Synthesis and electrical behavior study of Mn_3O_4 nanoceramic powder for low temperature NTC thermistor

摘要

Monodispersed Mn_3O_4 nanoparticles (NPs) were synthesized by reducing KMnO_4 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 disper-sity (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 ℃ with two thermistor constants (β1 = 10,897 K for 40 ℃ < T < 107 ℃and β_2 = 1,529 K for 107 ℃ < T < 190 ℃) and a negative temperature coefficient of resistance (α = -0.111 K~(-1) at 40 ℃). The thermistor constant (β_1) and NTC values are found to be higher than that of bulk Mn_3O_4 in range of 40 ℃ < T < 107 ℃. 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 ℃ and a frequency range of 1 kHz to 1 MHz delineates the role of electron hopping between Mn~(2+) and Mn~(3+) in the conduction process. These studies present monodispersed Mn_3O_4 NPs as promising material for NTC thermistor in the low temperature range 40 ℃ < T < 107 ℃.