# Structure and Electrical Properties of Carbon-Rich Polymer Derived Silicon Carbonitride (SiCN)
## 3 Results and Discussion
### Investigation of the Carbon Phase
The crystallite size, L\({}_{a}\), increased as the annealing temperatures used in making the samples increased between 1100 \({}^{\circ}\)C and 1600 \({}^{\circ}\)C. L\({}_{a}\) reveals the width of a single sp\({}^{2}\) hybridized carbon crystal unit and analysis of the Raman spectra shows that during the thermal processing, smaller crystallites grow to form larger size with higher degree of structural orderliness. This increase in crystallite size could be linked to kinetics generated within the materials during the annealing process. At 1600 \({}^{\circ}\)C, the crystallite size of the graphitic carbon has grown to ca. 10 nm (from ca. 7.7 nm at 1100 \({}^{\circ}\)C, see Figure 2a). Moreover, a recorded increase in L\({}_{a}\) as a result of increased ceramization temperatures conforms with the work of [PERSON] et al. as well as [PERSON] et al.,  
Figure 1: Raman spectra of the C/SiCN nanocomposites showing the carbon phase of various samples represented by the peak position and band parameters: (**a**) Raman spectrum of the amorphous C/SiCN nanocomposite pyrolyzed at 1100 \({}^{\circ}\)C; (**b**) Raman spectrum of the C/SiCN nanocomposite annealed at 1400 \({}^{\circ}\)C. (**c**) Raman spectrum of the C/SiCN nanocomposite annealed at 1600 \({}^{\circ}\)C.  
who both studied the evolution of the sp\({}^{2}\)-hybridized carbon phase in polymer-derived SiOC ceramics [24, 46]. An improvement in the structural stability of a graphitic material in terms of strength and ductility could also be achieved via nucleation of the sp\({}^{2}\) carbon crystallite size as discussed in a recent study [47]. In the same vein, [PERSON] et al. revealed that a lateral crystallite size, L\({}_{a}\), greater than 7 nm led to improvements in in-plane electrical conductivity, thermal conductivity and tensile strength [48]. Therefore, an increase in L\({}_{a}\) with temperature increases indicate corresponding growth in the degree of graphitization in the monoliths. On the other hand, as the degree of graphitization rises, the G band gains prominence over the defect-prompted D band, resulting in a decline of the integrated ratio of the D and G band with increasing the annealing temperature (see Figure 2a). Figure 2: Parameters from Raman spectroscopy which determine the evolution of the sp\({}^{2}\) hybridized carbon phase in the polymer-derived C/SiCN nanocomposite materials: (**a**) Dependence of crystallite size (L\({}_{a}\)) and integrated ratios of the D and G bands on temperature; (**b**) shift of the G band as a function of the pyrolysis temperature; (**c**) effect of ceramization temperatures on inter-defect distance (L\({}_{D}\)) and defect density (\(\eta_{D}\)); (**d**) growth in crystallite size (L\({}_{a}\)) of the sp\({}^{2}\) hybridized carbon with an increase in average continuous graphene length including tortuosity (L\({}_{eq}\)). The margin of G band peak position shift between the fabrication temperatures of 1100 \({}^{\circ}\)C and 1400 \({}^{\circ}\)C is observed to be much higher than the shift interval noticed from 1400 \({}^{\circ}\)C to 1600 \({}^{\circ}\)C (see Figure 2b), indicating a high crystallization rate between 1100 \({}^{\circ}\)C and 1400 \({}^{\circ}\)C and slow ceramization between 1400 \({}^{\circ}\)C and 1600 \({}^{\circ}\)C. This is an expected outcome as the material thermally transforms from the initial amorphous state (at 1100 \({}^{\circ}\)C) to a crystalline state (at \(\sim\)1400 \({}^{\circ}\)C), but further conversion beyond 1400 \({}^{\circ}\)C became gentle afterward since a margin of the complete crystallization may have been attained around 1400 \({}^{\circ}\)C [49, 50]. The inter-defect distance (L\({}_{\text{D}}\)), average continuous graphene length including tortuosity (L\({}_{\text{eq}}\)) and defect density (\(\eta_{\text{D}}\)) were calculated using Equation (2) [51], Equation (3) [52] and Equation (4) [44] respectively (where \(\tilde{\Lambda}_{\text{L}}\) is 514 nm).