Topochemical synthesis of three-dimensional perovskites from lamellar precursors

A topochemical route to nondefect, three-dimensional perovskites from lamellar Dion-Jacobson and Ruddlesden-Popper precursors was demonstrated. The method involves reduction of one of the ions (in this case Eu³⁺) in the precursor phase and concomitant loss of oxygen. CsEu₂Ti₂NbO₁₀, a three- layer Dion-Jacobson compound, was ion-exchanged to AEu₂Ti₂NbO₁₀ (A = Na, Li) and reduced in hydrogen to form the SrTiO₃-type perovskites AEu₂Ti₂NbO₉. Similarly, K₂Eu₂Ti₃O₁₀, a three-layer Ruddlesden-Popper compound, underwent divalent ion exchange to form the Dion-Jacobson compounds A(II)Eu₂Ti₃O₁₀ (A(II) = Ca, Sr) and M(II)Eu₂Ti₃O₁₀ (M(II) = Ni, CU, Zn), which were reduced in hydrogen to perovskite-type A(II)Eu₂Ti₃O₉ and M(II)Eu₂Ti₃O₉, respectively. The A(II) and Eu²⁺ ions of A(II)Eu₂Ti₃O₉ remain ordered, while A-site disordering occurs in the other perovskites. In all cases, the anisotropic texture of the layered precursors is retained in the product perovskite phase.