1. An ionic liquid (IL) is by definition a salt-like compound which does not solidify (crystallise) at ambient conditions.

2. To this end the anion and cation were chosen to have only poor ionic potential towards each other to keep the lattice energy low, right?

The answer is: if you use conventional ionic liquids you have to cool them far below room temperature, to crystallise them (see point 1).

Of course, due to point 2, ILs crystallise intrinsically quite badly. To change this you can think about playing with the chemical components. E.g. long chain alkanes attached to the anion or cation might yield in soap-like crystallisation. Aromatic groups on the anion or cation (or on both) might induce crystallisation by pi-stacking.

Maybe you tell us more about the chemistry of your ILs then we can think about practical solutions.

Best

@Axel

Sir, I am using Imidazolium based cation instead of phosphonium to get IL's to crystallize moreover, I also have 3 napthalene rings coordinating to metal, in the anion as well along with having Oxygen in the anion structure, so I believe there is potential for Hydrogen bonding and pi-pi stacking in my Magnetic Ionic Liquids

But I haven't been successful yet to find optimum conditions for Crystallization, if you can guide me in this regard, that would be grrat