Ionic complexes in liquid Li–K–Pb alloys

Abstract

An experimental study of the volumetric properties of the ternary system Li–K–Pb in the liquid state was carried out. The density (ρ) and volumetric thermal expansion coefficient (β) were measured for alloys of the following stoichiometric compositions: Li₃KPb₄, LiKPb₂, LiK₃Pb₄, LiKPb, Li₄K₃Pb₄, Li₄KPb₂, Li₁₆K₃Pb₇ and Li₅KPb₃. The experiments employed a contactless method of irradiating samples with a narrow beam of gamma quanta in the range from the liquidus temperatures of the alloys to 1000 K with an uncertainty of ρ and β values of 0.6–0.9 % and 4–7 %, respectively. Based on the obtained results, recommended temperature dependences of the studied properties were compiled and the relative excess molar volume was calculated. The latter was found to be negative for all alloys and anomalously large in absolute value, about 20–30 %. According to experimental studies of binary Li–Pb and K–Pb alloys, such significant volumetric compression may indicate the presence of short-range chemical order in the form of ionic complexes in the liquid Li–K–Pb system.