Impact of Li Doping on the Structure and Phase Stability in AgNbO.

The impact of Li doping on the temperature-induced phase transitions in silver niobates AgLiNbO has been investigated using a combination of high-resolution powder neutron diffraction and synchrotron X-ray diffraction. Considering both the cell metric and distortions of the NbO octahedra, estimated by Rietveld refinements, it is shown that the sequence of temperature-induced phases in AgNbO is 2 → → → 4/ → 3̅. This sequence is simpler than that proposed in earlier studies. Evidence is presented for a second-order Jahn-Teller distortion in the phase. At > 0.05, Li doping favors the formation of a rhombohedral phase in space group 3, and such samples display the temperature-induced sequence 3 → → → 4/ → 3̅. Unusual volume changes associated with the phase transitions point to the potential importance of lattice matching in optimizing the properties of thin films of doped AgNbO.