Facile preparation of apatite-type lanthanum silicate by a new water-based sol–gel process

In recent years, apatite-type lanthanum silicates ([Ln10−x(XO4)6O3–1.5x] (X = Si or Ge)) have been studied for use in SOFC (solid oxide fuel cells), at low temperature (600–800 °C), due to its ionic conductivity which is higher than that of YSZ (Yttrium Stabilized Zirconia) electrolyte. For this reason they are very promising materials as solid electrolyte for SOFCs. Synthesis of functional nanoparticles is a challenge in the nanotechnology. In this work, apatite-type lanthanum silicate nanoparticles were synthesized by a water-based sol–gel process, i.e., sol–gel technique followed by chemical precipitation of lanthanum hydroxide on the gel of the silica. Na2SiO3 waste solution was used as silica source. Spherical aerogel silica was prepared by acid catalyzed reaction, followed by precipitation of lanthanum hydroxide to obtain the precursor of apatite-type lanthanum silicate. Powders of apatite-type lanthanum silicate achieved from the precursor were characterized by thermal analysis, X-ray diffraction (XRD), scanning electron microscopy (SEM) and specific surface area measurements (BET). The apatite phase was formed at 900 °C.

Figure optionsDownload as PowerPoint slideHighlights
► We use a Na2SiO3 waste solution as source of Si.
► We present a simple, rapid and low temperature method of lanthanum silicate apatite preparation.
► TEOS, a high cost reagent, was successfully substituted by a cheap price Na2SiO3, to obtain pure La9.56(SiO4)6O2.33 lanthanum silicate apatite.