Cobalt-free NTC ceramic and method for producing a cobalt-free NTC ceramic

A method for producing a cobalt-free NTC ceramic, the composition of which is derived from a cobalt-containing NTC ceramic having the general formula NiaCubCocMndO4 with 0.09<a<0.6, 0.02<b<0.65, 0.12<c<0.58 and 1.6<d<2.1, Co being replaced by Zn, comprising the method steps:

• A) formal decomposition of NiaCubCocMndO4 into spinel components, which respectively contain at least one oxide of Ni, Cu, Co or Mn,
• B) formal replacement at least of the cobalt-containing spinel components by cobalt-free spinel components,
• C) formal composition of the at least partially replaced spinel components to form an intermediate stage having the composition NiαCuβZnγMnδO4 with 0.09<α<0.6, 0.02<β<0.65, 0.12<γ<0.58 and 1.6<δ<2.1,
• D) adaptation of α, β, γ and δ in order to obtain a composition Nia′Cub′Znc′Mnd′O4 with 0.09<a′<0.6, 0.02<b′<0.65, 0.12<c′<0.58 and 1.6<d′<2.1, wherein the adaptation is carried out while assimilating the electrical properties of the cobalt-free NTC ceramic to the electrical properties of the cobalt-containing NTC ceramic,
• E) production of a ceramic having the composition Nia′Cub′Znc′Mnd′O4 from starting substances, wherein the starting substances are mixed in the stoichiometric ratio of the metal cations as determined by method steps A) to D) and wherein a′, b′, c′ and d′ are as defined in step D above.