What is the procedure for make pellets for ferroelectric studies and silver paste coating on pellets surfaces?
Make the pellets using conventional method. I hope you have a pellet die. You can screen print/doctor blade film/vacuum evaporation silver on the surface. Best is screen printing. Most simple you can have film using doctor blade technique.
Dear Dr. Subramaniyan:
Electrical Measurements in Electroceramics/Ferroelectrics
Sample Preparation:
Superficies to receive electrode: perfectly parallel and high polishing degree, commonly reported as mirror like degree, from adjust of sample angle it is possible observe the eyes yourself.
Electrode preparation:
Ag Electrode: Ag 98% pure to 99.9% pure.
Electrode position: geometric center of sample, at simple configuration. Lines of electric field belong to the electrode border interact with sample.
Electrode aligning: both electrodes should be perfectly aligned.
Deposition: can be direct painting on the position. Some training is necessary despite of necessity of use a mask to protect almost sample surface; only area associated to electrode should be free.
Electrode fixation, first step: typically the Ag is disperse in a volatile solvent, then after painting gradual solvent elimination should be provided, at room temperature 24 hours can be sufficient.
Electrode fixation, second step: typically the Ag deposit is cured via thermal treatment. Under a slow hearting rate, in air atmosphere, temperature should be increased up to 200 oC – 250 0C, soaking time 2 – 4 h. Here, know-how is important since some parameters depending on the Ag particle size and its concentration. It is important, electrode characteristic via Scanning Electron Microscopy verifying, at least one time.
Electrodes in action: unfortunately, despite of low cost, Ag exhibits some temperature limitation of application. This event is not correlated with the fusion temperature 961 – 962 oC. In fact, the existence of a limit of application is assigned to other phenomena that are the good chemical interaction with inorganic materials and oxidation. In this sense, temperature of measurement can be limited to 350 oC to 400 oC.
Best regards
Marcos Nobre
In addition to the good answers above, the following steps should help:
1) Calcine the necessary mixture of powders and subject it to milling to ensure physical homogeneity (both pre and post calcination).
2) Incorporate an organic binder and use cold iso-static press to make 'green' pellets.
3) Sinter the green pellets while burying them in a powder of the same composition to prevent unwanted morphing/sticking/bending.
4) Use silver paint on polished surface and leave for 10-30 minutes. Alternately you could also fire the electrodes by placing the samples at 400oC in air.
5) Check for electrical conductivity.
I hope it helps.
Regards
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