I have prepared ZnO as well as Al-doped ZnO powder via co-precipitation method. When I press the powder to pellets for electrical measurement either through cold press followed by sintering or Hot press, both the cases pellets are showing too much resistance (order of 10 power 5-6).Can someone suggest how can I reduce the resistance ?
Hello Krishna,
I would like to know that whether you tried applying the silver paste (comprises of Ag particles dissolved in Amyl acetate)?
This is used to make the top and bottom surface conducting before doing any electrical measurements.
The answer to your question is as follows:
Usually, semiconducting materials that behaves like actually behaves like Semi-Conductors, are having a band gap of
Thank you Anshuman. I didn't apply silver paste. I want to measure the electrical conductivity as well as Seebeck coefficient. For this measurement i need the sample which should have minimum resistance of the order of 100 ohm. And also I am not interested in film. I have another doubt that If I apply silver paste whether it will be harmful for the instrument or not(Since I want to measure the el. conductivity and Seebeck coefficient from room to high temperature.)
As far as impedance spectroscopy is concerned, silver paste can withstand a temperature upto few approx. 300-400 deg C (only in case, if your pellet is properly sintered). Beyond certain temperature, silver particles penetrate in pellet thus deviating our real output as Ag is itself a very good conductor.
Similar in Seebeck effect , you have to optimize the conditions upto which your sample remain good.
You have to apply a very thin layer of silver paste to the pellets in order to measure the electrical parameters like conductivity, loss tangent, capacitance, etc. Applying silver paste does not change any parameter in the ZnO pellet to about 500 deg C with proper sintering (to atleast 600 deg C) and the 100 ohm resistance you had talked does not come up here as Ag is a good conductor. Please see my published papers in ZnO. I had doped with Al, Ru and Cu. You will have a good idea of the queries.
Best of luck.
Thanks Arindam and Anshuman for your answers.My pellets are in a good sintered condition. I have sintered those at 1300 C.Thanks again Arindam. I will go through your papers for a better idea.
Did you do sintering in vacuum furnace or not. Oxygen vacancy makes great difference. I would suggest you to sinter in partial oxygen or air.
Zinc oxide bulk material is not conductor, but in case of thin films, the excess of oxygen act as dopant and increase the conductivity
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