Yttria-stabilized zirconia thin films by pulsed laser deposition: Microstructural and compositional control

The ns-laser ablation characteristics of tetragonal 3YSZ versus cubic 8YSZ have been investigated to minimize a transfer of particulates in the pulsed laser deposition process. 3YSZ is significantly less prone to the exfoliation of μm-sized fragments than 8YSZ due to its enhanced fracture toughness, which allows the deposition of particulate-free films in a fluence range of 1.2-1.5 J/cm². The influence of the PLD process parameters on the film microstructure and stoichiometry have been investigated with respect to the growth of dense 3YSZ layers with adequate adhesion to the c-cut sapphire single crystals. Dense 3YSZ films are obtained below a threshold pressure of ∼0.025 mbar. At 600 °C polycrystalline layers with a preferential (1 0 1) and (0 0 1) orientation and a columnar microstructure are formed while deposition at room temperature yields uniform amorphous layers. Strongly oxygen deficient films of the metastable t′′ phase are obtained at a low background pressure of 10^-3 mbar. The meta phase films exhibit a low activation energy of 0.77 ± 0.02 eV and an enhanced d.c. electrical conductivity, e.g. 9 × 10^-5 S/cm at 400 °C, comparable or even higher than for 8YSZ films and bulk at temperatures up to 500 °C.