The specific grain-boundary electrical resistivity of Ni

Abstract

The purpose of the present study was to provide a reliable value for the specific grain-boundary resistivity ρ SGBR of Ni metal. New results are presented on the room-temperature electrical resistivity of nanocrystalline (nc) Ni metal samples produced by electrodeposition with various grain sizes. These resistivity data were compared with previous reports on nc-Ni and all results were analysed according to the procedure of Andrews [Phys. Lett. 19, 558 (1965)] who found that the resistivity increment due to grain boundaries is proportional to the grain-boundary surface area per unit volume which is, on the other hand, inversely proportional to the grain size. It is pointed out that the grain size directly accessible by transmission electron microscopy imaging is the relevant parameter for the evaluation of ρ SGBR whereas the crystallite size deduced from X-ray diffraction line broadening leads to an underestimation of ρ SGBR because coherency-breaking intragrain defects not contributing significantly to the resistivity also cause a line broadening. From the evaluation of the nc-Ni resistivity data at room temperature, we find that 4.45•10 −16 Ω•m 2 < ρ SGBR (Ni) < 6.2•10 −16 Ω•m 2 and our upper bound agrees exactly with the most recent calculated value in the literature.

Room-temperature magnetoresistance of nanocrystalline Ni metal with various grain sizes

“…This was, indeed, often observed for nc-Ni as summarized in Ref. [6] in which we have analyzed the grain-size dependence of the zero-field resistivity (ρ o ) of the current electrodeposited nc-Ni samples together with all previously reported relevant data to extract the specific grain-boundary resistivity of Ni metal.…”

“…Although no structural study was carried out for the two other above mentioned Ni foil samples (#Ni(99.99+ %) and #GF-Ni(50 μm)), they should exhibit fairly similar structural features as sample #B5, i.e., they can also be considered as representing bulk Ni. This is further supported by the fact that the room-temperature zero-field resistivity of all these samples was in good agreement with that of bulk Ni [6]. (2) Electrodeposition (ED) was used to prepare about 20 μm thick nc-Ni foils with grain sizes ranging from 30 to 100 nm.…”

“…The results of electrical transport measurements to be presented here were obtained on the same metallurgically processed and electrodeposited pure Ni metal foil samples for which we have recently reported room-temperature zero-field resistivity data [6]. Therefore, only a brief description and characterization of these samples will be given here.…”

“…The structural characterization of sample #B5 revealed [6] that this Ni foil sample can be considered as representing the bulk state of Ni (it can also be termed as microcrystalline (μc) Ni since it exhibits grain sizes in the micrometer range). Although no structural study was carried out for the two other above mentioned Ni foil samples (#Ni(99.99+ %) and #GF-Ni(50 μm)), they should exhibit fairly similar structural features as sample #B5, i.e., they can also be considered as representing bulk Ni.…”

“…[14] and [15] and their zerofield resistivity data were reported in Ref. [6]. Two other electrodeposited Ni samples (sample #B2 and #Ni(TKE)) prepared earlier under different conditions were also investigated and structurally characterized in Ref.…”