Lanthanum borogermanate glass-based active dielectrics

Abstract Favorable properties of stillwellite-like LaBGeO 5 stimulated many attempts to realize them on an industrial scale. However, the growth of stillwellite single crystals is problematic and, because of strong structural anisotropy, dense stillwellite ceramics were not synthesized to date. Unique properties of crystalline LaBGeO 5 may be realized via bulk or grain-oriented crystallization of lanthanum borogermanate (LBG) glasses. Nucleation, bulk and surface crystallization including grain-oriented crystallization of LBG glasses are briefly reviewed. Dependence of crystallization behavior of LBG glasses on the synthesis conditions was found to be closely linked with alumina impurities that suppress texture forming but improve glass-forming ability. The latter offers an opportunity to obtain LBG-based glasses of optical quality, containing more than 30 mol% rare-earth oxides, for laser and magneto-optical applications. A wide range of active dielectrics in the LBG system covering non-linear optical nano-structures, planar wave guides and textures with excellent pyroelectric activity are expected to be developed.