Line patterning of (Sr,Ba)Nb2O6 crystals in borate glasses by transition metal atom heat processing

Some NiO-doped Bi2O3,La2O3–SrO–BaO–Nb2O5–B2O3 glasses giving the formation of strontium barium niobate Sr0.5Ba0.5Nb2O6 (SBN) crystals with a tetragonal tungsten–bronze structure through conventional crystallization in an electric furnace have been developed, and SBN crystal lines have been patterned on the glass surface by heat-assisted (250–300 °C) laser irradiation and scanning of continuous-wave Nd:YAG laser (wavelength: 1064 nm). The surface morphology and the quality of SBN crystal lines are examined from measurements of confocal scanning laser micrographs and polarized micro-Raman scattering spectra. The surface morphology of SBN crystal lines changes from periodic bump structures to homogeneous structures, depending on laser scanning conditions. It is suggested that the line patterned at the laser irradiation condition of laser power P=1 W and of laser scanning speed S=1 μm/s in 2NiO–4La2O3–16SrO–16BaO–32Nb2O5–30B2O3 glass has a possibility of the orientation of SBN crystals along the laser scanning direction. The present study demonstrates that the transition metal atom heat processing (i.e., a combination of cw Nd:YAG laser and Ni2+ ions) is a novel technique for spatially selected crystallization of SBN crystals in glass.