Synthesis and Characterization of the Rare-Earth Hybrid Double Perovskites: (CH₃NH₃)₂KGdCl₆ and (CH₃NH₃)₂KYCl₆

High Resolution Image Download MS PowerPoint Slide Two hybrid rare-earth double perovskites, (CH 3 NH 3 ) 2 KGdCl 6 and (CH 3 NH 3 ) 2 KYCl 6, have been synthesized by a solution evaporation method and their structures determined by variable temperature single-crystal X-ray diffraction. The diffraction results show that at room temperature both perovskites adopt a rhombohedral structure with R 3̅ m symmetry, as found previously for (MA) 2 KBiCl 6, and lattice parameters of a = 7.7704(5) Å and c = 20.945(2) Å for (MA) 2 KGdCl 6 and a = 7.6212(12) Å and c = 20.742(4) Å for (MA) 2 KYCl 6 . Both phases exhibit a rhombohedral-to-cubic phase transition on heating to ∼435 K for (MA) 2 KYCl 6 and ∼375 K for (MA) 2 KGdCl 6 . Density functional calculations on the rhombohedral phase indicate that both materials have large direct band gaps, are mechanically stable, and, in the case of (MA) 2 KGdCl 6, could exhibit magnetic ordering at low temperatures.