I feel that one of the main disadvantage of using powder sample for impedance analysis is that, there is a chance of migration of electrode through the sample and the highly conducting electrode will adversely effect your measurement data. Why cant you use sintered sample?

It is very unusual to measure the impedance of powders, because for almost all applications where the impedance is important you need bulk materials. If you still want to do it, I suggest to use a small cell designed for liquid electrochemical measurements. Instead of filling it with liquid, you fill it with the powder. The powder should be very fine-grained (i.e. small grain size) and should be compacted into the cell as much as possible. Impedance spectroscopy allows you to separate the bulk, grain boundary and electrode contributions in solid state samples. In powder measurements I would only regard the bulk response as being representative though. From well-sintered pellets you get the full information.

Firstly, I have furnace, where I can sinter in air only, but my powders can't be heated in air (N2 or Ar are needed). Offcourse I don't have a cell, designed for liquid electrochemical measurements too. But it would be interesting to see the conductivity of my powders. On the other hand, people really used to measure impedance of pressed powders, and it is interesting to know how they were doing this and maybe to tray in same case.

In this case I suggest you to search for a collaboration with a research group that has a furnace that can be used under different gas atmospheres. Maybe in a different department in your university? I do not recommend to measure pressed powders. The density is not going to be good and the air in between your particles will affect your measurments. The mechanical stability of your samples may be poor as well, which will lead to difficulties with the deposition of stable electrodes.

I used to measure impedance spectroscopy in pressed powder samples in a pressure cell, lined with ceramic and pressed with WIDIA pistons, I connected the pistons with point-welded copper platelets to the coaxial cables

Published in:

Rev. Sci. Instrum. 68, 193 (1997); http://dx.doi.org/10.1063/1.1147808 (4 pages)

Piston–cylinder apparatus for high-pressure impedance spectroscopy

R. Hinrichs1 and J. A. H. da Jornada2

Hi Vilma,

You can also measure the impedance by making the pellet of your sample and then connecting it with gold paste to gold electrodes.

Hi Vilma,

Impedance measurements required high density ceramics, typically more than 95% of the theoretical density to avoid surface resistivity contribution. We stated that resistivity measurements in alumina powders are governed by surface resistivity rather than volume resisitivity as expected. See atttached publication.

There is only one more reliable way to measure the electrical (close to DC bulk) conductivity of the powder. It is necessary to place your powders into a strong low frequency alternating magnetic field. Thus the eddy currents are excited in the crystallites. The mechanical force, the frequency of oscillating circuit or someone other may be measured. The method is very insensitive. Thus:

1. The powder must be high conductive;

2. Require large quantity of the powder;

3. Not suitable for ferromagnetics.

Impedance can be measure by impedance anayler Or IV probe method first maut pallets of powder than use silver paste for contact (electrod) .