Thermopower of CexR1-xB6 (R=La, Pr and Nd)

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The thermopower, S, of CexR1-xB6 (R=La, Pr, Nd) was investigated. S with a positive sign shows a typical behavior observed in the Ce Kondo system, an increase with decreasing temperature at high temperatures and a maximum at low temperatures. The S values of all the systems at high temperatures are roughly linearly dependent on the Ce concentration, indicating the conservation of the single-impurity character of the Kondo effect in a wide x range. However, the maximum value of S, Sₘax, and the temperature, Tₘax, at which Sₘax is observed exhibit different x dependences between CexLa1-xB6 and CexR1-xB6 (R=Pr, Nd). In CexLa1-xB6, Tₘax, which is 8 K in CeB6, decreases with decreasing x and converges to 1 K in a very dilute alloy and Sₘax shows an increase below x 0.1 after decreasing with decreasing x. In CexR1-xB6 (R=Pr, Nd), Tₘax shows a weak x dependence but Sₘax shows a roughly linear decrease in x. These results are discussed from the standpoint of the chemical pressure effect and the Ce-Ce interaction. S in the long-range ordered phase shows very different behavior between CexPr1-xB6 and CexNd1-xB6.