Open Access Research Article Issue
CaTiO3 nano ceramic for NTCR thermistor based sensor application
Journal of Advanced Ceramics 2014, 3 (2): 117-124
Published: 01 June 2014

It is possible to fabricate highly sensitive NTCR (negative temperature coefficient of resistance) thermistor using nano crystalline CaTiO3 synthesized by high energy ball milling. Disc shaped green pellets were prepared and effects of sintering on the disc pellets were studied as thermistor by sintering the samples at 1000 ℃, 1100 ℃ and 1200 ℃. The as-prepared samples were characterized by X-ray diffraction (XRD), impedance analysis and electrical measurement. The resistivity of the prepared samples varies predictably with temperature: this makes them promising material for temperature sensor. The experimental results prove that nano crystalline CaTiO3 ceramic is one kind of thermistor with exponential negative temperature coefficient of resistance in the temperature range of 300–500 ℃. The samples have the advantages of rapid response, high sensitivity and capability to withstand thermal surges over the temperature range of 300–500 ℃. Resistance–temperature characteristics are described by thermistor equation with thermistor constant around 4003 K to 10795 K and thermal coefficient of resistance α around -1%/℃ to -13%/℃. The activation energy is in the range of 0.34–0.93 eV. The observed thermistor parameters are found to be comparable with many of the known thermistor materials. This suggests that the electrical properties can be adjusted to desirable values by controlling the temperature parameter. The influence of fabrication process of disc thermistor and electrical properties are discussed. The study shows the potential of nano crystalline CaTiO3 to act as an NTCR material for thermistor applications.

Open Access Research Article Issue
Frequency and temperature dependent electrical characteristics of CaTiO3 nano-ceramic prepared by high-energy ball milling
Journal of Advanced Ceramics 2013, 2 (3): 291-300
Published: 07 September 2013

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.

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