Effect of calcination temperature on the degree of polymorphic transformation in Y2SiO5 nanopowders synthesized by sol–gel method

• High purity Y2SiO5 nanopowders were synthesized merely at 900 °C by sol–gel method.
• Widespread inter-polymorphic phase transition from X1 to X2 occurred at 1250 °C.
• X2 polymorph purified on increase in temperature up to 1500 °C.
• In either of the polymorphs, grain refinement occurred with increase in temperature.

Due to its excellent chemical and physical stability, Y2SiO5 is a strong candidate material for host matrix for luminescent materials, high dielectric constant insulators, and protective coatings for ceramic matrix composites such as C/SiC, C/C and C/C-SiC. In this work, Y2SiO5 ceramic powders have been synthesized by simple and reliable sol–gel method using tetraethyl orthosilicate (TEOS) and yttrium nitrate hexahydrate Y(NO3)3·6H2O as precursor substances and 0.1 g of HCl as a catalyst. Sol–gel derived powders were subjected to different calcination temperatures. The fabricated powders after calcination resulted in the formation of ultra-high purity nanopowders Y2SiO5 (X1 polymorph) merely at 900 °C, which is lower than that reported in previous studies. The powders were analyzed by X-ray diffraction (XRD), thermogravimetry–differential scanning calorimetry (TGA–DSC), scanning electron microscopy (SEM), and Brunauer–Emmett–Teller (BET) specific surface area analysis method. Widespread inter-polymorphic transformation into X2 form occurred at temperature above 1200 °C. Systematic studies have been performed on inter-polymorphic and intra-polymorphic transition behavior and the associated changes in the grain sizes based on the XRD results.