Synthesis of nanocrystalline La2O3–Y2O3–ZrO2 solid solutions by hydrothermal method: A crystal growth and structural study

Well-size-distributed nanopowders of lanthana–yttria–zirconia ternary oxide were synthesized by hydrothermal method. The effects of La2O3 on crystal growth and phase transition of YSZ nanocrystallite were investigated in detail with 8La2O3–8YSZ as an example. X-ray Diffraction (XRD), Thermogravimetric analysis (TG) and Differential Scanning Calorimeter analysis (DSC), Fourier Transform Infrared Spectroscopy (FT-IR), Scanning Electron Microscopy (SEM) and High Resolution Transmission Electron Microscopy (HRTEM) were applied to characterize the phase formation, thermal decomposition and morphology of nanopowders. The XRD results indicate that 8La2O3–8YSZ is composed of both the face-centered cubic (ZrO2) and pyrochlore (La2Zr2O7, LZ) structures. The average crystallite size obtained from TEM observation is 5–7 nm. The sample has a specific surface area of 201.2 m2 g−1, which is obviously higher than that of 8YSZ (145.9 m2 g−1). Moreover, the effective activation energy (Q) of crystal growth of 8La2O3–8YSZ and 8YSZ can be divided into two stages: below 900 °C, Q8YSZ=5.68 kJ mol−1 and Q8La2O3−8YSZ=1.91kJmol−1; in the range of 900–1300 °C, Q8YSZ=53.2 kJ mol−1 and Q8La2O3−8YSZ=81.2kJmol−1.

► Uniformly distributed nanopowders in ternary oxide lanthana–yttria–zirconia system were synthesized by hydrothermal method.
► Crystalline spheres have high-developed surface area.
► The phase transition of pyrochlore La2Zr2O7 occurred at about 1000 °C.
► The activation energy can be divided into two ranges at 900 °C due to phase transition.