I prepared some MgB2 strand sample in lab scale to characterize the powders. Strands prepared through In-situ route are showing better result but at the same time Ex-situ processed wires are not successful. Many paper explained about superconductivity in Ex-situ processed wire without heat-treatment. I tried with different heat-treatment temperature and different time duration.
Plz explain me some probable reasons of failure in getting superconductivity in Ex-situ processed MgB2
I dont have much idea on superconductivity but have you counted of getting oxidized of MgB2 to MgO at atmosphere? That is why it is showing the superconductivity in in-situ not ex-situ.
Dear Sujoy sir & Elman sir,
Thank you very much for your suggestions.
Is there any procedure to confirm the presence of MgO layer over th MgB2 powders.
How can I remove these layers. I read in some research papers about cleaning of powders in some chemicals. But they have not mentioned the name of the chemicals. can you guide me?
Dear sir (Elman Shahverdiev),
Thank you very much for your valuable information. is it possible that inter-grain boundaries could be play a role when MgB2 converted into MgO by ex-situ treatment.
Dear Subrat,
it seems you are not too precise with describing your attempts. If you wrote about the".. failure in getting superconductivity in Ex-situ processed MgB2." I suppose you were conducting electric transport measurements. Only in such a case ex-situ powder might be called non-superconducting. On the contrary I believe it will show superconductivity while making magnetic measurements. In such measurements both types of your wires will show superconducting behavior with similar critical temperatures and magnetic screening.
Making I-V charcateristics of the wire you probably use short pieces of the wire and you employed four-contacts method. Making such measurements you should be aware about the so called "tranfer length". It is the distance along the wire necessary for current to get from the surface contact to superconducting material inside. This distance is dependent on the many variables (material of the wire sheath and/or berrier, contacts between the superconducting grains, geometry of measurements etc.). Very often, if the voltage measuring contacts are closer to the current contacts then transfer langht, the effect of I-V measurements is striht line imiting Ohm's law (but with the lower slope then characteristic to sheath and/or barrier resistivity for that temparature). The solution to avoid the problems with the transfer langht is to use longer pieces of the wire and making voltage contacts closer. This in turn requires measurements with higher sensitivity and effects noise.
Dear Elman sir,
i have gone through the paper and i would like to try the same. In that paper they have mentioned to dip the MgB2 powders in the non-aqueous solution. Is there any specific instruments which can be used for handling during etching of these nano-sized powders?
Thank you sir
Respected Andrzej Janusz Zaleski sir,
I followed four probe measurement technique for Jc measurement. I followed the same procedure for in situ and ex-situ but i failed in the Ex-situ samples only.
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