Synthesis and electrical behavior study of Mn3O4 nanoceramic powder for low temperature NTC thermistor
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Monodispersed Mn3O4 nanoparticles (NPs) were synthesized by reducing KMnO4 at room temperature in the presence of cetyltetrabutylammonium bromide surfactant and short chain tetra-n-butylammonium bromide co-surfactant. Structural characterization done through XRD, TEM and FT-IR analysis techniques showed mono dispersity (5–8 nm) and capping of the NPs with surfactants. The temperature dependent behavior of dc resistivity of the nanopowder pellets showed reproducible NTC characteristics over a range of 40–200 °C with two thermistor constants (β1 = 10,897 K for 40 °C < T < 107 °C and β2 = 1,529 K for 107 °C < T < 190 °C) and a negative temperature co-efficient of resistance (α = −0.111 K−1 at 40 °C). The thermistor constant (β1) and NTC values are found to be higher than that of bulk Mn3O4 in range of 40 °C < T < 107 °C. This observed behavior implies an enhanced sensitivity in nano-powder based thermistors. Temperature and frequency dependent impedance behavior of the as-synthesized samples evaluated over a temperature range of 40–140 °C and a frequency range of 1 kHz to 1 MHz delineates the role of electron hopping between Mn2+ and Mn3+ in the conduction process. These studies present monodispersed Mn3O4 NPs as promising material for NTC thermistor in the low temperature range 40 °C < T < 107 °C.
KeywordsMn3O4 TBAB Negative Temperature Coefficient Thermistor Constant Hydrazine Monohydrate
The authors are thankful to Dr. Pawan Kapur, Director, CSIO (CSIR) for permitting us to carry out these studies. The authors are also thankful to Dr. Tripathi (Physic Department, Punjab University), Mamta Sharma, and Dr. Akashdeep (CSIO) for their timely contributions in experimental work, valuable inputs and suggestions.
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