I did TGA of a LiFePO4 (LFP) sample and obtained a 3% of weight increase (heating rate of 10ºC/min till 700ºC and cooling down at 10ºC/min). I repeated the analysis several times, both in argon and in N2 atmosphere and using different equipment. I have also done the analysis circulating N2 at room temperature for one hour to remove possible O2 adsorbed on the LFP. I know my LFP is oxidizing during the analysis, but I still don't understand how I can have an increase in weight. Any ideas?
Thanks!!
I have no experience with this particular material, but from our works with nanometals (e.g., nano-Ti) and some reactive polymeric systems we indeed observe the effects by resildual oxygen remained in typical STA apparatus even when one suppose to have an inert atmosphere. It surely depends on apparatus type, furnace volume, the way you shift to the inert gas (e.g., with vacuum pumping or just flushing). The best results we have were after >3 evacuation-filling cycles prior to measurement, but the resudual air is there. Some manufactures (Netzsch) have getters that can be attached to the sample carrier to further decrease the resdual air influence
Hope that helps,
NM
Maria Castellví Barnés, I recommend doing a correction measurement without your material, then you proceed with your material.
In case you are using Netzsch STA equipment you can turn TGBeflat support on.
I hope that works.
Thanks for your answers.
I did a blank with the empty crucible and it doesn't explain the weight increase. The only explanation I could think of is that, somehow, there is some residual oxygen as Nikita mentions. However, I find it strange that I still get the same results after flushing N2 during 1h.
Further input:
You need to perform blank rub and baseline correction (calibration of ASTM Std) in Al2O3 alumina crucibles. To observe any TG weight gain or loss at the beginning, try 1 hour holding your sample at 100°C to evaporate any moisture content, then perform Argon purging at 200ml/min for 10 minutes. Repeat 100°C heating period before ramping to 700°C at 10°C/min heating rate.
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