Structure and physical properties for a new layered pnictide-oxide: BaTi2As2O

We have successfully synthesized a new layered pnictide-oxide: BaTi2As2O. It shares similar characteristics with Na2Ti2Sb2O. The crystal has a layered structure with a tetragonal P4/nmm group (a = 4.047(3) angstrom, c = 7.275(4) angstrom). The resistivity shows an anomaly at 200 K, which should be ascribed to an SDW or structural transition. The SDW or structural transition is confirmed by magnetic susceptibility and heat capacity measurements. These behaviors are very similar to those observed in parent compounds of high-T-c iron-based pnictide superconductors, in which the superconductivity shows up when the anomaly due to the SDW or structural transition is suppressed. Therefore, the new layered pnictide-oxide, BaTi2As2O, could be a potential parent compound for superconductivity. It is found that Li+ doping significantly suppresses the anomaly, but no superconductivity emerges so far.