AC charging/discharging of de-alloyed Si–Al–V alloy ribbons

• Al and V of Si–Al–V alloys are de-alloyed by acid leaching.
• De-alloyed alloys have large number of nanometer-sized canyons on their surface.
• De-alloyed alloys show prompt charging/discharging characteristics.
• The alloy consists of electric distributed constant capacitors.

In anticipation of prompt ac charging/discharging characteristics, the capacitance of de-alloyed Si1−x(Al0.5,V0.5)x (x = 0.15, 0.2, 0.3, and 0.4) alloy ribbons with resistivities of 0.01–4300 Ωcm was measured as a function of frequency between 1 mHz and 1 MHz, using exponential transient analysis for electric charging/discharging. The capacitance of de-alloyed Si–7.5 at.%.Al–7.5 at.%. V obtained by prompt (100 ms–25 ns) charging/discharging decreased logarithmically from 105 μF to 18 pF as frequency increased from 1 mHz to 10 kHz, and then saturated between 10 kHz and 1 MHz. From the observed electrode distance dependence on capacitance, we deduced that the alloy consisted of a distributed constant equivalent circuit (series with 1.2% parallel), analogous to electric double layer capacitors.