Preparation of multicomponent rare earth based oxide charges

In this study we describe a relatively facile synthetic approach for the production of multicomponent oxide charges as the precursors of quaternary barium-rare earth-copper selenides BaRECuSe3, 3 , which, in turn, are of interest as promising thermoelectric materials. The starting reagents were initially prepared, including cleaning of the surface of elemental copper and annealing the rare earth oxides RE2O3 2 O 3 in a high-temperature furnace. A mixture of double, ternary and quaternary oxide charges was prepared by dissolving the stoichiometric ratios of the starting reagents RE2O3:2Cu:2Ba(NO3)2 2 O 3 :2Cu:2Ba(NO 3 ) 2 (RE = La, Nd, Gd, Dy, Ho, Y, Er, Tm, Yb, Lu), CeO2:Cu:Ba(NO3)2, 2 :Cu:Ba(NO 3 ) 2 , Pr6O11:6Cu:6Ba(NO3)2 6 O 11 :6Cu:6Ba(NO 3 ) 2 or Tb4O7:4Cu:4Ba(NO3)2 4 O 7 :4Cu:4Ba(NO 3 ) 2 in nitric acid. The Ce-based oxide charge was obtained in the presence of H2O2 2 O 2 as a reducing agent to improve solubility in nitric acid. Then, cocrystallization of crystalline hydrates, followed by their dehydration, and destruction of the resulting (oxo)nitrate salts, and dispersion of the final polycrystalline samples were performed. According to the powder X-ray diffraction data, topochemical reactions led to the formation of heterometallic oxides BaxREyCuzOn, x RE y Cu z O n , BaREO3, 3 , BaCuO2 2 and RE2CuO4. 2 CuO 4 . The developed synthetic approach allows to obtain the target phase of orthorhombic selenides BaRECuSe3 3 of three structural types BaLaCuS3, 3 , Eu2CuS3 2 CuS 3 and KZrCuS3 3 with high yields in a relatively short period of time and at lower temperatures in comparison to the previously used synthetic methods.