Synthesis and characterization of the rare-earth hybrid double perovskites: (CH3NH3)2KGdCl6 and (CH3NH3)2KYCl6
27th September 2017
Abstract
Two hybrid rare-earth double perovskites, (CH3NH3)2KGdCl6 and (CH3NH3)2KYCl6, have been synthesized by a solution evaporation method and their structures deter- mined by variable temperature single crystal X-ray diffraction. The diffraction results show that at room temperature both perovskites adopt a rhombohedral structure with R¯3m symmetry, as found previously for (MA)2KBiCl6, and lattice parameters of a = 7.7704(5) Å and c = 20.945(2) Å for (MA)2KGdCl6 and a = 7.6212(12) Å and c = 20.742(4) Å for (MA)2KYCl6. Both phases exhibit a rhombohedral to cubic phase transition on heating to ∼435 K for (MA)2KYCl6 and ∼375 K for (MA)2KGdCl6. 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)2KGdCl6, could exhibit magnetic ordering at low temperatures.