Ceramic bead composition

Hello, G4Users,

I need to simulate the disk-type calibration sources from Eckert & Ziegler which consists of an active component in the form of a bead that is fixed inside the plastic capsule. I am having difficulty figuring out the correct chemical composition and density of ceramic beads, which seems to be causing quite a disagreement between data and simulation. If anyone has done a similar simulation and has more information on the ceramic or any hints would be highly appreciated.