Study on ion migration characteristics and aging stability of MgTiO₃ and LaTiO₃ composites ceramic for high temperature negative temperature coefficient ceramics

It was found for the first time that high temperature negative temperature coefficient (NTC) composites ceramic of La_1−xMg_xTiO₃ (x = 0.1, 0.3, 0.5, 0.7, 0.9) have been prepared by the solid-state reaction method sintered at 1400 °C. The effects of MgTiO₃ and LaTiO₃ composites on the structure, electrical properties and stability of the sintered ceramic samples were characterized by thermogravimetry–differential scanning calorimetry (TG–DSC), X-ray diffraction (XRD), scanning electron microscope (SEM), energy-dispersive spectroscopy (EDS), Mapping, X-ray photoelectron spectroscopy analysis. XRD patterns analysis has revealed that for La_1−xMg_xTiO₃ (x = 0.1, 0.3, 0.5, 0.7, 0.9) the major phases presents in the calcined bodies are double perovskites the LaTiO₃ phase and the MgTiO₃ phase. The SEM images have exhibited that as the mole fraction of Mg²⁺ from 0.1 to 0.9, the grain size of the MgTiO₃ ceramics increases from ca. 1.77 to 5.99 μm and LaTiO₃ ceramics decreases from ca. 2.83 to 1.53 μm. X-ray photoelectron spectroscopy prove the Ti³⁺ and Ti⁴⁺ ions on lattice sites, which result in hopping conduction. The presence of the Ti³⁺ and Ti⁴⁺ ions is one of the significant factors that affect the electrical conductivity of La_1−xMg_xTiO₃ composites ceramic. The ρ₄₀₀ and B_400/1200 values are in the range of 14,693.137–65,659.809 Ω·cm and 7785.270–24,948.100 K, respectively. The La_1−xMg_xTiO₃ materials could be used as potential candidates for high temperature range from 400 to 1200 °C thermistors applications. The resistance variation (ΔR/R₀) was < 2% and the minimum value (0.1%) was obtained for aging at 1100 °C at 800 h. The aim of this work was exploring new composite ceramics materials, which could be used as higher temperature zones.