Destabilization of the 6H-SrIrO3 polymorph through partial substitution of zinc and lithium

We report on the destabilization of the 6H-SrIrO3 polymorph through partial substitutions of zinc and lithium for iridium to form perovskites. The perovskites crystallize in the orthorhombic space group Pbnm: SrIr1-xZnxO3 is found for 0.25 <= x <= 0.33, while SrIr1-xLixO3 is found only for x=0.25. The Zn and Li ions are randomly distributed in the B-site lattice. Analysis shows that the perovskite stabilization is not driven by changes in average ionic size but rather is due to destabilization of the face-sharing octahedra that are present in 6H-type SrIrO3. Magnetic susceptibility measurements show Curie-Weiss behavior, with relatively large temperature independent contributions, and that the iridium atoms have low effective moments, 0.52 to 1.08 mu(B) per Ir. The resistivity of SrIr0.67Zn0.33O3, characterized by Mott variable range hopping type semiconducting behavior, indicates that substituted Zn ions introduce significant disorder into the system. SrIr0.75Li0.25O3 has a significant linear contribution to the specific heat at low temperatures.