Destabilization of the 6H-SrIrO ₃ polymorph through partial substitution of zinc and lithium

We report on the destabilization of the 6H-SrIrO ₃ polymorph through partial substitutions of zinc and lithium for iridium to form perovskites. The perovskites crystallize in the orthorhombic space group Pbnm: SrIr _1-xZn _xO ₃ is found for 0.25 ≤ x ≤ 0.33, while SrIr _1-xLi _xO ₃ 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 SrIrO ₃. 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 μ _B per Ir. The resistivity of SrIr _0.67Zn _0.33O ₃, characterized by Mott variable range hopping type semiconducting behavior, indicates that substituted Zn ions introduce significant disorder into the system. SrIr _0.75Li _0.25O ₃ has a significant linear contribution to the specific heat at low temperatures.