MICROSTRUCTURE AND ELECTRICAL-TRANSPORT PROPERTIES OF PULSE-PLATED NANOCRYSTALLINE NICKEL ELECTRODEPOSITS

The microstructure and the electrical transport properties (the electr ical resistivity, its temperature coefficient and the thermoelectric p ower) were investigated for pulse-plated nanocrystalline nickel electr odeposits. Transmission and scanning electron microscopy were used to study the microstructure (grain size and lattice defects) and the surf ace morphology respectively. The samples were prepared from the same b ath as used previously for d.c. plating and the deposition current den sity was constant, in most cases i(dep) = 20 A dm(-2). In a given seri es, the pulse length t(on) was kept constant at 0.001, 0.01, 0.1, 1 or 10 s and the separation between pulses t(off) was varied from 0.001 s to 10 s. Systematic variations of the electrical transport parameters with t(on) and t(off) were observed, which we attempt to explain in t erms of the periodic variation due to pulse-plating of the local Ni2concentration at the cathode-electrolyte interface.