Why not?  Use 45 deg. geometry. you can also use filters to suppress excitation wavelength

yes you can use PL for power samples u need to make the pellet or just use powder sample holder.

I think you got the answer already given but be careful using pellet as it might not reflect the emitted light properly if you are using reflection mode. Better to have an accessory for thin film or powder sample holder assembly.

Thank u everyone for your valuable answers

Yes, you can do the PL measurement of powder samples in an liquid material based PL instrument? Basically, most of the people are doing in the same way in case of powder sample.   You can use JASCO FP 6300 which has both thin film as well as powder sample holder.