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Recently, we have developed the borosilicate glass, in which ZrO2 phase is singly crystallizable, and has found an emissive monoclinic ZrO2 dendrites in the resulting GCs. In order to promote the formation of monoclinic phase, we have examined the effect of substitution of alumina Al2O3 for ZrO2 in the precursor glass composition, i.e., 15Na2O–(15 − x)ZrO2–xAl2O3–30B2O3–40SiO2. It was found that the substitution of small amount of Al2O3 (x = 1) gave a positive effect, i.e., increase in the amount of monoclinic phase and decrease in the crystal size. Furthermore, the substitution improved the internal quantum-yield. On the other hand, the further substitution (x ≥ 2) provided the decrease in amount of the monoclinic phase.

Photoluminescent properties of amorphous zinc phosphate glass, containing Sn2 + as an emission center, were investigated. Varying the chemical composition changed both the excitation and emission properties. The redox reaction that occurred during melting was found to affect both valences of transition metal and Sn cations to change the emission property of the Sn2 +-containing glass. We have also examined the emission property of substituted SnO–ZnO–P2O5 glass, and demonstrated that the emission color can be tailored by chemical composition to obtain blue, white, and red. It is notable that the quantum efficiency value of the present RE-free glass is comparable to that of crystal phosphor such as MgWO4. We have, therefore, emphasized that transparent inorganic glass phosphor will be one of the fascinating emitting materials adoptable to future strong LED light source.

The authors investigate the structural change of a ZnO–P 2 O 5 sintered matrix for the preparation of SnO-doped zinc phosphate (SZP) glass using a platinum crucible. Heat treatment of zinc oxide and ammonium phosphate at 800 °C causes the formation of a Zn 2 P 2 O 7 -like species, which is effective in preventing damage to the platinum crucible. Although the thermal property of the glass was affected by added Al 2 O 3 , Al 2 O 3 hardly affects the quantum efficiency of the SZP glass phosphor. This process is important for the fabrication of contamination-free phosphate glass using ammonium phosphate as a starting material.

ZnO surface crystallized glass-ceramics were fabricated using K 2 O-CaO-ZnO-B 2 O 3 -SiO 2 -Al 2 O 3 glass system. Precipitation of Zn-containing oxide crystallites was affected by the chemical composition of borate glass, especially the amount of Al 2 O 3 . Substitution of SiO 2 for B 2 O 3 brought selective crystallization of ZnO without precipitation of α-Zn 3 B 2 O 6 . ZnO-precipitated glass-ceramics showed surface crystallization with submicron-sized crystallites, which assured transparency of these glass-ceramics. The obtained glass-ceramic shows free exciton emission, which is similar to emission of ZnO single crystal.

Surface crystallization of metastable α-Zn 3 B 2 O 6 was observed in ZnO-B 2 O 3 -CaO-K 2 O-Al 2 O 3 glass after conventional heat treatment. Precipitation of α-Zn 3 B 2 O 6 with high orientation degree in the transparent glass–ceramics was confirmed by XRD measurement. Transmission electron microscope image showed that crystalline rods of α-Zn 3 B 2 O 6 were precipitated from the surface of the glass–ceramics with the crystalline orientation of (1 − 2 1) direction. Although the strongly oriented phase was observed in the glass–ceramics, the polarization direction was not strong from the crystal that can bring strong second harmonic generation (SHG). SHG measurement using a powder sample showed that the 2nd optical nonlinearity of α-Zn 3 B 2 O 6 glass–ceramics was comparable to that of α-SiO 2 .

We examined the laser-induced crystallization to form the fresnoite type Ba 2 TiGe 2 O 8 crystal line patterns in transition metal ion doped BaO–TiO 2 –GeO 2 glass. Ba 2 TiGe 2 O 8 crystal line was written in 0.6FeO–33.3BaO–16.7TiO 2 –50GeO 2 glass by continuous wave yttrium–aluminum–garnet (YAG) laser irradiation. We obtained polarization dependence of Raman spectra in crystal line pattern. Second harmonic generation (SHG) indicated unique fringe patterns from Ba 2 TiGe 2 O 8 crystal lines.

