Table 4: Atomic percent of elements obtained by XPS analysis of CBS, CBP, and bulk reference. Number of measured points for each sample is indicated inside parenthesis. <DL indicate amounts less than the detection limit of the instrument.

O1s Ca2p P2s Sr3d Al2p F1s Si2p CBS (2) <DL <DL <DL CBP (5) <DL <DL Bulk (5)