Thermal stability of interhalogen compounds
More electronegativity difference generally gives you stronger bonds,  therefore higher thermal stability (i.e. you need to put in more energy to break them). Also, there are 2 lone pairs on the central atom and 3 on each F. Thus, interhalogen compounds of this type with larger central atom would experience less electron pair repulsion. So, I believe that the correct order is $\ce{IF3&gt;BrF3&gt;ClF3}$ as you suggested.