Enhanced aging and thermal shock performance of Mn1.95-xCo0.21Ni0.84SrxO4 NTC ceramics

Abstract

Herein, the Mn1.95-xCo0.21Ni0.84SrxO4 (MCNS) (0 ≤ x ≤ 0.15) based negative temperature coefficient (NTC) materials are prepared by co-precipitation method. The replacement of Mn by Sr plays a critical role in controlling the lattice parameter, relative density, microstructure and electrical properties. The lattice parameter and relative density increase with the increase of Sr content. A small amount of Sr restrains the grain growth and increases the bulk density. Moreover, the ρ25, B25/50, Ea and α values of MCNS ceramics are influenced by the Sr content and ranged from 1535.0-2053.6 Ω·cm, 3654-3709 K, 0.3149-0.3197 eV and -4.111--4.173%, respectively. The XPS results explain the transformation of MCNS ceramics from n- to p-type semiconductors. The conduction could arise from the hopping polaron between Mn3+/Mn4+ and Co2+/Co3+ in the octahedral sites. The impedance data analysis also discussed the conduction mechanism of the MCNS ceramic, while grain resistance dominates the whole resistance of the samples. Furthermore, the aging coefficient (△R/R) of MCNS ceramics is found to be < 0.2%, which indicates the stable distribution of cations in the spinel. Finally, the MCNS ceramics demonstrate excellent thermal durability with <1.3% of resistance shift after 100 thermal shock cycles.

Extremely enhanced thermal stability of Y2/3Cu3Ti4O12 ceramics by a Pechini method

“…However, a small number of pores on the grain boundaries can be observed in the enlarged cross‐section micrographs of the YCTO‐S ceramics, as shown in Figure 5C. This is because the generation rate of grains is higher than the movement rate of grain boundaries 46,47 . In addition, the inhomogeneous grain size leads to a larger space between the grains, resulting in the formation of pores.…”

“…This is because the generation rate of grains is higher than the movement rate of grain boundaries. 46,47 In addition, the inhomogeneous grain size leads to a larger space between the grains, resulting in the formation of pores. The relative densities of YCTO-S and YCTO-P ceramics were 91.5% and 97.1%, respectively.…”