Preparation process of large-size high-purity ceramic substrate

The invention relates to a preparation process of a large-size high-purity ceramic substrate, which is characterized in that micron alpha-aluminum oxide is used as a main phase material, nano gamma-aluminum oxide is used as a sintering aid, proper additives such as a solvent, a dispersing agent, a binder and a plasticizer are added, and the ceramic substrate is prepared by a method of hot pressed sintering after tape casting. According to the preparation process, thin green sheet laminations are obtained through tape casting, then glue is discharged, gradient pressure is applied to multiple layers of green sheets, and hot pressed sintering is carried out. Due to the fact that the technology that the green body pieces are firstly subjected to glue discharging and then subjected to high-temperature hot pressing sintering is adopted, organic additives in the green body pieces can be completely discharged in the glue discharging process, the defects of air holes, gaps and the like and gas residues caused by glue