Influence of sintering temperature and pressure on crystallite size and lattice defect structure in nanocrystalline SiC

Abstract

Microstructure of sintered nanocrystalline SiC is studied by x-ray line profile analysis and transmission electron microscopy. The lattice defect structure and the crystallite size are determined as a function of pressure between 2 and 5.5 GPa for different sintering temperatures in the range from 1400 to 1800°C. At a constant sintering temperature, the increase of pressure promotes crystallite growth. At 1800°C when the pressure reaches 8 GPa, the increase of the crystallite size is impeded. The grain growth during sintering is accompanied by a decrease in the population of planar faults and an increase in the density of dislocations. A critical crystallite size above which dislocations are more abundant than planar defects is suggested.

Characterization of defect structures in nanocrystalline materials by X-ray line profile analysis

“…in Fig. 4b in [114], which indicates that strain broadening of the profiles is caused by dislocations.…”

“…Nanocrystalline SiC offers very high strength either as a binding phase in diamond composites or as a single phase material even at high temperatures [114]. Ultrafine grained bulk SiC samples are usually fabricated from nanopowders by sintering at high pressures and temperatures.…”

“…Ultrafine grained bulk SiC samples are usually fabricated from nanopowders by sintering at high pressures and temperatures. It is expected that the microstructure of sintered SiC can be tailored by the proper selection of these two parameters [114].…”

“…For the quantitative characterization of lattice defect structure and crystallite size in nanostructured SiC samples, the X-ray patterns of the initial powder and the sintered specimens were evaluated by the eCMWP fitting method [114]. Typical examples of the fitting for the samples sintered at 5.5 GPa and temperatures of 1400 C and 1800 C are shown in Fig.…”

Defect-Related Physical-Profile-Based X-Ray and Neutron Line Profile Analysis

“…[29] The FWHM values are shown in Williamson-Hall plots after sintering at 1800°C at 2 and 5. [24] Authors called this plot the ''Wagner [25] plot,'' which is similar to the Williamson-Hall plot.…”