Syntheses of AlLB14(L=Li or Na) crystals using alkali fluorides and its properties

Abstract

Syntheses of AlLB14 (L=Li or Na or K) crystals were grown using LiF or NaF or KF and crystalline boron powders as the starting materials using high-temperature Al melt at soaking temperature 1573~1773 K for soaking time 5 h under an Ar atmosphere. A new compound AlNaB14 and AlLiB14 crystals were obtained from LiF or NaF and B powders, and the atomic ratios (n=B/L=2.0~4.0) of starting materials. AlKB14 crystal was not obtained from KF and B powders as starting materials. The micro-Vickers hardness of AlLB14 crystals is 24(±1) GPa for AlLiB14 and 25(±1) GPa for AlNaB14. The oxidation initiation temperature of AlLiB14 was about 815 K, and the peak due to the exothermic reaction was about 960 K for AlLiB14 and about 990 K for AlNaB14. The final oxidation products were Li2B2O4, Al4B2O9, B2O3 and amorphous phases. The values for the electrical resistivity of the AlLB14 compound were 2.4~157 Ω·cm