Aluminum nitride (AlN) ceramics are attractive materials for microelectronic packaging due to its high thermal conductivity, low dielectric constant and good matching of thermal expansion coefficient [1-4]. However, it is difficult to sinter AlN due to its strong covalent bonding. Densification of AlN powder has been attempted by various techniques. For full densification, rare earth and/or alkaline earth oxides are often added as sintering aids during the fabrication of AlN ceramics . To investigate the effect of microstructure on the thermal properties and sintering behaviour, commercially available AN powder (Grade H, Tokuyama Co. Ltd., Japan) was sintered pressureless by using commercially available Sm203 and Yb203 powders (purity > % 99, Treibacher Industrie, AG, Austria ) as sintering additives and graphene as a secondary phase to improve the thermal properties.
The powder mixture was milled by plenatory ball mill in ethanol for 1.5 hours at 300 cycles / min. Then, the ethanol in the slurry was evaporated. After drying, the powders were pressed by handpress at 50 MPa to obtain pellets. The pellets were cold isostatically pressed (CIP’ed) under 200 MPa. The specimens were then placed into a BN crucible and sintered at 1800 — 1860oC in a graphite furnace with a flowing nitrogen gas.
The heat capacities of the samples were measured by DSC (NETZSCH STA 449F3) whereas the thermal diffusivities of the samples were measured by laser flash technique (Netzsch-LFA 457). The sintered samples were characterized by employing XRD, SEM and TEM techniques. XRD patterns of the samples were recorded using a (Rigaku Rint 2200, Tokyo, Japan) monochromatic CuKα radiation. Scanning electron microscope (SEM) investigations were carried out using a ZEISS SUPRA 50 VP microscope. For TEM investigations 200 kV field emission TEM (JEOL JEM-2100F) equipped with STEM high angle annular dark field (STEM-HAADF) detector (Model 3000, Fischione), electron energy loss spectrometer (EELS) and energy filter (Gatan TM GIF Tridiem), and energy dispersive spectrometer (EDS) (JEOL JED-2300T) was used.
Three different liquid phase addition caused to obtain different intergranular phase formation resulting in a decrease in the thermal diffusivity of the materials with the addition of Yb203 (Fig 1a). When the micstructure was investigated with STEM HAADF (Fig 1 (b, c and d)), the grain boundary intergranular films found to have a very different behaviour. In this study, property-microstructure realtionship for AlN ceramics and AlN-graphene composites will be presented as a function of different sintering addities, different sinterin conditions and heat treatment procedures.
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To cite this abstract:Servet Turan, Alper Cinar, Pinar Kaya; Microstructure-Thermal Conductivity Relationship in Pressureles Sintered AlN Ceramics for Energy Applications. The 16th European Microscopy Congress, Lyon, France. https://emc-proceedings.com/abstract/microstructure-thermal-conductivity-relationship-in-pressureles-sintered-aln-ceramics-for-energy-applications/. Accessed: May 26, 2020
EMC Abstracts - https://emc-proceedings.com/abstract/microstructure-thermal-conductivity-relationship-in-pressureles-sintered-aln-ceramics-for-energy-applications/