N. Bunjes et al. Journal of Non-Crystalline Solids 353 (2007)1567-1576 BF 100nm 100nm B c 100 Fig. 5. Bright field image and elemental distribution images of Si, C, and B of 5c thermolyzed at 1400C/2 h/Ar and subsequently annealed at 1600C/ 5 h/Ar elemental maps where bright areas show the presence and Fig. 6(a)shows different sets of diffraction rings which dark areas the absence of a particular element. In this can be assigned to SiC and a BNCx phase way, the distribution of Si, C and b within the sample Annealing of 5c at 1700C for 5 h in an argon atmo- could be visualized as shown in Fig. 5. The grains observed sphere leads to formation of larger SiC crystals compared in the bright field micrographs seem to correspond toto those observed after the heat treatment at 1600C Ring bright areas in the Si map. This indicates a high Si concen- patterns in the EDP (Fig. 6(b) become slightly sharper and tration within the grains. The surrounding matrix phase show the absence of further crystalline phases apart from appears dark in the Si map. Nevertheless, the presence of SiC and BNCx at this temperature. A typical microstructure Si cannot be excluded by this analysis because small con- and elemental maps of Si, C, and B are shown in Fig. 7 centrations of Si are difficult to detect. In the carbon map From the bright field image, the crystal size can be esti- the brightness is seemingly inverted. The grains(see BF) mated to range from about 25 to 125 nm with an average are clearly darker than the matrix. Therefore, the carbon diameter of 37.5 nm. The shape of the grains is mostly glob. concentration within the matrix must be higher than that ular. As was already observed for the 1600C sample, the within the grains. The boron map shows similar features crystal grains are composed of silicon carbide. In the Si or with dark areas at grain positions and brighter areas C map, they can be observed as bright or gray areas, respec between the grains. In contrast to the carbon distribution, tively. The larger crystals show striped contrast features however, grain boundaries are more distinct in the boron which are caused by stacking faults due to the formation map. In both C and B map, the distribution of the elements of Sic polytypes in the grains as can be shown by hrtEM within the matrix phase seems to be homogeneous and selected area diffraction. The surrounding matrix con- The phase content of this sample was furthermore ana- tains carbon, and boron(and nitrogen) with a C concentra- red by electron diffraction. The EDP presented in tion significantly higher than in SiC.elemental maps where bright areas show the presence and dark areas the absence of a particular element. In this way, the distribution of Si, C and B within the sample could be visualized as shown in Fig. 5. The grains observed in the bright field micrographs seem to correspond to bright areas in the Si map. This indicates a high Si concen￾tration within the grains. The surrounding matrix phase appears dark in the Si map. Nevertheless, the presence of Si cannot be excluded by this analysis because small con￾centrations of Si are difficult to detect. In the carbon map the brightness is seemingly inverted. The grains (see BF) are clearly darker than the matrix. Therefore, the carbon concentration within the matrix must be higher than that within the grains. The boron map shows similar features with dark areas at grain positions and brighter areas between the grains. In contrast to the carbon distribution, however, grain boundaries are more distinct in the boron map. In both C and B map, the distribution of the elements within the matrix phase seems to be homogeneous. The phase content of this sample was furthermore ana￾lyzed by electron diffraction. The EDP presented in Fig. 6(a) shows different sets of diffraction rings which can be assigned to SiC and a BNCx phase. Annealing of 5c at 1700 C for 5 h in an argon atmo￾sphere leads to formation of larger SiC crystals compared to those observed after the heat treatment at 1600 C. Ring patterns in the EDP (Fig. 6(b)) become slightly sharper and show the absence of further crystalline phases apart from SiC and BNCx at this temperature. A typical microstructure and elemental maps of Si, C, and B are shown in Fig. 7. From the bright field image, the crystal size can be esti￾mated to range from about 25 to 125 nm with an average diameter of 37.5 nm. The shape of the grains is mostly glob￾ular. As was already observed for the 1600 C sample, the crystal grains are composed of silicon carbide. In the Si or C map, they can be observed as bright or gray areas, respec￾tively. The larger crystals show striped contrast features which are caused by stacking faults due to the formation of SiC polytypes in the grains as can be shown by HRTEM and selected area diffraction. The surrounding matrix con￾tains carbon, and boron (and nitrogen) with a C concentra￾tion significantly higher than in SiC. Fig. 5. Bright field image and elemental distribution images of Si, C, and B of 5c thermolyzed at 1400 C/2 h/Ar and subsequently annealed at 1600 C/ 5 h/Ar. N. Bunjes et al. / Journal of Non-Crystalline Solids 353 (2007) 1567–1576 1571