Effect of annealing in O2 or N2 on the aging of Fe0.5Mn1.84Ni0.66O4 NTC-ceramics

Abstract

Fe 0.5 Mn 1.84 Ni 0.66 O 4 NTC ceramic thermistors were annealed in nitrogen or oxygen atmosphere at 600°C. The change of the electrical properties of the thermistors with time was reduced sharply by annealing in N 2 , whereas it was enhanced upon annealing in O 2 . N 2 -annealed samples exhibited a less degree of redistribution of cations in the lattice as compared with O 2 -annealed samples. The aging of the electrical properties is believed to result from the cation redistribution which in turn is favoured by the presence of cation vacancies. And the improved aging behaviour of the N 2 -annealed thermistor is explained by the reduction of the concentration of the cation vacancy upon annealing under lower oxygen partial pressure and the suppression of cation redistribution.

Negative Temperature Coefficient Resistance (NTCR) Ceramic Thermistors: An Industrial Perspective

“…98 Both vacancies will occupy their thermodynamically favorable site, which will result in electrical drifts. 101 Their observations were in agreement with Groen's model. This increase B-site vacancies inside the grains results in an increase of resistivity, because the conduction in these materials occurs by electron or hole hopping over the B-sites.…”

“…50,85,[93][94][95][96][97][98][99][100][101][102][103] Nevertheless, most investigators are still divided concerning the exact origin of the aging of the electrical properties of spinels; however, theories based on redistribution of charge over time are often evoked. 50,85,[93][94][95][96][97][98][99][100][101][102][103] Nevertheless, most investigators are still divided concerning the exact origin of the aging of the electrical properties of spinels; however, theories based on redistribution of charge over time are often evoked.…”

“…From the 1990s onwards there has been a considerable amount of research aimed at understanding aging in NTCR ce-ramics, as attested by a considerable number of publications in the literature. 50,85,[93][94][95][96][97][98][99][100][101][102][103] Nevertheless, most investigators are still divided concerning the exact origin of the aging of the electrical properties of spinels; however, theories based on redistribution of charge over time are often evoked. This may occur by diffusion of cationic vacancies or changes in the degree of inversion.…”

Nickel on alumina catalysts for the production of hydrogen rich mixtures via the biogas dry reforming reaction: Influence of the synthesis method

“…It was suggested that the observed reduction peaks, as well as their position could be related to the different Ni 2þ coordination in the spinel framework. Furthermore, they concluded that as the contribution of the b-peak in the total Ni species present in the spinel structure of NiAl 2 O 4 -CD was lower (27%) than that of NiAl 2 O 4 -CP (51%), the Ni 2þ ions occupying octahedral sites were more prone to reduction than the tetrahedral ones, as in the case of our 8NiAl-edf catalyst Thus, such results strongly support that the reforming efficiency is highly dependent on the type of interaction of the Ni active phase with the carrier [38,81,82].…”

An efficient way to improve the electrical stability of Ni0.6Si0.2Al0.6Mn1.6O4 NTC thermistor

“…It is generally accepted that the exchange of cations between sublattice tetrahedral (A-sites) and octahedral (B-sites) result in the aging of Fe-containing NTC thermistors [4,[7][8][9][10][11][12][13]. Besides, some studies showed that the aging also involves migration of cation vacancies from the grain boundaries to the interior [14].…”