The sensor in the mar345 detector (image plates from Fuji) is coated with
BaFBr(0.85)I(0.15):Eu2+. thickness of the material about 100 microns.

The phosphor in the marccd  is Gd2O2S of approx 400 um thickness coupled
to a fibre optics taper.

The mar555 detector uses amorphous Selenium for conversion of X-rays
into electrons with a thickness of approx. 300 um.

Personal communication of Claudio Klein.
Thanks to marxperts for sharing those informations