Fast response and high stability Mn‐Co‐Ni‐Al‐O NTC microbeads thermistors

Herein, Al-doped Mn1.95Co0.21Ni0.84O4 (MCN)-microbead structures were successfully prepared using in situ ink-jet printing technology. The effects of the Al2O3 doping on the electrical properties of the MCN ceramic microbeads were discussed. The R-25, B-25/50, and E-a values of NTC ceramics thermistors were found to range from 14.14 x 10(3)-63.21 x 10(3) omega, 3635-3773 K, and 0.3133-0.3252 eV, respectively. Notably, the ageing coefficient (Delta R/R) of the (Mn-Co-Ni-Al-O) MCNA ceramics was found to be <1.1%, compared to a value exceeding 4.2% for the undoped MCN microbeads. The thermal time constant of the doped microbeads was small, with a value of 33 ms, compared to 8 s for the MCN ceramic chip. In particular, the grain boundaries were determined to play an important role in the overall electric behaviour of the ceramics described here.