Ivanovski, V.N.; Cekic, B.; Umicevic, A.; Barudzija, T.; Schumacher, G.; Madarevic, I.; Koteski, V.: Site preference of Hf dopant in Ni3Al alloys: A perturbed angular correlation study. Journal of Alloys and Compounds 622 (2015), p. 541-544
10.1016/j.jallcom.2014.10.132

Abstract:
Perturbed angular correlation measurements of the hyperfine interactions of the 181Ta probe in the polycrystalline intermetallic Ni3Al doped with 0.5 and 5 at.% Hf were performed in the temperature range 78–1230 K. The observed local hyperfine fields at the 181Hf/181Ta probe showed that Hf atoms are substituting on Al sites in the L12 structure of Ni3Al. The two minor electric quadrupole interactions that were found for each Ni3Al alloy are discussed taking into account the L12 cubic structure and its two tetragonal distortions: D022 and L60. The presence of two tetragonal transformations of the parent cubic L12 lattice in 0.5 at.% Hf and 5 at.% Hf doped Ni3Al was revealed by X-ray diffraction. The ab initio calculations, performed with the projector augmented wave method correctly reproduce the experimental results and enable discussion on the structural and electronic properties of the polycrystalline alloys. The experimental and theoretical investigations showed that hafnium additions prefer aluminum sites in Ni3Al.