Труды КНЦ вып.9 (ХИМИЯ И МАТЕРИАЛОВЕДЕНИЕ вып. 1/2018(9) часть 1)

Volume properties Some more information about the system behaviour and properties can be deduced from vo1ume properties. These properties are ca 1 cu 1 ated from experimenta 1 density data. Mo1ar vo1ume dependence on composition in binary systems is usua11y monotonic, but occasiona11y the presence of 1oca1 minimum can occur. This is the case for a11 investigated systems in this work. Mo1ar vo1ume of (LiF — CaF 2 )eut. — LnF 3 (Ln = La, Sm, Gd, and Nd) initia11y decreases with sma11 addition of LnF 3 up to 1 mo1 %. With further addition of LnF 3 the mo1ar vo1ume increses. A ca. x(LaF 3 ) = 0.04 the va1ue of the mo1ar vo1ume is comparab 1 e with that of the pure so 1 vent. With further SmF 3 addition (up to 50 mo1 %) mo1ar vo1ume increases up to ca 50 % higher va1ue in comparison to the initia 1 mo 1 ar vo 1 ume. With further addition of GdF 3 to (LiF — CaF 2 )eut mo1ar vo1ume increases 1ike in samarium ana1ogous system, however, the va1ues of mo1ar vo1ume decreases with temperature at particu1ar concentrations. This is significant1y different behaviour from the previous system. Reason for these observations is unknown and might arise from the structura 1 properties of gado 1 inium sa 1 t. Ana1ogous behaviour of vo1ume properties was observed for (LiF — CaF 2 )eut. — NdF 3 . These are, however, more c 1 ose to samarium system (without anoma 1 ous behaviour of mo 1 ar vo 1 ume) 1 ike in gado 1 inium system (i. e. va 1 ues of mo1ar vo1ume decreases with temperature at certain concentration). Mo1ar vo1ume shows 1oca1 minimum at 1ow NdF 3 concentrations, 1ike in Sm and Gd systems. When comparing va1ues of a11 three systems mo1ar vo1ume of Nd system at e.g. 15 mo1 % at 1123 К is 1owest in the series Nd < Sm < Gd what obeys the e1ements position in the periodic tab1e (but does not obey the sequence of mo1ar vo1umes of tri-f1uorides in so1id state that is Gd < Nd < Sm). More information about the vo1ume properties cou1d be founf in [23, 25]. Conclusions Temperatures of primary crysta11isation of the systems (LiF — CaF 2 )eut. — LnF 3 (Ln = Sm, Gd, and Nd) were measured in order to provide, at 1east, scheme of phase diagrams. Based on XRD patterns of so1idified samp1es it can be expected that some new phases are formed in a11 investigated systems. The number of these phases, however, cannot be predicted. In spite of the effort, severa1 procedures to obtain suitab1e sing1e crysta1s for their structura1 characterisation have fai 1 ed. Vo1ume properties ana1ysis revea1ed unusua1 behaviour of investigated systems, in some aspect even anoma1ous. Sma11 additions of LnF 3 up to 1mo1 % to (LiF—CaF 2 )eut. resu1t in decrease of mo1ar vo1ume. This has consequence to the partia1 mo1ar vo1umes of LnF 3 thus having very sma11 even negative va1ues at higher temperatures. Such a re1ative1y 1arge vo 1 ume contraction, when expressed through the compressibi 1 ity parameter, may reach va 1 ues that are bigger (in abso 1 ute va 1 ue) that mo 1 ar vo 1 ume of pure component. Samarium and neodymium systems show simi1ar properties in phase ana1ysis, as we11 as in vo1ume properties whi1e gado1inium system shows different behaviour. The reason for this macroscopic behaviour cou1d arise from the structura1 and e1ectronic properties of the centra1 atoms. The main difference between the studied three systems is that Nd3+and Sm3+have simi1ar e1ectronic properties in the sense of on1y partia11y occupied f orbita1s, whi1e Gd +3 has f orbita1s fu11y ha1f fi11ed. These different microscopic properties might resu1t a1so to the different macroscopic ones. In order to prove this hypothesis more extended experiments are required inc 1 uding a 1 so other 1 anthanides. Acknowledgement This work was supported by the Science and Techno1ogy Assistance Agency under contract No. APVV-0460-10 and by the S1ovak Grant Agency VEGA 2/0116/14. This publication is the result of the project implementation: “Applied research of technology of thermal plasma processes”, ITMS code 26240220070, supported by the Research & Deve1opment 0perationa1 Programme funded by the ERDF. References 1. Thermodynamic investigation of the (LiF + NaF + CaF 2 + LaF 3 ) system / M. Bei1mannet et a1. // J. Chem. Thermodyn. 2011. Vo1. 43. P. 1515-1524. 2. Physica1 properties of 1iquid NaF - LiF - LaF 3 and NaF - LiF - NdF 3 eutectic a11oys / L. Bu1avin et a1. // J. Nuc1. Mater. 2013. Vo1. 433. P. 329-333. 3. Benes O., van der Meer J. P. M., Konings R. J. M. 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