Why on TGA I get a weight gain about 6% analyzing Zn4Sb3? All knowed causes (buoyancy, impurities, calibrations of the instruments) are excluded. From which procent this increase can be seriously taken into account?
I don't know what kind of atmosphere you have, sometimes air or nitrogen can react with sample, this is the reason argon is preferred.
If the atmosphere is synthetic or natural air, formation of surface oxides and/or nitrides is the most likely reason for the observed weight increase. Depends on the upper temperature limit you have been using in your measurement.
The TGA measurements in the intermetallic compounds don’t actually have much sense as the only weight change can be actually associated with interaction of the atmosphere and your sample. DSC/DTA measurements can eventually reveal structural phase transitions in your sample if they are in the range of your temperature measurement boundaries.
Beside the experimental errors and other phenomena that you cited, the interaction between the gas used (N2, air) and the sample can cause such a result. If it is the case, an inert gase like argon can be used .
I used Ni2 and the experiment was taken from room temperature to 1000C. It may be Ni2 the cause of the weight gain, although in literature I found similar experiments on Zn4Sb3 taken in Ni2.
Thank you very much for your answers.
Oxidation or nitride formation depending on ambient. try using argon or helium.
It is could be gas solid reaction which produce a solid phase! you may find a probable reactions in the literature.
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