Deformation during Vickers nanoindentation in highly oriented nonlinear optical Ba_2TiGe_2O_8 crystalline layers at glass surface(<Feature>Fracture and Related Phenomena of Glasses)

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Transparent surface crystallized glasses consisting of c-axis oriented nonlinear optical Ba_2TiGe_2O_8 crystalline layers (〜10 μm) at the surface of 40BaO・20TiO_2・40GeO_2 glass are prepared, and their deformation behaviors are examined from the load/unload displacement curves obtained with the Vickers nanoindentation technique. It is found that the surface crystalline layers deform easily in small loadings during Vickers nanoindentations in comparison with the precursor glass with a homogeneous random glass structure. The surface crystalline layers subjected to the penetration depth of h = 0.5 μm show a large elastic recovery of 〜70% compared with that (49%) in the precursor glass. The sliding (displacement) of about 0.02 μm is observed immediately after the stop of the loading with a loading speed of 5 μm/s in the surface crystallized samples. The present study suggests that the deformation behaviors of the surface Ba_2TiGe_2O_8 crystalline layers in the crystallized glass might be closely related to the assemblage state of highly oriented crystals, in particular, the bonding (i.e., the degree of the adhesion ) among c-axis oriented crystals might be weak.
社団法人日本セラミックス協会の論文
2008-08-01