Strength distribution and fracture analyses of LiNbO3 and LiTaO3 single crystals under biaxial loading

Experimental results showed a significant difference in strength, LiNbO3 being weaker than LiTaO3. No apparent SCCG and no volume effect on strength were found. A different distribution to Weibull behaviour was observed in LiNbO3. Fractography showed differences in the fracture patterns, due to the different cutting orientation of the two investigated materials with respect to the loading plane. New cleavage planes were identified as {10.1} for LiNbO3 and {12¯.3} for LiTaO3. Fracture surfaces of LiNbO3 revealed surface damage, which may be responsible for the lower strength compared to LiTaO3.