Syntheses and some properties of solid solution Yb(Al,T)B4 (T = Mo or W) compounds

RAlB4 (R = rare earth element) has attracted increasing attention due to recent reports on its properties in magnetic, thermoelectric and superconducting materials. The authors developed and we investigated the formation of the solid solution Yb(Al0.995T0.005)B4 (T = Cr, Mn or Fe) compounds in which the Al position of YbAlB4 is substituted with T atoms using the Al flux method. In this study, crystals of the boride Yb(Al0.995T0.005)B4 (T = Mo or W) were grown by using Al flux mixed with T metal at 1773 K for 5h. Yb(Al0.995W0.005)B4 was obtained as the single phase, however, in the case of Yb(Al0.995Mo0.005)B4, a small amount of AlMoB crystals was contained. The crystals were measured using a micro-Vickers hardness tester, and the oxidation resistance was examined in air using DTA-TG apparatus. Comparing the lattice constants and chemical composition of YbAlB4 and Yb(Al0.995T0.005)B4, it were understood that the lattice constant of Yb(Al,T)B4 were larger than that of YbAlB4 crystals. Yb(Al,T)B4 were grown as a solid solution contained about 40 % of each T metal. The hardness values were 11.0(±0.7) GPa for Yb(Al0.995Mo0.005)B4 and 15.7(±1.9) GPa for Yb(Al0.995W0.005)B4. The oxidation of Yb(Al,T)B4 starts in the range of 971–987 K. The oxidation onset temperature during the heating of Yb(Al,T)B4 is about 100 K higher than YbAlB4. We investigated the formation of the solid solution Yb(Al0.995T0.005)B4 (T = Fe, Cr, Mo, Mn, W) compounds in which the Al position of YbAlB4 is substituted with T atoms using the Al flux method. ✓ From the result of XRD patterns, Yb(Al0.995T0.005)B4 (T = Fe, Cr, Mn, W) was obtained as a single phase, however, in the case of Yb(Al0.995Mo0.005)B4, a small amount of MoAlB was contained. ✓ Comparing the lattice constants of YbAlB4 and Yb(Al,T)B4, the lattice constants of Yb(Al,T)B4 (T = Fe, Cr, Mo, Mn, W) tends to be smaller when Cr, Fe or Mn metals were contained, and tends to be larger when Mo or W metals were contained. [Display omitted] •RAlB4 has attracted increasing attention due to recent reports on its properties in magnetic, thermoelectric and superconducting materials.•Crystals of the boride Yb(Al0.995T0.005)B4 (T = Mo or W) compounds were grown by using Al flux mixed with T metal.•We measured the lattice constants and chemical composition, micro-Vickers hardness and the oxidation onset temperature of Yb(Al0.995T0.005)B4 (T = Mo or W) compounds.