Instead of taking heating run take cooling run from higher temperature and spot the first exothermic peak during cooling.

Thanks for the answer, please see the attached image of the DSC plot. I think the system is so complicated. We expected to see the melting point around 390 0C.

Dear Zahed,

What is the heating/cooling rate? Have you tried to carry out the DSC measurement for pure constituents? Are you sure about the purity of your compounds? Is it homogeneous?

Regarding your question, you can easily determine the melting point/phase transition enthalpy, until you can find the proper baseline. It can be done in every DSC software (normally distributed by the equipment supplier, however, you can do it also manually). 

There are many questions/issues which must be considered. Feel free to contact me on mail: [email protected]

 Thank you Kamil, the first 2 heating/cooling cycles rate was 20 0C/min and the third was 10 0C/min. No the salt mixture is not pure. 

Kind regards,

Zahed. 

What crucibles are you using? You need to make sure you are not reacting with the crucible. 

Dear Martin,

Is your mean the pan used for DSC running or the crucible used for making the salt mixture eutectic?

Kind regards,

Zahed.

Dear Zahed,

Did your salts react with the crucible/pan for DSC?

Did you measure the mass before and after the DSC? Was the mass the same? Did you lose some F?

If you place your material in a furnace and perform the same heating and cooling profile then take your sample to an XRD, is your material the same as you started?

Cheers,

Martin

Dear martin,

Thanks for the answer, yes, we have recorded the weigh for the samples before and after DSC runs and we observed that the weigh of the salt mixture decreased. We are going to do an XRD after making the salt mixture in a furnace.

Best,

Zahed.

Hi All,

What is the reason for the more intense DSC Heat Flux at higher ramp rates?

Kind regards,

Zahed.

What crucibles are you using? You need to make sure you are not reacting with the crucible. 

Dear Martin,

I tested 3 DSC pans including graphite, Al, and gold. The higher  ramp rates give the intense peaks. Gold pan is inert.

Kind regards,

Zahed.

Please post all your DSC curves with TG. Plot Enthalpy on the y axis and temperature on the x axis. Post separately for heating and cooling. Lets have a look.

Fluoride materials are very hard to work with. I am sure you have pitted your measuring head as your samples have decomposed.

Dear Zahed,

 These curves look more like what you had stated in your second comment in this forum:

"We expected to see the melting point around 390 DEG C."

Your curves look much better than the original ones you posted.

Did you lose mass? If you did and 30 DEG/min was your first run, then it would make sense that there would be more area under the curve for this endothermic occurrence.

It seems that you have two occurrences happening around 400 and I guess that you really want to deconvolute these occurrences to see what is going on. Here are my suggestions for this:

                1. Run an STA whereas you could possibly attribute one to the mass loss of the disassociation of a certain phase of material.

                2. High-Temperature Temperature-Modulated Differential Scanning Calorimetry (TM-DSC) by Netzsch

                3. Run these in a heated E-SEM and physically see what goes on to your salts

Running Fluoride materials in most instruments can be a problem, so good luck.

Cheers,

Martin