English

Achouri A,Mohammedi L,Boukraa A

doi:10.5897/ijps2016.4461

Abstract

We report on the simultaneous measurement of resistivity and Seebeck coefficients in samples of Pd81Ge19 ribbons prepared by the melt spinning technique method and having a typical dimension of 40.0 mm × 1.75 mm × 0.028 mm. The investigation was performed using a new completely automated device in a large temperature range (from room to 700°C). Structural changes, crystallization times and heat treatments on several samples of the same composition were followed as a function of temperature. Seebeck coefficients, reported for the first time in these samples, varied roughly between -2 and -21 µV/K in the temperature range of 25 to 700°C, while the electrical resistivity varied roughly between 35 and 120 µΩ.cm in agreement with the literature. Complementary differential scanning calorimetry (DSC) and scanning electron microscopy (SEM) experiments were also carried out and confirm the phase transitions observed by the above mentioned techniques. Key words: Seebeck coefficient, melt spinning technique, crystallization temperature, electrical resistivity, phase transitions.

Highlights

Crystallization kinetics of metallic glasses have been studied for many years (Calvo-Dahlborg et al, 1997) and they continue to be an attractive field because of their interesting properties for industrial applications
Continuous resistivity and Seebeck coefficient measurement curves show a drastic and important change before the melting temperature is reached characteristic of a behaviour which occurs in amorphous phases
The amorphous material crystallizes and a marked change is observed in resistivity and Seebeck coefficient curves corresponding to crystallization temperatures

Summary

Introduction

Crystallization kinetics of metallic glasses have been studied for many years (Calvo-Dahlborg et al, 1997) and they continue to be an attractive field because of their interesting properties for industrial applications. The physical properties depend on their chemical composition and production process (Calvo-Dahlborg et al, 2011) Among their cited properties are electrical resistivity and Seebeck coefficient, which are directly related to the atomic structure and the coupling between them can often be used to characterize the electrical conduction mechanisms in solids (Dordor et al, 1980; Mott and Davis, 1971). Budhani et al (1983) studied the variation of the resistivity as a function of temperature for Pd80Ge20 and Pd77.5Ge22.5 continuously heated at 10°C/min through the temperature range 300 to 710 K They observed that the crystallization process starts around 600 and 550 K respectively in a direct transformation.

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