Two-step pulsed electric current sintering of transparent Al₂O₃ceramics

Abstract

Fully densified Al 2 O 3 ceramics with fine grain size were obtained by pulsed electric current sintering through a two-step heating profile (referred to as TS-PECS). Highly transparent Al 2 O 3 polycrystals with fine grain size (400 nm) were successfully fabricated by the TS-PECS process, namely, sintering at 1000uC for 1 h and followed at 1200uC for 20 min under uniaxial pressure of 100 MPa. Effects of the first step temperature and heating rate were discussed for bulk density, grain size and transparency. The temperature in the first step strongly affects densification and grain growth of Al 2 O 3 . On the other hand, heating rate, even of 100 K min 21 , in TS-PECS does not give significant influences on densification and grain growth of Al 2 O 3 . Inline transmittance at 640 nm in wavelength normalised to 1 mm in thickness is increased by decreasing heating rate even in TS-PECS.

Transparent alumina ceramics densified by a combinational approach of spark plasma sintering and hot isostatic pressing

“…Interestingly, the transparent alumina ceramics prepared by spark plasma sintering (SPS) can reach an even smaller grain size. Grain sizes in the range from 140 to 300 nm were obtained by SPS [10][11][12][13][14][15][16]. However, the transparency in the visible range was low (40-50%) as a result of some residual porosity in densified bodies (the values lie well below the theoretical limit) [13][14][15][16].…”

“…Grain sizes in the range from 140 to 300 nm were obtained by SPS [10][11][12][13][14][15][16]. However, the transparency in the visible range was low (40-50%) as a result of some residual porosity in densified bodies (the values lie well below the theoretical limit) [13][14][15][16]. Higher in-line transmission of about 65% (at a wavelength of 640 nm and a sample thickness of 0.8 mm) was only obtained when extremely high pressure during SPS (400-500 MPa) was applied [10][11][12].…”

Densification and Grain Growth of Large-Sized Polycrystalline Al₂O₃ during a Two-Step Pulsed Electric Current Sintering Process

“…27) Nanko et al used a special two-step PECS technique to fabricate transparent polycrystalline Al 2 O 3 . 6) In this technique, a profile with two temperature-holding steps was used; the temperature of the first stage is smaller than the temperature of the final stage. By using the two-step profile, the densification of the sintering process becomes more effective with less grain growth.…”

Spark Plasma Sintering and Characterization of Graphene Platelet/Ceramic Composites

“…[1,2] However, the brittleness of the ceramics has seriously limited their further applications. [1,2] However, the brittleness of the ceramics has seriously limited their further applications.…”