Bismuth-substituted Sr3Ti2O7 Ruddlesden-Popper oxide prepared by molten salt method with tunable electrical conductivity

The Sr3Ti2O7 Ruddlesden Popper (RP) compound offers promising applications for electronic materials, in which the modification of the electronic band structure of the respective crystal significantly affects its functionalities. The molten salt technique successfully synthesized two-layer Ruddlesden Popper Sr3-xBixTi2O7 (x = 0, 0.0125, 0.025, 0,05, and 0.1) through the A-site cation substitution. The crystal structure analysis indicates that 0.1 mole Bi doping at the Sr site results in higher crystallinity and matches Sr3Ti2O7 RP phase standard data. The Bi3+ doping on the Sr2+ sites aims to increase the number of charge carriers and enhance the electrical conductivity of the compound. The changes in the electronic band structure via substitution with a high valence dopant on strontium cations succeeded in changing the bandgap energy of the synthesized compound. The images of the sintered body show dense pellet samples with sub-micron cubic particles. Electrical conductivity measurements demonstrated that the Bi-doped compounds exhibited a higher electrical conductivity threefold compared with the undoped Sr3Ti2O7 sample. These findings present the simple synthesis method to obtain Bi-doped Sr3Ti2O7 compounds with tunable electrical conductivity.