Optimization of the tape casting slurries for high-quality zirconia substrates

A cheap and environmental friendly non-aqueous tape casting process for preparing high density ZrO2 ceramic substrates was explored. A binary solvent mixture of ethanol and ethyl acetate -based formula was developed by using castor oil, polyvinyl butyral and dibutyl phthalate as the dispersant, binder and plasticizer, respectively. The influence of dispersant content, binder content and solid loading on the rheological properties of ZrO2 slurries was firstly investigated. It was found that the optimized formulation for dispersant, binder and solid loading was 1 wt%, 4 wt% and 60 wt%, respectively. The flat, flexible and uniform green tapes with a thickness of 200–280 µm and high-quality including high bulk density, uniform pore distribution and low porosity were obtained. After drying and debinding, the green sheets were sintered at 1480 ℃ for 1 h, where ZrO2 ceramics with a relative density of 98% and a dielectric constant being 32 can be achieved. The sintered samples could satisfy the use requirement of the fingerprint identification cover plate.