Absorbed wavelength from Kubelka-Munk plot and the experimental values of the absolute band gap energy E_{\mathrm{g}} obtained from different graphic methods for double perovskite \mathrm{Sr}_{2}\left(\mathrm{Co}_{1-x} \mathrm{Fe}_{x}\right) \mathrm{TeO}_{6}
| Sample | \mathrm{Sr}_{2} \mathrm{CoTeO}_{6} | x=0.25 | x=0.5 | x=0.75 | \mathrm{Sr}_{2} \mathrm{FeTeO}_{6} |
|---|---|---|---|---|---|
| \lambda_{\text {abs }} / \mathrm{nm} | 320(2) | 398(2) | 430(2) | 438(2) | 441(2) |
| Direct (h v \times F(R))^{2} | 3.86(2) | 2.95(2) | 2.78(2) | 2.48(2) | 2.74(2) |
| Indirect (h v \times F(R))^{1 / 2} | 3.09(3) and 1.4(3) | 2.23(3) | 1.96(3) | 1.76(3) | 1.87(3) |
| E_{\mathrm{g}} | 3.88(3) | 3.11(3) | 2.88(3) | 2.83(3) | 2.81(3) |
| Transition gap-energy | Direct | Direct | Direct | Direct | Direct |