## 3 Results and Discussion
### Analysis of Phase Content Based on Raman Spectra  
The main Raman band (shift) identified from the Raman spectroscopy measurements for each specified phase used to prepare the samples was compared with previous studies [11; 12; 13; 14; 15]. Table 3 shows the Raman shift or band (cm\({}^{-1}\)) for measured samples in this work and the published reference materials. Figure 3 illustrates the Raman spectra for the initial phases used to prepare the binary samples.  
The observations made for the samples measured with Raman spectroscopy show that a change in phase content in the binary samples system may have a corresponding effect on the relative intensity of the peaks. They are presented in Figures 4-8. Section 2.3.3 briefly describes the information that can be obtained from the intensity of a Raman peak for Raman spectroscopy measurements. Figures 4-8 are,  
\begin{table}
\begin{tabular}{c c c c c c c c c} \hline \hline \multicolumn{2}{c}{**Initial Phase**} & \multicolumn{3}{c}{**XRD Phase**} & \multicolumn{3}{c}{**XRF Calculated Phase Composition (wt\%) and Elemental Data**} \\ \multicolumn{2}{c}{**Composition (wt\%)**} & \multicolumn{3}{c}{**Composition (wt\%)**} & \multicolumn{3}{c}{**XRF Calculated Phase Composition (wt\%) and Elemental Data**} \\ \hline Al\({}_{2}\)O\({}_{3}\) & CaS & Al\({}_{2}\)O\({}_{3}\) & CaS & Al\({}_{2}\)O\({}_{3}\) & CaS & Ca & S & Al \\
10 & 90 & 8 & 92 & 15 & 85 & 46.81 & 37.44 & 8.16 \\
20 & 80 & 18 & 82 & 24 & 76 & 42.08 & 33.66 & 12.66 \\
30 & 70 & 28 & 72 & 34 & 66 & 36.26 & 29.01 & 18.23 \\
60 & 40 & 58 & 42 & 57 & 43 & 23.55 & 18.83 & 30.41 \\
70 & 30 & 72 & 28 & 69 & 31 & 17.28 & 13.82 & 36.38 \\
90 & 10 & 91 & 9 & 89 & 11 & 6.28 & 5.02 & 46.95 \\ \hline \hline \end{tabular}
\end{table}
Table 2: Initial sample composition, XRD and XRF analyses for binary aluminum oxide-calcium sulphide phases of Al2O3–CaS.  
Figure 3: Raman spectra for initial phases of Al\({}_{2}\)O\({}_{3}\), C12A7, CaS, C3A, MA, and CA used for preparing the binary phase samples.  
\begin{table}
\begin{tabular}{c c c c} \hline \hline
**Phase** & **Measured Peaks [Raman Shift, cm\({}^{-1}\)]** & **Reference [Raman Shift, cm\({}^{-1}\)]** & **Reference** \\ \hline CaS & 156–160 s, 190–200 \(m\), 478 \(w\) & 160 \(s\), 185 \(m\), 215 (\(\pm\)15), 485 (\(\pm\)10) \(w\) & [12] \\ C12A7 & 517 \(s\), 781 \(m\), 314 \(m\) & 312–333 \(m\), 516–517 \(m\), 772 \(m\), 779 \(m\) \(m\) & [13; 15] \\ C3A & 766 \(s\), 512 \(m\), & 756–760 \(s\), 506–508 \(m\) & [13; 15] \\ Al\({}_{2}\)O\({}_{3}\) & 420 \(s\), 386 \(m\), 760 \(m\) & 413–420 \(s\), 375–382 \(m\), 748–751 \(m\) & [11] \\ MgO-Al\({}_{2}\)O\({}_{3}\) & 412 \(s\), 674 \(m\), 773 \(m\) & 409–412 s, 76–7772 m, 666–674 \(m\) & [14] \\ \hline \hline \end{tabular}
\end{table}
Table 3: Reference and measured Raman shift (cm\({}^{-1}\)) for starting phases of CA, CaS, C12A7, C3A, Al\({}_{2}\)O\({}_{3}\), and MgO-Al\({}_{2}\)O\({}_{3}\) (where s is strong, m is medium, and w is weak).  
therefore, used to qualitatively explain how the relative intensity of the peaks associated with a specific phase can be used to estimate the particular phase content present in the samples.  
Figure 4: Raman spectra for CaS (_i_), MA (_v_) and binary MA–CaS phase sample with CaS content, where (_ii_) 80 wt. %, (_iii_) 60 wt. %, and (_iv_) 20 wt. %.  
Figure 5: Raman spectra for CaS (_i_), CA (_v_) and binary CA–CaS phase sample with CaS content, where (_ii_) 80 wt. %, (_iii_) 60 wt. %, and (_iv_) 20 wt. %.  
Figure 6: Raman spectra for CaS (_i_), C12A7 (_v_) and binary CaS–C12A7 phase sample with CaS content, where (_ii_) 80 wt. %, (_iii_) 60 wt. %, and (_iv_) 20 wt. %.  
Figure 7: Raman spectra for CaS (_i_), C3A (_v_) and binary CaS–C3A phase sample with CaS content, where (_ii_) 80 wt. %, (_iii_) 60 wt. %, and (_iv_) 20 wt. %.