• Korean Journal of Materials Research
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• v.21 no.5
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• pp.277-282
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• 2011

Negative temperature coefficient (NTC) materials have been widely studied for industrial applications, such as sensors and temperature compensation devices. NTC thermistor thick films of $Ni_{1+x}Mn_{2-x}O_{4+{\delta}}$ (x = 0.05, 0, -0.05) were fabricated on a glass substrate using the aerosol deposition method at room temperature. Resistance verse temperature (R-T) characteristics of the as-deposited films showed that the B constant ranged from 3900 to 4200 K between $25^{\circ}C$ and $85^{\circ}C$ without heat treatment. When the film was annealed at $600^{\circ}C$ 1h, the resistivity of the film gradually decreased due to crystallization and grain growth. The resistivity and the activation energy of films annealed at $600^{\circ}C$ for 1 h were 5.203, 5.95, and 4.772 $K{\Omega}{\cdot}cm$ and 351, 326, and 299 meV for $Ni_{0.95}Mn_{2.05}O_{4+{\delta}}$, $NiMn_2O_4$, and $Ni_{1.05}Mn_{1.95}O_{4+{\delta}}$, respectively. The annealing process induced insulating $Mn_2O_3$ in the Ni deficient $Ni_{0.95}Mn_{2.05}O_{4+{\delta}}$ composition resulting in large resistivity and activation energy. Meanwhile, excess Ni in $Ni_{1.05}Mn_{1.95}O_{4+{\delta}}$ suppressed the abnormal grain growth and changed $Mn^{3+}$ to $Mn^{4+}$, giving lower resistivity and activation energy.