High-Pressure Synthesis, Structure, and Magnetic Properties of Ge-Substituted Filled Skutterudite Compounds; LnxCo4Sb12−yGey, Ln = La, Ce, Pr, and Nd

Hiroshi Fukuoka

doi:10.3390/cryst7120381

Abstract

A series of new Ge-substituted skutterudite compounds with the general composition of LnxCo4Sb12−yGey, where Ln = La, Ce, Pr, and Nd, is prepared by high-pressure and high-temperature reactions at 7 GPa and 800 °C. They have a cubic unit cell and the lattice constant for each compound is 8.9504 (3), 8.94481 (6), 8.9458 (3), and 8.9509 (4) A for the La, Ce, Pr, and Nd derivatives, respectively. Their chemical compositions, determined by electron prove microanalysis, are La0.57Co4Sb10.1Ge2.38, Ce0.99Co4Sb9.65Ge2.51, Pr0.97Co4Sb9.52Ge2.61, and Nd0.87Co4Sb9.94Ge2.28. Their structural parameters are refined by Rietveld analysis. The guest atom size does not affect the unit cell volume. The Co–Sb/Ge distance mainly determines the unit cell size as well as the size of guest atom site. The valence state of lanthanide ions is 3+.

Highlights

The filled skutterudite compounds have attracted much attention after the finding of the anomalous superconductivity of PrOs4 Sb12 [1]
The high-pressure and high-temperature reactions are very effective to prepare new skutterudite compounds, including superconductors [2,3,4,5], and a great many filled skutterudite compounds have been reported for the widespread combination of the elements by the high-pressure techniques
High-pressure and high-temperature reactions provide a new series of Ge-substituted filled skutterudite compounds, Lnx Co4 Sb12−y Gey, where Ln = La, Ce, Pr, and Nd

Summary

Introduction

The filled skutterudite compounds have attracted much attention after the finding of the anomalous superconductivity of PrOs4 Sb12 [1]. It has a cage structure composed of corner-sharing MX6 octahedra and large guest atoms A, which are situated in the cages, where A, M, and X are electropositive elements (mainly alkaline earth and rare earth elements), transition metals (group 8 and 9), and electronegative elements (mainly group 15), respectively. The high-pressure and high-temperature reactions are very effective to prepare new skutterudite compounds, including superconductors [2,3,4,5], and a great many filled skutterudite compounds have been reported for the widespread combination of the elements by the high-pressure techniques. Bromine filled skutterudite has been reported [9]

Methods

Results

Conclusion