KBr Pelleting :

in this methods, a small amount of sample (~ 1  -  2 mg)  is mixed and ground along with about hundred times its mass of potassium bromide. The combination is transferred to an evacuuable die, to erase the moisture and then a high pressure is applied to yield a transparent pellet. It is put in a suitable holder and the whole assembly is placed in the line of the infrared beam.

Figure: Die assembly for making KBr pellets

Thin films: The IR spectrum of a thin film could be acquired through placing a sample of the film in a appropriate holder, such as a card along with a slot for the sample window.  This technique  is  quite  useful  in  the  calibration  of  the  instrument  along with  a  standard  like polystyrene for which the bands are accurately known.