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Effect of Microwave-Assisted Calcination on the Phase Formation and Impedance Properties of Calcium Copper Titanate
Intelligent Manufacturing Technology Research Group, Faculty of Bioengineering and Technology, Universiti Malaysia Kelantan, Jeli Campus, 17600 Jeli, Kelantan, Malaysia
*Email Address : azwadi@umk.edu.my
Abstract : Calcium Copper Titanate (CCTO) has emerged as a highly promising electroceramic material, renowned for its colossal dielectric properties, which make it suitable for advanced applications in microelectronics and energy storage. CCTO exhibits unique properties that distinguish it as a leading electroceramic. Its colossal dielectric constant ranges from 10,000 in single crystals to 100,000 in polycrystalline forms, with stable performance over a wide temperature range (100–600 K) and frequency range (typically 1 kHz to 1 MHz). The material's high thermal stability, excellent dielectric behaviour, and ability to function in extreme conditions make it ideal for applications in capacitors, sensors, and energy storage systems. In this study, CCTO was synthesised using a microwave-assisted calcination process, wherein the effects of varying microwave irradiation times on the microstructural and dielectric properties of the material were systematically investigated. The starting materials included calcium carbonate (CaCO₃), titanium dioxide (TiO₂), and copper oxide (CuO), which were mixed in a stoichiometric ratio to achieve the desired phase composition. The synthesis process involved homogenising the raw materials through ball milling to ensure uniform mixing and reduce particle size. The mixed powders were subjected to microwave irradiation for calcination at varying durations of 1, 3, 5, 7, and 9 hours. After calcination, the powders were compacted into pellets and conventionally sintered at 1040 °C for 10 hours to achieve optimal densification and grain growth. The CCTO samples were characterised using X-ray diffraction (XRD) analysis, which confirmed the formation of the perovskite phase and revealed enhanced crystallinity with increasing microwave irradiation times. Energy-dispersive X-ray spectroscopy (EDX) verified the elemental composition and phase purity, while scanning electron microscopy (SEM) highlighted microstructural changes, including grain size evolution, bulk density improvement, and apparent porosity reduction, which were influenced by the duration of irradiation. Permittivity and dielectric loss were measured over a range of irradiation times at 1MHz, 10MHz, 100MHz, 1GHz, and 10GHz to evaluate the effects of processing conditions on the material's electrical performance, which showed that the 9 hours sample exhibited the highest dielectric constant of 2902.46 at 1 MHz, and stable response across 1 MHz–10 GHz, with low dielectric loss. The findings of this study highlight how microwave-assisted synthesis can efficiently enhance the microstructural and electrical properties of CCTO, demonstrating its potential for integration into next-generation electronic devices and energy technologies.
Keywords : calcium copper titanate, calcination, dielectric materials, microwave-assisted synthesis