Gd-Nd Solubility in the (Gd,Nd)-Sr-Ru-Cu-O System

The recent great interest on (Gd1212) due to the coexistence of magnetic order and superconductivity in the same cell, has induced investigation on the whole RE1212 family where other Rare Earth elements (RE) are used. Being RE1212 isostructural to RE123 our interest focuses on Nd, that forms the highest RE123 compound and presents a slightly larger ionic radius than Gd and a lower magnetic moment. Pure Nd1212 is characterized by great structural disorder then, to investigate Gd1212 properties variation, only a partial substitution of Nd ions in Gd sites in the Gd1212 cell may be attempted. The possibility of Gd-Nd substitution and the solid solubility limit have been investigated by the synthesis of powders with a nominal composition. Phases formation has been checked by XRD. Experimental results indicate a limit for Nd solubility in Gd1212 of less than 20%. A corresponding limit of about 2% for Gd solubility in Nd1212 has also been observed. More accurate measurements, in the range are needed to better estimate this limit. Variation of the cell parameters have been observed for both phases, both showing shorter c axes and an orthorhombic structure for 1:1 molar ratio mixtures. Thermal properties have been studied by TG-DTA, revealing a substantial insensibility of Nd-rich phase to the presence of the Gd-rich one in contrast with a visible decrease of Gd-rich phase peritectic melting temperature in dependence of Nd-rich phase addition. Further investigations will be needed to clarify all the processes involved in the melting-resolidification cycle.