Electronic structure modulation and electrical property tuning of LaMnO3-based NTC ceramics via Cu doping

A novel perovskite-type low-temperature thermistor ceramic, LaMn 1-x Cu x O 3 (0 ≤ x ≤ 0.5), was synthesized utilizing the sol-gel technique. X-ray diffraction (XRD) analysis verified the successful formation of a single-phase perovskite structure throughout the entire compositional range. Scanning electron microscopy (SEM) observations indicated that an increase in Cu 2+ doping concentration resulted in grain growth and a morphological evolution from square-shaped to polygonal grains. For all samples, the resistivities (ρ 65K ), activation energies for electrical conduction (E a ) and thermal constants (B 65/150 ) were in the ranges of 0.380 to 6.247 MΩ cm, 0.066 to 0.128 eV and 835-1213 K. The electrical characterization of LaMn 1-x Cu x O 3 ceramics demonstrates conformity with the small polaron conduction model. Analysis through impedance spectroscopy reveals that the electrical resistivity of the material is primarily controlled by grain boundary resistance. This study emphasizes the enhancement of electrical properties and the modulation of the band structure achieved through Cu 2+ ion doping, thereby offering a viable approach for the advancement of high-performance LaMnO 3 -based negative temperature coefficient thermistors operating at low temperatures.