Processing and characterization of sol–gel fabricated mixed metal aluminates

Nanocrystalline lanthanum aluminate (LaAlO3, LAP) and Sr-substituted LAP ceramics were synthesized by sol-gel processes using mixtures of inorganic salts of the respective elements. The metal ions, generated by dissolving metal nitrates or acetates in acetic acid and/or water were complexed by 1,2-ethanediol to obtain the precursor for LAP. The XRD patterns of the LaAlO3 and La1-xSrxAlO3-d (x < 0.50) ceramic sintered at 1000 C were almost identical with the perovskite LAP composition. The phase transformations, composition and microstructural features in the gels and polycrystalline samples were studied by thermal analysis (TG/DTA), powder X-ray diffraction analysis (XRD), infrared spectroscopy (IR), scanning electron microscopy (SEM), energy dispersive X-ray analysis (EDX) and inductively coupled argon plasma emission spectroscopy (ICP). The quality of the resulting products (homogeneity, crystallisation temperature, grain size and grain size distribution, etc.) of the chimie douce synthetic route is discussed.