Preparation and characterization of NTC thermistors: Nickel manganites doped with lithium
Abstract
Oxides of the form Ni(x)Mn(3-x)O4 present properties that make them useful as NTC thermistors. Nickel manganites doped with lithium were synthesized by two methods: insertion with n-BuLi and reaction of nickel-manganese formates with lithium formate. XPS and XRD studies showed that both procedures led to oxides with spinel structure, although with different cation distributions. Dilatometry established that a cationic reordering took place on manganites doped by insertion with n-BuLi during sintering. SEM mapping studies showed that a segregation on grain boundaries took place, leading to an increase in Mn content and a decrease in nickel on the particle surface. Finally, electrical studies showed the nickel manganites doped with lithium, Ni(x)Mn(3-x-y)Li(y)O4, had similar resistivities and sensitivity indexes to nickel manganites, Ni(x)Mn(3-x)O4, but higher electrical stability.
- Publication:
-
Journal of American Ceramic Society
- Pub Date:
- April 1995
- Bibcode:
- 1995JACS...78..915M
- Keywords:
-
- Additives;
- Lithium;
- Manganese Oxides;
- Microstructure;
- Nickel Oxides;
- Synthesis (Chemistry);
- Thermistors;
- Composition (Property);
- Electrical Resistivity;
- Grain Boundaries;
- Photoelectron Spectroscopy;
- X Ray Diffraction;
- X Ray Spectroscopy;
- Electronics and Electrical Engineering