Formation of high-quality, epitaxial La ₂Zr ₂O ₇ layers on biaxially textured substrates by slot-die coating of chemical solution precursors

Crystallization studies were performed of epitaxial La ₂Zr ₂O ₇ (LZO) films on biaxially textured Ni-3at.%W substrates having thin Y ₂O ₃ (10 nm) seed layers. LZO films were deposited under controlled humid atmosphere using reel-to-reel slot-die coating of chemical solution precursors. Controlled crystallization under various processing conditions has revealed a broad phase space for obtaining high-quality, epitaxial LZO films without microcracks, with no degradation of crystallographic texture and with high surface crystallinity. Crack-free and strong c-axis aligned LZO films with no random orientation were obtained even at relatively low annealing temperatures of 850°-950°C in flowing one atmosphere gas mixtures of Ar-4% H ₂ with an effective oxygen partial pressure of P(O ₂)∼10 ^-22 atm. Texture and reflection high-energy electron diffraction analyses reveal that low-temperature-annealed samples have strong cube-on-cube epitaxy and high surface crystallinity, comparable to those of LZO film annealed at high temperature of 1100°C. In addition, these samples have a smoother surface morphology than films annealed at higher temperatures. Ni diffusion rate into the LZO buffer film is also expected to be significantly reduced at the lower annealing temperatures.