Deformation restraint of tape-casted transparent alumina ceramic wafers from optimized lamination

Transparent alumina (Al2O3) ceramic wafers are frequently applied in industry, however it is usually difficult to obtain a high-quality transparent alumina ceramic wafer without any deformation. Here we present a non aqueous tape-casting method, which is followed by a presureless vacuum sintering process, to fabricate the transparent alumina ceramic wafers with restrained or eliminated undesired deformation or cracking. By using scanning electron microscope, we observe the microscopic morphologies of green tapes and sintered wafers from various different laminate methods, including cold pressing, cold isostatic pressing, warm pressing, and the combinations of warm pressing plus cold isostatic pressing. We find that the warm pressing pretreatment has an impressive optimization effect on the microscopic morphologies of the green tapes due to the properties of thermoplastic structure in the green tape, and also plays a promotional role in wafer densification process. With the optimized green tapes which are dense and uniform, transparent alumina ceramic wafers with a thickness of 500 mu m and the lateral size of 63 mm x 63 mm without any deformation or cracking were successfully fabricated. We also examine the transmittance properties of the as-prepared wafer, and find that our obtained transparent alumina ceramic wafers without deformation or cracking have no loss of good transmittance in contrast to previous work.