MICROHARDNESS OF SINGLE-CRYSTALS OF THE CALOMEL FAMILY

Microhardness of Hg2Cl2, Hg2Br2 and Hg2I2 single crystals has been measured on (001) and (110) faces using the indenter after Vickers. It has been found that the microhardness of the first two homologues differs only slightly whereas the iodide is considerably softer: by about 20% on the (001) face and by about 30% on the (110) face. The average microhardness value, calculated from the values obtained on gradually rotating the indenter over 360° on the (001) face, is for Hg2Cl2 and Hg2Br2 practically equal to the microhardness of NaCl (20.3 and 19.4 compared to 19.6 · 107 Pa). The average microhardness of the (110) face is for Hg2Cl2 and Hg2Br2 about 2 × lower and for Hg2I2 about 2.6 × lower than that of the (001) face. In the case of Hg2Cl2 the microhardness of the (001) face has been also calculated from crystallochemical parameters and the results have been found to be in good agreement with the value obtained experimentally for the orientation of the indenter's diagonal parallel to the [100] direction, where the data is the least influenced by the elasticity of the sample (16.6 compared to 18.6 · 107 Pa). Copyright © 1979 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim