/doi.org/10.26434/chemrxiv-2023-tqvh2-v2 space group symmetry, as expected for vacancy-𝐹𝑚3𝑚 ordered double perovskites. Since Sn 4+ (0.69 Å) is larger than that of Ti 4+ (0.61 Å), the lattice parameter increases by inserting more tin in the structure, so that all the diffraction peaks shift to lower angles as x in Cs 2 Ti 1-