The Effect of 0.15 and 0.30 mol CuO Additions on the Electrical Properties of Nickel Manganite-based NTC Thermistors

A decrease in electrical resistance with increasing temperature is the characteristic feature of NTC thermistor utilized as temperature sensors in industrial applications. Nickel manganite is used as one of the main compositions for application of NTC thermistors. The electrical properties of nickel manganite based NTC thermistors are altered by the addition of additives such as cobalt oxide, iron oxide, chromium oxide and copper oxide etc. In this study; the effect of copper oxide addition on the electrical and microstructure properties of nickel manganite based NTC thermistors were investigated. For this purpose, Ni0.5 Co0.5CuxMn2-xO4 (x=0.15 and 0.30) samples were prepared by conventional ceramic processing techniques. The samples were sintered at 1300 ˚C for 5 hours. The addition of CuO plays an important role by increasing the bulk density, improving the microstructure properties and enhancing the electrical characteristics of NTC thermistors. It was determined that the relative bulk density of samples was ~97 %. The electrical resistivity (ρ) and material constant ( B ) of Ni0.5 Co0.5 Cu0.15Mn1.85O4 sample were determined as 286 Ω.cm and 3355 K. The values of electrical resistivity and material constant decreased with increasing CuO content. The electrical resistivity and material constant of Ni0.5Co0.5Cu0.3Mn1.7O4 sample were calculated as 61 Ω.cm and 3124 K.