oriented CaTiO 3 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 Q f value of 9310 GHz in textured ceramics compared to that of 6005 GHz in non-textured ceramics.