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Preparation of Ultra‐Fine Nickel Manganite Powders and Ceramics by a Solid‐State Coordination Reaction
Author(s) -
Fang Daolai,
Wang Zhongbing,
Yang Pinghua,
Liu Wei,
Chen Chusheng,
Winnubst A. J. A.
Publication year - 2006
Publication title -
journal of the american ceramic society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.9
H-Index - 196
eISSN - 1551-2916
pISSN - 0002-7820
DOI - 10.1111/j.1551-2916.2005.00666.x
Subject(s) - oxalic acid , oxalate , calcination , materials science , ceramic , electrical resistivity and conductivity , nickel , sintering , temperature coefficient , manganese , activation energy , manganite , inorganic chemistry , metallurgy , analytical chemistry (journal) , chemistry , catalysis , composite material , organic chemistry , engineering , physics , quantum mechanics , ferromagnetism , electrical engineering
A solid‐state coordination reaction was adopted to prepare negative temperature coefficient ceramics. A mixed oxalate NiMn 2 (C 2 O 4 ) 3 ·6H 2 O, a coordination compound, was synthesized by milling a mixture of nickel acetate, manganese acetate, and oxalic acid for 5 h at room temperature. An ultrafine NiMn 2 O 4 powder was obtained by calcining the mixed oxalate in air at 850°C for 2 h. Ceramics with a relative density of more than 97% were achieved by sintering powder compacts at a temperature as low as 1050°C for 5 h. The specific electrical resistivity ρ 25°C and the thermal constant B 25°/85°C were 2174 Ω·cm and 3884 K, respectively. The drift of the resistivity after aging at 150°C for 1000 h was 3.0%.