Mechanical twinning and crack nucleation in lithium niobate
Single-crystal, multidomain specimens of ferroelectric lithium meta-niobate have been plastically deformed by compression in the temperature range 1150 to 1250° C.
Subsequent examination of the specimens shows that deformation occurs by twinning on a (10¯12) [¯1011] system. The nucleation of microcracks at twin-band intersections has been commonly observed and a nucleation mechanism, based on the observation that the ferroelectric polarity of the twin band is always opposite to that of the matrix, is proposed.
Measurements of the critical resolved shear stress for twinning afford a partial explanation of the observation that the crack-susceptibility of the material is greater ina-axis crystals than in those grown on thec-axis.
KeywordsPolymer Lithium Shear Stress Lithium Niobate Crack Nucleation
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