Controlled evolution of morphology and microstructure in laser interference-structured zirconia

Tape-cast pseudo-cubic zirconia pellets were surface irradiated by two coherent interfering high-power short-pulse Nd:YAG laser beams. The interfering beams of the third harmonic with a wavelength of 355 nm of a 2.5-ns Q-switched laser produced a line-like intensity distribution with a periodic distance of 3.3 μm due to the selected angle between the beams. The resulting nonuniform surface heating produced a microstructure consisting of ultrafine-grained zirconia with a grain size of about 10 nm within the top 100-200 nm depth of the treated surface region due to the high cooling rates during short-pulse laser processing (up to 10 ¹⁰ K/s). The surface morphology closely followed the microperiodic heat treatment provided by the interfering laser beams. The pore size distribution within the periodic surface morphology ranged from a few nanometers to a maximum of half of the periodic line distances.