The BaO–TiO 2 –SiO 2 crystallized glass containing Ba 2 TiSi 2 O 8 crystal phase was examined using X-ray diffraction (XRD) measurement and Maker fringe technique. It has been found that the crystallized glasses with a composition of close to the stoichiometric Ba 2 TiSi 2 O 8 showed bulk crystallization, whereas other crystallized glasses with non-stoichiometric composition of Ba 2 TiSi 2 O 8 showed surface crystallization. The parameter Δ T , the difference in temperature between the crystallization onset and the glass transition temperature, strongly affects the crystallization behaviors of the present BTS glasses. The 30BaO–20TiO 2 –50SiO 2 transparent surface crystallized glass with strong c -oriented Ba 2 TiSi 2 O 8 phase showed its second-order non-linear optical constant, d 33 = 6.1 pm/V.

The glasses with the compositions of 21.25RE2O3–63.75MoO3–15B2O3 (RE: Sm, Gd, Dy) were prepared and the formation of β′-RE2(MoO4)3 ferroelectrics was confirmed in the crystallized glasses obtained through a conventional crystallization in an electric furnace. The features of the glass structure and crystallization behavior were clarified from measurements of Raman scattering spectra. Continuous-wave Nd:YAG laser with a wavelength of 1064 nm (laser power: 0.6–0.9 W, laser scanning speed: S = 1–16 μm/s) was irradiated to 10.625Sm2O3–10.625Gd2O3 (or Dy2O3)–63.75MoO3–15B2O3 glasses, and the structural modification was induced at the glass surface. At the scanning speed of S = 10 μm/s, crystal lines consisting of β′-Gd2−xSmx(MoO4)3 or β′-Dy2−xSmx(MoO4)3 crystals were patterned on the glass surface. It was found that those crystal lines have the surface morphology with periodic bumps. At S = 1 μm/s, it was found that crystal lines consist of the mixture of paraelectric α-Gd2−xSmx(MoO4)3 and ferroelectric β′-Gd2−xSmx(MoO4)3 crystals, indicating the phase transformation from the β′ phase to the α phase during laser irradiation. Homogeneous crystal lines with β′-RE2(MoO4)3 ferroelectrics have not been written in this study, but further research is continuing.

A continuous wave (cw) Nd:YAG laser operating at a wavelength of 1064 nm irradiated Sm 2 O 3 - and Dy 2 O 3 -doped glasses under various irradiation conditions in the systems of Ln 2 O 3 –BaO–B 2 O 3 (Ln:Sm and Dy), and non-linear optical β-BaB 2 O 4 (β-BBO) crystals lines are formed at the surface of glass substrates. It is proposed from the azimuthal dependence of second harmonic intensity that β-BBO crystal lines might be single crystals with the c -axis orientation along the laser scanning direction. The photoluminescence spectra indicate that Sm 3+ ions are incorporated into β-BBO crystal lines. The present study proposes that cw Nd:YAG laser irradiation to glass containing Sm 3+ and Dy 3+ is a novel technique for a spatially selected crystallization in glass.

The optical non-linearity of transparent glass-ceramic materials in K 2 O–Nb 2 O 5 –GeO 2 and K 2 O–Nb 2 O 5 –TeO 2 systems has been investigated using electric-field-induced second harmonic (EFISH) and Maker fringe techniques. For the tellurite glass-ceramics, which show an SHG property without any electric treatment like thermal poling, the SH signal is relatively low and insensitive to the applied field. On the other hand, the germanate glass-ceramics consisting of nanocrystalline K 3.8 Nb 5 Ge 3 O 20.4 phase have a good transparency, and the apparent susceptibility of second order non-linearity is linearly increased with instantaneous applied field of various frequencies up to 1 kHz. The non-linearity constant corresponding to the third-order χ (3) is estimated by Maker fringe profiles and increased by three times after nanocrystallization over the precursor glass.

A continuous-wave Nd:YAG laser operating at a wavelength of 1064 nm is used to irradiate BaO–Sm2O3–TeO2 glasses under various conditions (laser power: 0.5–0.7 W, irradiation time: 1–60 s), and the formation, behavior and morphology of crystal-dots and lines consisting of the Sm2Te6O15 phase are examined. Crystal-dots with a corn-like shape are formed at the surface of the glasses. The diameters of crystal-dots are 3–45 μm and their lengths (depths) toward the interior of glasses are 50–110 μm. The size of crystal-dots depends on laser power, laser irradiation time and Sm2O3 content. The diameter and length of crystal-dots increase almost linearly with the cube root of laser irradiation time t1/3, suggesting that the growth of crystal-dots in the YAG laser-induced crystallization is controlled by diffusion of constituent ions. Crystal-lines with a width of ∼10 μm are also written by scanning the YAG laser at a speed of 20–30 μm s−1. A model of YAG laser-induced crystallization is proposed.

