The interfacial energies of three twin boundaries with low-index boundary planes: prismatic (101⁻0), basal O-terminated (0001), and basal Cr-terminated (0001), and the segregation energies of five doping elements (Ce, Hf, La, Y and Zr) have been calculated as a function of temperature. The static energies at 0 K were obtained through first-principles calculations and the energies at finite temperatures were derived based on the Debye model. The calculation results show that both the interfacial and segregation energies decrease as temperature increases and the segregation energies are found to be proportional to the ionic size mismatch and the interfacial energy. Our combined approaches suggest an efficient and less computationally intensive way to derive grain boundary energetics at finite temperatures.