Influence of processing parameters on the densification and the microstructure of pure zinc oxide ceramics prepared by spark plasma sintering

Abstract

This is an author's version published in: http://oatao.univ-toulouse.fr/23777 ARTICLE INFO ABSTR ACT Keywor ds:ZnO Spark plasma slntering Nanopartlcles CeramJcs MicrostructureDue to the sensitivity of nanopowders and the challenges in controlling the grain sire and the density during the sintering of ceramics, a systernatic study was proposed to evaluate the densifi cation and the microstructure of ZnO oeramics using sparlc plasma sintering technique. Cornrnercially available ZnO powder was dried and sin tered at various parameters (ternperature (400-900 °C), pressure (250--850 MPa), atmosphere (Air/Vacuum) etc.). High pressure sintering is desirable for rnaintaining the nanostructure, though it brings a difficulty in obtaining a fully dense ceramic. Whereas, increasing the ternperature from 600 to 900 •c results in fully den sifi ed ceramics of about 99% which shows tn have big impact on the grain size. However, a high relative density of 92% is obtained at a ternperature as low as 400 •c under a pressure of 850 MPa. The application of pressure during the holding tirne seems tn lower the grain sire as compared to ceramics pressed during initial stage (room ternperature).

Thermoelectric properties of ZnO ceramics densified through spark plasma sintering

“…The commercial and synthesized ZnO powders were densified using SPS already descrbed in the previously published paper [32] using 8 and 20 mm inner diameter tungsten carbide and graphite dies. The molds were lined with 0.2 mm thick graphite foil (PERMA FOIL®Toyo Tanso).…”

“…The displacement ratio of both samples showed two peaks: sharp peaks at 100 300s (room temperature) and broad peaks at 600 1000s (300 600°C). The first peak could be attributed to the rearrangement of grains by rolling due to applied pressure at room temperature [32,35,36]. The second peak could be due to the densification of the ceramics at high temperature, with grains diffusing with neighbouring grains.…”

“…The second peak could be due to the densification of the ceramics at high temperature, with grains diffusing with neighbouring grains. The influence of sintering temperature on ceramics prepared through commercial powder (CCP) has been published [32].…”

Porosity properties of porous ceramic substrates added with zinc and magnesium material

“…The porosity ratio is then similar for all the four samples except for DD3Z(t)+50%ZnO where the size of the pores is the maximum. This last different value for the pore size is due to the initial state of overlapping materials of ceramic powder and zinc, where it was found that the decomposition of zinc at high temperatures works to break the inter-linkages between the ceramic powders and creates spaces on the surface of the sample and inside [30].…”

The Role of Sacrificial and/or Protective Layers to Improve the Sintering of Electroactive Ceramics: Application to Piezoelectric PZT-Printed Thick Films for MEMS

“…Alumina powder placed on both sides of ZnO samples were also used to insulate ZnO from the current. Insulation prevents the influence of the electric field on the ZnO grains, which affects the reactivity and diffusion during sintering [60]. Also noteworthy is the innovative approach based on sacrificial Al 2 O 3 or ZrO 2 powders reported by C. Manière et al to fabricate complex shape materials with a controlled microstructure.…”