Toshiaki Fujita

Electrical Properties of La(Cr,Mn)O3 NTC Materials

We investigated the electrical properties of the perovskite R(Cr,Mn)O3 (where R is selected from various rare earth elements and Y), which is suitable for use in negative temperature coefficient (NTC) thermistors. The substitutions of Mn for Cr in La(Cr,Mn)O3 and larger ions for R3+ decreased both the resistivities (r) and thermistor constants (B values) estimated from measurements at 25°C and 50°C according to r = r0exp(B/T). The activation energies of the carrier number (Eg) and carrier mobility (WH) were estimated by measuring the thermoelectric power and resistivity. A change in WH corresponded to a change in the B value. We discussed the relationship between the grand state electronic configuration of the M3+ ions and the local lattice distortion around the M3+ ions. The change in WH could be qualitatively linked to the M3d– O2p transfer energy, which is corresponding to the hybridization between the M3d and O2p orbital (M: transition metal elements, O: oxygen).