Papers by Author: Hirokazu Masai

Abstract: In-situ observation of inelastic light scattering of boson region in glassy Ba2TiGe2O8 (BTG) was performed during heating process. The in-situ boson observation revealed structural relaxation below glass-transition temperature in the as-quenched sample, suggesting the nanometric structural heterogeneity. Relation of the boson behavior to crystallization tendency is also discussed.

Abstract: We examined photoluminescent (PL) and afterglow properties in bazirite (BaZrSi3O9) phases with Sr2+-, Sn4+-, Ge4+-, and Ti4+-impurities, in order to elucidate effect of the impurity-addition on these properties. The bazirite phases studied showed blue PL and afterglow regardless of sort of the impurities. Origin of PL and afterglow emission in the bazirite phase is also discussed.

Abstract: Correlation between surface crystallization behavior of BaO-TiO2-GeO2 (BTG) glass and the thermal stability parameter measured by Differential Thermal Analysis (DTA) was examined. We have proposed normalized thermal stability ΔTnorm of the BTG glass using crystallization temperature (Tx), glass transition temperature (Tg), and melting temperature (Tm). It was found that surface crystallization occurred in the BTG glass possessing ΔTnorm (= (Tx-Tg)/Tm) value larger than 0.08. Compared ΔTnorm value of bulk state with that of powdered state, it has been revealed that Ba2TiGe2O8 was precipitated independently of thermal stabilities whereas BaTiGe3O9 or BaGe4O9 was precipitated in precursor glasses possessing high surface stability.

Abstract: Crystallization behavior of the fresnoite-type Ba2TiGe2O8 (BTG) with a large optical nonlinearity has been examined in the BaO-TiO2-GeO2 glass thin film fabricated by a RF sputtering technique and the corresponding glass (same composition of thin film, i.e., 28BaO-22TiO2-50GeO2). Both the glass thin film and the corresponding glass were crystallized by the heat-treatment, keeping a good transparency. Initial formation of BTG phase followed by the BaGe4O9 phase was confirmed in the both glass samples. In addition, the BTG crystallites in the both glass samples indicated the preferential (211) orientation. Crystallization behavior confirmed in this study was quite different from the previous study about the 30BaO-15TiO2-55GeO2 glass.