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

The new double-layered perovskites, APrNb(2)O(7) (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; RbPrNb(2)O(7) was refined in space group Imma (a = 5.4534(7) Å, b = 22.012(1) Å, c = 5.4549(7) Å) and CsPrNb(2)O(7) in P4/mmm (a = 3.8668(2) Å, c = 11.163(1) Å). (CuCl)PrNb(2)O(7), topochemically prepared by replacement of Rb(+)/Cs(+) with CuCl(+), contains a 2D Cu-Cl network between the PrNb(2)O(7) 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)PrNb(2)O(7), paramagnetic (μ(eff) = 4.020(8)μ(B)) down to 20 K, exhibits antiferromagnet-like behavior below 20 K.