Energetically benign synthesis of lanthanum silicate through "silica garden" route and its characterization

Abstract

Lanthanum silicate synthesis through "silica garden" route has been reported as an alternative to energy intensive milling procedure. Under optimum conditions lanthanum chloride crystals react with water glass (sodium silicate) to produce self generating hollow lanthanum silicate precipitation tube(s) (LaSPT). The micro tubes are irregular, thick, white coloured and amorphous but are hierarchically built from smaller tubules of 10-20 nm diameters. They retain their amorphous nature on being heated up to 600 degrees C beyond which crystallization starts. The major phase in the LaSPT heated at 900 degrees C is La2Si2O7. "As synthesized" LaSPT is heterogeneous and comprises non stoichiometric phases. The exterior and interior surfaces of these tubes are remarkably different in their morphology and chemical composition. LaSPT sintered at 1200 and 1300 degrees C show fair amount of ionic conductivity. (C) 2017 Elsevier B.V. All rights reserved.