Chemically deposited La2Zr2O7 (LZO) thin films are crucial for coated conductor production since they transfer the texture from a highly biaxially textured nickel substrate to the YBCO superconducting layer and act as nickel diffusion barriers. The misfit of LZO with respect to Ni is 7.6%. The LZO buffer layers studied in this work were deposited on biaxially textured Ni-5at%W substrates by chemical solution deposition (CSD) using the same precursor starting solutions and were annealed at temperatures ranging from 600 to 1000°C for 1 h. Samples were studied by scanning electron microscopy (SEM), X-ray diffraction (XRD) and transmission electron microscopy (TEM) in plan-view and cross-section. By combined TEM and XRD investigations on the same samples we found a clear difference in the microstructure of the LZO thin films: (i) a nanocrystalline state for T < 800°C with grains 5-10 nm in size (ii) and a polycrystalline state for T > 800°C with an average grain size of up to 200 nm. Thus, the LZO grain size is much smaller than the Ni grain size and the LZO buffer layers are highly biaxially textured, but no epitaxial growth occurs. Grain growth started at 800°C and nanovoid formation and growth occurred during the grain growth process. The nanovoid size was determined to be 10-20 nm and small-angle grain boundaries were observed in the LZO buffer layers. The facetting of the LZO grain boundaries play an important role in the grain growth process, samples annealed at higher temperatures had less strongly facetted grain boundaries than at lower temperatures. On top of the LZO buffer layers YBCO thin films were deposited by PLD and CSD yielding critical current densities of >1 MA/cm2 at 77 K.