Abstract
Nanocrystalline calcium titanate (CT) ceramic has been synthesized by a combination of solid-state reaction and high-energy ball milling. This nano-ceramic is characterized by X-ray diffraction (XRD), dielectric study and impedance spectroscopy. The XRD pattern shows single phase ceramic of orthorhombic symmetry. The frequency-dependent dielectric study shows that the dielectric constant is maximized at low frequencies and decreases with an increase in frequency. Impedance spectroscopy analyses reveal a non-Debye type relaxation phenomenon. A significant shift in impedance loss peaks toward the higher-frequency side indicates conduction in the material favoring the long-range motion of mobile charge carriers. The grain conduction effect is observed from the complex impedance spectrum by the appearance of one semicircular arc in Nyquist plot. It is also observed that the resistance decreases with an increase in temperature showing a negative temperature coefficient of resistance (NTCR). Various thermistor parameters have been calculated by fitting with Steinhart-Hart equation. The modulus plots represent the presence of temperature- dependent electrical relaxation phenomenon with the material. The frequency-dependent AC conductivity at different temperatures indicates that the conduction process is thermally activated. The activation energy has been calculated from an Arrhenius plot of DC conductivity and relaxation frequency.
Highlights
CaTiO3 (CT) belongs to the important group of compounds with a perovskite-type structure which has been widely used in electronic devices, and it is a key component of synroc [1]
Nanocrystalline calcium titanate ceramic has been prepared by a high-energy ball milling technique
The temperature-dependent dielectric study reveals a normal ferroelectric behavior in the material. Electrical parameters such as the real part of impedance ( Z ), the imaginary part of impedance ( Z ) and AC/DC conductivity as functions of both frequency and temperature have been studied through impedance spectroscopy
Summary
CaTiO3 (CT) belongs to the important group of compounds with a perovskite-type structure which has been widely used in electronic devices, and it is a key component of synroc (a type of synthetic rock used to store nuclear waste) [1] It has high dielectric constant, low dielectric loss and large temperature coefficient of. It has been noticed that the size reduction process and the microstructural evolution of CaTiO3 during milling process are mainly influenced by the type of impulsive stress applied by the grinding media, which can either be an impact or shear type. Other parameters such as atmosphere composition and presence of different liquid media inside the grinding mill affect the mechanochemical process. The aim of this work, is to give an additional contribution in understanding the mechanochemical synthesis of CaTiO3 nanoparticles without the deleterious phase and to study their electrical behavior via impedance and dielectric investigation
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