Impedance analysis of MnCoCuO NTC ceramic

Journal Article · Tue Jul 12 04:00:00 EDT 2005 · Materials Research Bulletin

DOI:https://doi.org/10.1016/j.materresbull.2005.04.001· OSTI ID:20889793

Song, S G ^[1]; Ling, Z ^[2]; Placido, F ^[1]

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1. Thin Film Centre, University of Paisley, PA1 2BE Paisley (United Kingdom)
2. Microscale Sensor Group, University of Paisley, PA1 2BE Paisley (United Kingdom)

Impedance spectroscopy is often used to analyse the electrical properties of ceramic materials having high-resistive grain boundaries, such as ZnO and SrTiO{sub 3}. Fewer attempts have been made at using this technique for the analysis of inhomogeneous electronic ceramics consisting of grains with differing composition, such as those occurring in negative temperature coefficient (NTC) thermistors. In this study, we have attempted to adopt ac impedance spectroscopy together with other techniques to analyse an NTC thermistor ceramic material. An Mn, Co and Cu multielements transition metal oxide (MnCoCuO) ceramic was prepared by using homogeneous precipitation employing oxalic acid. This material displayed a typical NTC effect, showing an electrical resistance decrease with temperature when dc electrical measurement was performed. The ac impedance spectroscopy analysis showed that there were two peaks in impedance and conductance versus frequency plot. By using an alternative representation of impedance spectra Z'/f versus Z', three distinct relaxation frequency ranges were identified. They are believed to originate, respectively, from the electrode, phase 1 (rich-Cu phase) and phase 2 (poor-Cu phase) grains existing in this ceramic. SEM observation and EDX analysis clearly showed existence of two distinct phase grains. The resistance values were derived from phases 1 and 2 grains based on ac impedance data. The sum of the resistance values was in good agreement with that from dc measurement in the temperature range of 30-95 deg. C. The material constant, B, for the two phases was also calculated, giving 3100 and 3600 K for phases 1 and 2, respectively.

• OSTI ID: 20889793
• Journal Information: Materials Research Bulletin, Journal Name: Materials Research Bulletin Journal Issue: 7 Vol. 40; ISSN MRBUAC; ISSN 0025-5408
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
CERAMICS
COBALT
COPPER OXIDES
ELECTRIC CONDUCTIVITY
FREQUENCY RANGE
GRAIN BOUNDARIES
IMPEDANCE
MANGANESE
OXALIC ACID
PRECIPITATION
SCANNING ELECTRON MICROSCOPY
SPECTROSCOPY
STRONTIUM TITANATES
TEMPERATURE COEFFICIENT
TEMPERATURE RANGE
THERMISTORS
ZINC OXIDES