Mn/La co-doped WO₃ (Mn_xLa_0.03WO_3+δ, x ≤ 0.1) ceramics for NTC thermistors

The low sintering temperature (LST) is a great significance for the fabrication of sensors and electronic components. To exploit a system of LST negative temperature coefficient (NTC) thermistors, Mn/La co-doped WO₃ ceramics (Mn_xLa_0.03WO_3+δ, x ≤ 0.1, denoted as xMLW) were prepared in this work by a traditional solid-state reaction technology. The phase component, microstructure, and electrical property of the prepared xMLW ceramics were investigated. The xMLW ceramics have the main phase with lattice structure as that of monoclinic WO₃ with a space group of P21/n, and show typical NTC characteristics. By varying the concentration of Mn cations, the xMLW ceramics have adjustable room temperature resistivity (ρ₂₅) ranging from 770 Ω·cm to 7.017 kΩ·cm and high thermal-sensitivity constants (B value) ranging from 2695 to 4219 K. The electrical conduction and NTC feature of the ceramics are discussed by analyzing impedance spectrum and lattice defect.