Preparation and characterization of spinel-type Mn-Ni-Co-O negative temperature coefficient ceramic thermistors

• Published in: Journal of materials science 1998, Vol.33 (6), p.1491-1496
• Main Authors: MARTIN DE VIDALES, J. L, GARCIA-CHAIN, P, ROJAS, R. M, VILA, E, GARCIA-MARTINEZ, O
• Format: Article
• Language: English
• Subjects: Applied sciences; Building materials. Ceramics. Glasses; Ceramic industries; Ceramic powders; Ceramics; Chemical industry and chemicals; Density; Dilatometry; Electrotechnical and electronic ceramics; Exact sciences and technology; Manganese; Materials science; Mathematical analysis; Nickel; Scanning electron microscopy; Sintering (powder metallurgy); Spinel; Technical ceramics; Thermistors; X ray powder diffraction
• ISSN: 0022-2461; 1573-4803
• DOI: 10.1023/A:1004351809932

Powders of ternary Mn–Ni–Co oxide negative temperature coefficient thermistors were synthesized by a low-temperature alternative route. The procedure allowed straightforward preparation without the addition of any binder, of highly densified Mn–Ni–Co–O semiconducting ceramics as cubic single-phase spinels, at relatively moderate temperature (≈1000 °C). A tentative cation distribution for the Mn1.5Ni0.6Co0.9O4 spinel oxide has been proposed, and its variation with temperature has also been considered. The dilatometric and X-ray powder diffraction studies carried out for Mn1.5Ni0.6Co0.9O4 showed that sintering takes place in a single stage between 900 and 1000 °C, and yields highly densified ceramic with an apparant density larger than 96% of the calculated X-ray density. Scanning electron microscopy showed different microstructures for the Mn1.5Ni0.6Co0.9O4 spinel oxide, depending on sintering conditions. The value of the sensitivity index, β=3068 K, indicates a good technological thermistor performance for this material. © 1998 Chapman & Hall