MICROINDENTATION STUDIES ON BAFCL SINGLE-CRYSTALS

The mechanical behaviour of BaFCl single crystals has been investigated by use of Vickers microindentation. The tests performed on (001) and (100) planes show an important hardness anisotropy, higher values being obtained on (100) planes and all being close to that of BaF2. A qualitative investigation of the impressions has established the occurrence of cleavage along {100} planes, whereas slip occurs much more easily along (001) planes. For tests performed on the (001) plane, a quantitative analysis of the indentation cracks yields a very low toughness value. On comparing the BaFCl and BaF2 structures, it is concluded that the chlorine layers introduce a marked anisotropy but do not have the expected weakening effect.