Lattice location of B atoms in Ni_0.75Al_0.15Ti_0.10 intermetallic compounds as observed by the channeling method

The lattice location of B atoms doped in Ll₂-type Ni_0.75Al_0.15Ti_0.10 intermetallic compounds was investigated by the ion channeling method with a 720 keV proton beam. Backscattered protons, α-particles generated by the ¹¹B(p, α)⁸Be nuclear reaction and proton-induced X-rays were measured under channeling conditions. The channeling angular profiles for the α-particle yields exhibited a dip for the 〈100〉 and 〈111〉 channels, while a central peak for the 〈110〉 channel was observed, indicating octahedral (O) site occupancy of B atoms. There are two types of O-sites in a Ni₂Al-type compound: body-centered positions surrounded by six Ni atoms (site I), and edge-centered positions surrounded by four Ni atoms and two Al atoms (site II). For the 〈111〉 channel, the half-width of the channeling dip for the a yields agreed well to that for the Al K_α X-rays rather than that for the Ni K_α X-rays. Hence, it is concluded that most of the B atoms occupy O-sites of type-I (site-I).