I prepared a ceramic material which is an high restive material, but after electroding its resistance is in the mega ohm. what would be the reason for it? it is because it is highly porous? or any other reason maybe?
Thanks for yours valuable suggestion....
Porous samples may absorb moisture and may increase conductivity drastically. Anneal your sample for two hour at 300 degree centigrade as ceramic sample may retain water molecules up to 250 degree centigrade.Even if the resistance does not come back go to x ray diffraction to find out other phases developed during electroding.
This may be due to the increase in conductivity, you must look through the setup and the type of your experiment. Some factors might change ( decrease the resistivity or resistance) this will help you in reasoning.
"but after electroding" - how you applied to the electrodes - conductive paste or sputtering or other method?
dear Pawel sir,, i have tried gold sputtering as well as silver paste by brush,,,but in both reason resistance falls in KILO or Mega ohm?
We do not know how thick are your samples and how they are porous - it can be opened and closed porosity. If the sample can be broken, and if the electrode penetrates through the pores then is quite easy clearly visible under an optical microscope.
Suman, Check density of your samples. That will give you idea about porosity.
You can also check porosity by dropping one drop of water directly on the pellet, if it is absorbed means sample is highly porous. Then you can conclude electroding may penetrate through the sample.
Second point is about your question. How you sure that your ceramic material has high resistance before electroding. How you checked its resistance before electroding. in that case you should follow your processing steps.
Dear Parveen SIR, according to literature survey its resistance in 10^8 orde but sir after electroding i found in kilo ohm,,,,,and sir i checked its denisty is 92 or 93 %.
Dear Suman, Did you check porosity? You should also match sintering conditions which you used and reported in a literature.
You can do impedance analyzes of your sample. That may give you to find out reason of the conduction process in your sample.
You also check whether is any volatile component in your sample composition, which may lead to vacancies.
Oxygen vacancies may also responsible for conduction. To reduce them, there is a number of ways like slow rate of cooling after sintering.
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