Scanning electron microscopy sintered ceramics

Scanning Electron Microscopy, SEM, showed mini-cracks but with a grain size of only 10 um compared with a well sintered Mg-PSZ ceramic showing a larger grain size of about 50 um. 

The microstructure observation of the sintered ceramics surface was performed by means of scanning electron microscopy (SEM, JEOL JSM 6400, Japan). The crystalline phase of sintered ceramics was identified by X-ray diflfaction (XRD, RIGAKU D/max 2.B) with CuKa radiation (X=l. 541SA at 40 kV and 30 mA) and scanned from 20° to 70° with scanning speed of 4°/min. The bulk densities of the sintered pellets were measured by the Archimedes method. The dielectric constant ( ,) and the quality factor values (Qxf) at microwave frequencies were measured using the Hakki-Coleman dielectric resonator method which had been modified and improved by Courtney The dielectric resonator was positioned between two brass plates. Microwave... 

Figure 1.17 Scanning electron microscopy image of the 8 mol% Ce02-stabilized ZrOz ceramic after spark plasma sintering [210].

Fig. 5. Scanning electron microscopy picture of sintered at 1200°C ceramics being compacted at 40 MPa.

Nanocrystalline yttria (Y2O3) powders with most suitable characteristics for the fabrication of yttria crucibles were synthesized by the sol-gel method [85]. The combustion synthesis method was used starting with high-purity (99.9%) yttrium nitrate hexahydrate and citric acid. Different fuel to oxidant (citric acid/nitrate) ratios (0.25, 0.5, 0.75, 1.0, and 1.1) were tested. These mixtures were heated at 373 K until a viscous gel was formed, and its decomposition into powder formation was realized by thermal treatment at 473 K for 3 h. In all mixtures, yttria powders were obtained by thermal treatment at 1073 K. Scanning electron microscopy (SEM) showed that these powders were porous, whereas high-resolution transmission electron microscopy (HRTEM) revealed that they consist of randomly oriented cuboidal nanocrystallites with an average crystallite size of about 17-30 nm. In order to obtain dense ceramics, the powders were compacted as pellets at 120 MPa and were sintered at 1673 K. Pellets with a sintered density as high as 98-99% of the theoretical density could be obtained from powders prepared with fuel to oxidant ratios (/ ) of 0.75 and 1.0. 

Minor concentrations of foreign compositions at grain boundaries and three-grain junctions in a sintered ceramic can be characterized using transmission electron microscopy (TEM) and electron diffraction, scanning transmission electron microscopy (STEM) with EDS or electron energy loss spectroscopy (EELS), and AES. ... 

---