Phase separation and crystallization in sodium lanthanum phosphate glasses induced by electrochemical substitution of sodium ions with protons.

Electrochemical substitution of sodium ions with protons (alkali-proton substitution; APS), and the injection of proton carriers was applied to sodium lanthanum phosphate glasses. A clear and homogeneous material was obtained for a glass of composition 25NaO1/2-8LaO3/2-66PO5/2-1GeO2 following APS, with a resulting proton conductivity of 4 × 10(-6) S cm(-1) at 250 °C. The glass underwent phase separation and crystallization at temperatures >255 °C, forming a highly hygroscopic and proton conducting H3PO4 phase in addition to LaP5O14 and other unidentified phases. A glass of composition 25NaO1/2-8LaO3/2-67PO5/2 underwent phase separation and crystallization during APS, forming both H3PO4 and LaP5O14 phases. Sodium lanthanum phosphate glasses are prone to phase separation and crystallization during APS unlike the previously reported NaO1/2-WO3-NbO5/2-LaO3/2-PO5/2 glasses. The phase separation was explained by a reduction in viscosity following APS and the introduction of protons, which exhibit high field strength. Thus, phase separation and crystallization of glasses during APS was difficult to avoid. An approach to suppress phase separation is discussed.

Surface relief hologram formed by selective SiO2 deposition on soda-lime silicate glass.

We propose the fabrication of surface relief holograms via selective SiO2 deposition on soda-lime silicate glass substrates. Initially, the original hologram was recorded on an azobenzene photosensitive polymer film coated on the soda-lime silicate glass by irradiation with a conventional continuous wave Ar+ laser with a wavelength of 514.5 nm. The hologram was transferred to the soda-lime silicate glass surface via a corona discharge treatment as an index modulation hologram, which was created by partial substitution of protons for sodium ions during the corona discharge treatment in air. After the corona discharge treatment, the polymer film was removed from the substrate. The diffraction efficiency of the index hologram on the soda-lime silicate glass was estimated to be 5.8 × 10-2% at a wavelength of 532 nm. Finally, the glass substrate was subjected to corona discharge treatment in air with vaporized cyclic siloxane. A surface relief hologram with the diffraction efficiency of 2.3% was successfully fabricated on the soda-lime silicate glass.

Selective Deposition of SiO2 on Ion Conductive Area of Soda-lime Glass Surface.

Selective deposition of SiO2 nanoparticles was demonstrated on a soda-lime glass surface with a periodic sodium deficient pattern formed using the electrical nanoimprint. Positively charged SiO2 particles generated using corona discharge in a cyclic siloxane vapor, were selectively deposited depending on the sodium pattern. For such phenomena to occur, the sodium ion migration to the cathode side was indispensable to the electrical charge compensation on the glass surface. Therefore, the deposition proceeded preferentially outside the alkali-deficient area. Periodic SiO2 structures with 424 nm and 180 nm heights were obtained using one-dimensional (6 µm period) and two-dimensional (500 nm period) imprinted patterns.