The phase equilibria in the Sb-Sn system – Part I: Literature review.

For several decades, controversial and seemingly contradicting results were published for the Sb-Sn intermetallic system, which led to the construction of different phase diagram versions. Within the investigation of the thermochemistry of Sb-Sn based systems for use as anode materials in Li-ion batteries, many of these uncertainties were resolved through the introduction of the compound Sb 3 Sn 4 (space group R 3 ¯ m , Bi 3 Se 4 prototype), whose crystal structure can be derived as a commensurate ordering from the neighboring incommensurate SbSn crystal structure (space group R 3 ¯ m , distorted NaCl type). Due to the amount of collected literature data and own analyses this work is presented as a two-part series, where Part I describes and assesses the current state of knowledge, while part II reports the new results and consistently resolves the discrepancies between earlier reports and this work. Existing literature data already show that an Sb 2 Sn 3 compound with ordered NaCl structure cannot exist due to the diverging stoichiometry. Direct experimental evidence in favor of the existence of this compound is scarce, but thermal effects that might correspond to its peritectic formation were frequently and consistently observed. Newer results point towards the existence of a compound Sb 3 Sn 4 instead of Sb 2 Sn 3 , but no crystal structure has been reported so far. Claims for further ordered phases lack the support through conclusive X-ray data. The understanding of the Sb-Sn system therefore essentially depends on understanding the complex crystallography of its intermetallic phases. [ABSTRACT FROM AUTHOR]