Transparent, surface crystallised glasses containing a ferroelectric LaBGeO5 crystalline phase were successfully prepared through a two-step heat treatment in air (e.g. 670°C+750°C) for 25La2O3·25B2O3·50Ge O2 glass. The temperature of maximum nucleation rate was determined to be 670°C, from differential thermal analysis, which is consistent with the glass transition temperature. The LaBGeO5 crystalline phase was confirmed to be formed within the surface region to a depth of about 60 μm. The bulk crystallised glasses, obtained by heat treatments around the crystallisation temperature, were opaque. The second harmonic intensity from the transparent crystallised glasses was of the order of 11100 of that for α-quartz SiO2. Transparent surface crystallised glasses with La1-xGdxBGeO5 crystalline phases were also fabricated through a two-step heat treatment.
|Number of pages
|Physics and Chemistry of Glasses
|Published - 2000