Synthesis and characterization of the rare-earth Dion–Jacobson layered perovskites, APrNb2O7 (A = Rb, Cs and CuCl)

Abstract

The new double-layered perovskites, APrNb₂O₇ (A = Rb, Cs) have been prepared by a high temperature ceramic method. Rietveld refinement of X-ray powder diffraction data confirmed the orthorhombic and tetragonal structures, respectively; RbPrNb₂O₇ was refined in space group Imma (a = 5.4534(7) Å, b = 22.012(1) Å, c = 5.4549(7) Å) and CsPrNb₂O₇ in P4/mmm (a = 3.8668(2) Å, c = 11.163(1) Å). (CuCl)PrNb₂O₇, topochemically prepared by replacement of Rb⁺/Cs⁺ with CuCl⁺, contains a 2D Cu–Cl network between the PrNb₂O₇ slabs (orthorhombic space group Pbam, a = 7.7328(6) Å, b = 7.7113(4) Å and c = 11.6706(3) Å). The parent compounds both show paramagnetic behavior μ_eff (Rb) = 3.34(1)μ_B and μ_eff (Cs) = 3.60(2)μ_B while the (CuCl)PrNb₂O₇, paramagnetic (μ_eff = 4.020(8)μ_B) down to 20 K, exhibits antiferromagnet-like behavior below 20 K.