Formation of La{sub 4-x}M{sub x}Ni{sub 3}O{sub y} solid solutions (M = Ca, Sr, Ba)

Doping of mixed oxides is known to be capable of substantially modifying their physicochemical properties. For example, partial substitution of strontium for lanthanum in semiconducting La{sub 2}CuO{sub 4} results in the formation of the La{sub 1.85}Sr{sub 0.15}CuO{sub 4} solid solution, which exhibits superconducting properties. Over the past few years, significant effort has been devoted to the investigation of La{sub 2-x}Sr{sub x}NiO{sub y} nickelates, which are isostructural to high-temperature cuprate superconductors and can be used as parent compounds for producing superconductors. The formation of La{sub 4-x}Mg{sub x}Ni{sub 3}O{sub y} solid solutions was reported. At the same time, no data are available on the possibility of preparing analogous solid solutions with other alkaline-earth elements. In this work, the authors report the results on the synthesis of La{sub 4-x}M{sub x}Ni{sub 3}O{sub y} solid solutions (M = Ca, Sr, Ba), their composition ranges, and some physicochemical properties. The choice of subject for the investigation was determined by the chemical and structural similarity of the solid solutions in question to the well-known high-temperature cuprate superconductors and by the high metallic conductivity of La{sub 4}Ni{sub 3}O{sub 10}.