Cold sintered semiconducting composites through integrating 2D MXene into the grain boundaries of Na₂Mo₂O₇ dielectric ceramic

With the rapid development of electronic industry, there is an increasing demand for electro-ceramics with enhanced performances. Two-dimensional materials typically exhibit unique physicochemical properties, making them promising candidates for ceramic-based composites. Herein, one-step cold sintering process is proposed to tailor the microstructures and performances of Na₂Mo₂O₇ ceramics through the incorporation of Ti₃C₂T_x (MXene) material. Using de-ionized water as a transient liquid phase, (1 − γ)Na₂Mo₂O₇-γTi₃C₂T_x (NMOM) composites are densified at 120 °C. The MXene nanosheets are uniformly distributed along the grain boundaries, forming continuous conductive networks, which significantly enhance the overall electrical conductivity and transform Na₂Mo₂O₇ from dielectric to semiconductor. The negative temperature coefficient (NTC) behavior and material constant of the composites are manipulated by tuning the MXene content. A high material constant of 7324 K and temperature coefficient of resistivity of −7.0% K⁻¹ are achieved, with the conduction mechanism dominated by small polaron hopping and an activation energy of 0.63 eV. These findings highlight the potential of NMOM composites for NTC thermistor applications and demonstrate cold sintering process as an effective route for the design of high-performance semiconducting ceramics with MXenes.