Neutron diffraction and observation of superconductivity for tungsten borides, WB and W_2B_4

摘要

Tungsten borides are known to be very hard and metallic materials. Tungsten monoboride, WB, becomes superconducting at T_c = 4.3 K in the tetragonal modification and T_c = 2.8 K in the orthorhombic modification. The structures of the two WB modifications were revised based on X-ray and neutron powder diffraction. W_2B_4, formerly known as W2B5, also shows a superconducting transition at 5.4 K, which is suppressed for small grain samples.