Transparent nanocrystallized glasses consisting of Er2Te5O13 nanocrystals (∼100 nm size) have been prepared in 10BaO · 10Er2O3 · 80TeO2, and load/unload displacement curves at room temperature (humidity 53%) have been measured in the penetration depth of ht=200–600 nm using a Vickers nanoindentation technique. The values (4.0–9.4±0.1 GPa) of universal (dynamic) hardness (Hu) in the nanocrystallized glasses are larger than those (Hu=2.7–6.5±0.1 GPa) in the precursor glass and are slightly smaller than those (Hu=4.4–9.7±0.1 GPa) in the opaque crystallized glass consisting of Er2TeO6 crystals. The elastic recoveries during unloading are 0.53–0.61, being almost the same as those in the precursor and opaque crystallized glasses. The elastic Ue and plastic Up deformation energies at ht=500 nm in the nanocrystallized glasses are estimated to be Ue=106 and Up=91±3 kJ mol−1, respectively. These values are larger than those of the precursor glass (Ue=83 and Up=57±3 kJ mol−1), suggesting that the deformation energy during loading in TeO2-based glasses is largely increased due to nanocrystallization. The main origin of plastic deformation at ht

The formation mechanism of ferroelastic Ba2TiGe2O8 crystals in 30BaO · 15TiO2 · 55GeO2 glass and second order optical non-linearity of transparent crystallized glasses have been examined. It has been confirmed that the BaTiGe3O9 crystalline phase is initially precipitated and acts as a nucleation site for the formation of the Ba2TiGe2O8 crystalline phase. Transparent surface crystallized glasses consisting of grain-oriented Ba2TiGe2O8 crystals have been successfully fabricated by means of heat-treatments (690–750 °C, 3 h) for the first time, and second harmonic (SH) generation has been clearly observed, demonstrating that Ba2TiGe2O8 is a non-linear optical crystalline phase. The SH intensity of transparent crystallized glasses (bulk state) with crystalline layers of ∼10 μm thickness is comparable to that of Z-cut α-quartz single crystal with a thickness of 0.6 mm. The SH intensity of Ba2TiGe2O8 crystals (powdered state) prepared through solid-state reaction is about 130 times as large as that of pulverized α-quartz.

A CW YAG laser with a wavelength of 1064 nm and with a power of 1 W has been used to irradiate samarium tellurite glasses with the compositions of 10RO·10Sm 2 O 3 ·80TeO 2 (R=Mg, Ba) at room temperature for 30–60 s. It is found from polarized optical microscopy and from X-ray diffraction (XRD) analyses that crystalline dot patterns with sharp refractive index changes are formed by laser irradiation. The diameters of the spherical dots in the glasses with BaO and MgO are about 50 and 150 μm, respectively. It has been proposed that the crystallization of a nanocrystalline Sm 2 Te 6 O 15 phase is induced through the absorption of irradiated YAG laser by the Sm 3+ ions. This is the first finding of crystalline dot patterning induced by infrared CW YAG laser irradiation in glass.

We have demonstrated that IR halogen lamp heat-treatment induces crystallization at the surface of the CuO-doped glass, in which selective crystallization of TiO 2 was observed after heat-treatment. X-ray diffraction pattern of the glass-ceramic prepared IR heat-treatment showed crystallization of TiO 2 without significant loss of optical transparency. Photocatalytic decomposition of organics by TiO 2 glass-ceramic heat-treated using an IR furnace shows a value similar to that of the glass-ceramics heat-treated using an electric furnace, which indicates that TiO 2 can be crystallized at the surface of the bulk material by IR furnace heat-treatment. The present technique is thought to be useful for the preparation of homogeneous surface crystallized glass-ceramics without optical loss.

Fabrication of Bi-free transparent TiO 2 glass-ceramics was attained by substitution a mixture of alkaline earth oxide and ZnO for Bi 2 O 3 . It is suggested that ZnO, which can play a role of both intermediate and network modifier, is important for the substitution. Observed particle size of precipitated anatase in the glass-ceramics was several nanometers enough to possess high transparency. It was found that diffraction intensity of metastable anatase in XRD patterns of glass-ceramics increases with increasing ZnO-concentration with heat-treatment at T g + 50 K. The obtained results show that substitution of Bi 2 O 3 by thermodynamic approach is effective for glass materials as well as glass-ceramics.