Journal Article thermoelectrics 1D tetrahedral networks Gases Research Support, Non-U.S. Gov't SrFeO2.5 bismuth antimony telluride complex oxide electronic structures ferroelectricity fractional delta-doping graphene layered structures magnetoelectric coupling multiferroicity optical spectroscopy perovskite oxides superlattices thermopower thin films topotactic phase transformation transition metal oxides two-dimensional transport van der Waals epitaxy