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• 作者：B. Chevalier ; B. Heying ; U. Ch. Rodewald ; C. Peter Sebastian ; E. Bauer ; R. Pö ; ttgen
• 刊名：Chemistry of Materials
• 出版年：2007
• 出版时间：June 12, 2007
• 年：2007
• 卷：19
• 期：12
• 页码：3052 - 3060
• 全文大小：225K
• 年卷期：v.19,no.12(June 12, 2007)
• ISSN：1520-5002

文摘

The ternary gallides Ce(Rh_1-xIr_x)Ga with x = 0, 0.54, and 1 were synthesized from the elements byarc-melting. The structures of these intermediate valence compounds were investigated on the basis ofpowder and single-crystal X-ray diffractometer data: TiNiSi type, Pnma, a = 688.2(2), b = 439.6(1),and c = 788.9(1) pm, wR2 = 0.0493, 563 F² values, and 20 variable parameters for CeRhGa; a =685.5(1), b = 436.0(1), and c = 782.7(1) pm, wR2 = 0.0685, 563 F² values, and 21 variable parametersfor Ce(Rh_0.46Ir_0.54)Ga; and a = 690.1(1), b = 436.6(1) and c = 785.2(2) pm, wR2 = 0.0810, 562 F²values, and 20 variable parameters for CeIrGa. The rhodium (or iridium) and gallium atoms build upthree-dimensional [RhGa] and [IrGa] networks with Rh-Ga (or Ir-Ga) distances ranging from 265 to267 pm (or from 265 to 269 pm). The cerium atoms fill distorted hexagonal channels within these networkswith one short Ce-Rh (or Ce-Ir) contact (281 pm in CeRhGa, 283 pm in Ce(Rh_0.46Ir_0.54)Ga, and 287pm in CeIrGa). Hydrogenation leads to the formation of the hydrides Ce(Rh_1-xIr_x)GaH_1.8 in going witha switch in structure type: ZrBeSi type, P6₃/mmc, a = 437.3(1) and c = 839.2(1) pm for CeRhGaH_1.8,a = 440.1(1) and c = 829.1(1) pm for Ce(Rh_0.46Ir_0.54)GaH_1.8, and a = 441.8(1) and c = 823.3(1) pm forCeIrGaH_1.8. Susceptibility and specific heat measurements on the hydrides reveal stable trivalent ceriumand antiferromagnetic ordering at low temperatures; the Néel temperature decreases with the rhodiumcontent. Fitting of the susceptibility data of the hydrides considering the crystal field splitting and molecularfield effects clearly revealed the doublet r.gif">₉ =rbar.gif"> ±³/₂ as the ground state. Electrical resistivity data andthermoelectric power measurements show the characteristics of Kondo systems.