Mechanical properties of single crystalline and glassy lithium triborate

Mechanical properties of LiB 3 O 5 single crystal plates with different orientation as well as of glass with the same composition have been investigated. The nano‐ ( H ) and microhardness ( H M ), the reduced Young's modulus ( E r ) and the crack behaviour of the samples were studied. Both hardness and Young's modulus of glass appeared smaller in comparison to corresponding single crystal data ( H ∼ 7 – 8 GPa, H M ∼ 6 GPa, E r ∼ 70 – 80 GPa for glass and H ∼ 10 – 15 GPa, H M ∼ 6 –11 GPa, E r ∼ 93 – 155 GPa for single crystal). H , E r , and the plane of crack propagation proved orientation‐dependent. Cracks in the glass sample were not observed up to 0.49 N microindentation load, whereas for the single crystal the cracks appeared already at 0.098N. In single crystals the observed cleavage planes {211} and/or {412} are oriented nearly parallel to planes of B‐O rings. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)