Studies of Structure, Dielectric, and Electrical Properties of MgCaFeNbO 6 Ceramic for NTC Thermistor Application

In this paper, a double perovskite MgCaFeNbO6 ceramic was synthesized and systematically investigated to evaluate its potential for negative temperature coefficient (NTC) thermistor applications. The FullProf Rietveld structural analysis performed using recorded X-ray diffraction (XRD) data to confirm the formation of a monoclinic crystal symmetry with. average crystallite size of 108.3 ± 1.7 nm, and the corresponding microstrain was (6.20 ± 0.25) × 10−5 along with dislocation density 8.52 × 1013 m−2. Study of dielectric constant and loss with both frequency and temperature reveals that sample attains maximum dielectric constant of 1125 and loss of 0.4, indicating good quality material for energy storage devices. Study of impedance with frequency reveals a typical negative temperature coefficient of temperature (NTCR) character, decreasing resistance part with increasing temperature. The calculated activation energy values suggested strong thermally activated conduction, dominated by small polaron hopping of localized charge carriers between Fe2+/Fe³+ and Nb4+/Nb5+ ions. The study of the electrical modulus versus frequency confirms the presence of a non-Debye type of relaxation. The analysis of both Nyquist and Cole-Cole plots reveals that the studied sample has semiconducting properties and restricted application related to semiconductors. The study of resistance versus temperature provides thermistor constant, sensitivity factor, and activation energy values that fall within the range suitable for practical NTC thermistor applications.