Evaluation of Ohmic Peak Characteristic of Metal/Clay Based Cermet

International Journal of Research and Scientific Innovation (IJRSI) | Volume VI, Issue IX, September 2019 | ISSN 2321–2705

Evaluation of Ohmic Peak Characteristic of Metal/Clay Based Cermet

F. O. Omoniyi

Department of Physics, University of Abuja, Abuja, Nigeria

Abstract: The Ohmic peak of copper/clay based cermet is evaluated to know the Ohmic boundary and response of the fabricated cermet resistors, using electrically conducting and chemically active copper powder with mass 5%, 15% and 25% using Archimedes’ principle. Considering annealing temperatures ranging from 200 ºC to 500 ºC. Some compositions exhibit inverse size feature earlier or later. The results showed that, the threshold resistivity for copper compositions gets closer to peak from 400 ºC while the 25% copper exhibited higher resistance peak than the lower compositions.

Keywords: Intercalate, Percolation, Annealing, Ohmic, Threshold.

INTRODUCTION

Today, ceramics are routinely implemented in the combustor part of the jet engines because the blade provides heat resistant chamber [1]. Cermet consist of a thorough mixture of a ceramic hard phase and a suitable metal binding phase [2] that enables Ohmic property (Ohm’s law R=ρL/A, R is resistance, ρ is resistivity, L is length and A is the cross sectional area). The resistance/resistivity of the metal-clay cermet resistors varied remarkably with conductive grain content, firing sequence (firing time, firing atmosphere and peak firing temperature) and the length of the resistor [3], [4], [5]. Exchange and redox reactions make the microstructure and electrical properties of the insulating layers very variable according to the firing condition [3], likewise re-firing which resulted in temperature shift from positive to negative of temperature coefficient of resistance (TCR) [6]. Cermet structured resistors, like thick film resistors (TFRs), exhibit a high stability and very low TCR [7]. The TCR of a thick film composite is determined by the separate temperature coefficient of its conducting constituents in their final form after annealing [8], [9]. Hence, the conduction in composite resistor is similar to that in cermet film resistors [10]. Annealing sequence is said to affect greatly the electrical properties of cermet/composites due to structural defects like impurity atoms, vacancies, interstitial and grain boundaries that are produced [7], [11].

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