Study on the conduction mechanism and performance of LaCr0.7Fe0.3O3-BaTiO3 ceramics as wide-temperature-range NTC thermistor materials

Abstract

In this work, xLaCr_0.7Fe_0.3O₃-(1-x)BaTiO₃ (xLCF-BT, x = 0.05, 0.10, 0.15, and 0.20) ceramics were prepared via the solid-phase synthesis. The study found that all samples exhibited the single perovskite structure, and the addition of LCF reduced the grain size and bandgap of the ceramics. All ceramic samples have a negative temperature coefficient (NTC) effect, as the LCF content increased, the resistivity ρ₃₀₀ decreased from 2.32 × 10⁷ to 1.04 × 10⁵ Ω•cm, while thermal constant B_300/500 varied between 6673 and 11398 K. In situ XPS analysis revealed that conduction in xLCF-BT ceramics involves electron hopping between heterovalent ion pairs (Cr³⁺/Cr⁴⁺ and Fe²⁺/Fe³⁺), with the NTC effect originating from increased electron hopping probability at elevated temperatures. Impedance analysis showed that the electrical inhomogeneity originated from grains and grain boundaries, and both grains and grain boundaries contributed to the NTC effect. Moreover, all ceramics exhibit good stability, showing resistance drift below 3.45%. These findings establish the LCF-BT system as a promising candidate for wide-temperature-range NTC thermistors and related applications.