Research on the electrical and aging properties of NixMn1.13-xCo0.74Fe1.13O4 thermistor ceramics

The stability of thermistors determines the precision and reliability of the electronics, representing a critical constraint for high-precision applications. This study investigates spinel- structured Ni_xMn_1.13-xCo_0.74Fe_1.13O₄ (x = 0.12, 0.18, 0.24, 0.30 and 0.36) NTC thermistor ceramics, systematically examining the effects of Ni/Mn ratio, sintering process, and annealing treatment on the electrical and aging characteristics. Experimental results show that increasing Ni doping content (x) promotes preferential occupation of Ni²⁺ at octahedral B-sites, driving the oxidation of Mn³⁺ to Mn⁴⁺ for charge balance compensation, thereby significantly reducing room-temperature resistivity from 3.75 × 10⁶ Ω·cm to 2.11 × 10⁴ Ω·cm. Optimal aging resistance (4.42%) was achieved at x = 0.18. Sintering temperature studies revealed that samples processed at 1180 °C for 4 h exhibited superior comprehensive performance: material constant B reached 3829.24 K with resistivity of 2.45 × 10⁶ Ω·cm and aging rate of 4.46%. Further annealing treatment (860–1100 °C) of Ni_0.18Mn_0.95Co_0.74Fe_1.13O₄ ceramics sintered at 1180 °C effectively reduced oxygen vacancy concentration, decreasing the aging rate to 0.81% while maintaining excellent electrical properties (ρ = 4.35 × 10⁴ Ω·cm, B = 3278.21 K). This study developed a multi-scale control strategy encompassing composition design, sintering densification, and defect elimination. Utilizing this strategy, the material with a composition of x = 0.18 exhibited optimized electrical properties (resistivity ρ = 10⁴ ~ 10⁶ Ω cm, B-value > 3000 K) and stability (aging rate < 1%). This work provides engineering-guided process guidelines for developing high-precision thermistor components.