B. Wodniecka

The hafnium aluminides HfAl3 and Hf2Al3 studied by perturbed angular correlations with 181Ta and 111Cd probes

Abstract The electric quadrupole hyperfine interactions for 181 Hf/ 181 Ta and 111 In/ 111 Cd probes in the polycrystalline hafnium aluminides HfAl 3 and Hf 2 Al 3 were measured in the temperature range 30–1100 K. On the basis of the similarities of the numbers, sizes and asymmetries of electric field gradients, lattice site allocations were made. In all matrices, 181 Hf/ 181 Ta was found to substitute into the Hf site. The 111 In/ 111 Cd impurities were also assigned to the Hf lattice site in the low-temperature phase of HfAl 3 , which has D0 23 structure, but appear to substitute into the two non-equivalent Al sites in the Hf 2 Al 3 phase, which has Fdd2 crystallographic structure.

Hf and Zr aluminides with Bf-type structure studied by PAC with 181Ta and 111Cd probes

The hyperfine quadrupole interaction parameters and their temperature dependences for 181Hf/181Ta and for 111In/111Cd probes in the polycrystalline HfAl and ZrAl isostructural compounds were determined. Strong preference of 111In solute for the Zr2Al3 phase occurring as a contamination fraction in ZrAl sample was observed.

The HfAl2 and ZrAl2 Laves phases studied by 181Ta and 111Cd perturbed angular correlation spectroscopy

Abstract Using perturbed angular correlation (PAC) spectroscopy and 181 Hf/ 181 Ta and 111 In/ 111 Cd radioactive probes, the electric field gradients (EFGs) in the ZrAl 2 and HfAl 2 Laves phases were measured in the temperature range 20–1100 K. In both matrices, 181 Hf was found to substitute at the unique Hf/Zr site. In the ZrAl 2 compound, the 111 In probes were assigned to the two Al sites. The relative fractions of the corresponding EFGs indicate a strong preference of these impurities in favor of the 2( a ) Al site over the 6( h ) Al site. In the HfAl 2 compound, the 111 In impurities substitute for Hf up to 370 K and reach the Al sites only above 420 K. In both compounds and for both radioactive probes, the temperature dependence of the quadrupole interaction frequencies was measured. It is interesting to note that, for 181 Ta in both compounds, they increase with temperature.

Hyperfine interaction of 111Cd in Fe–Sn compounds

The hyperfine interaction of 111Cd in ferromagnetic Fe3Sn compound was investigated by TDPAC in the paramagnetic region and below the Curie temperature. The results are compared with hyperfine magnetic fields and EFGs on 111Cd and 119Sn in other stoichiometric Fe–Sn phases.

The Zr2Al and Zr3Al compounds studied by PAC with 181Ta and 111Cd probes

Abstract The perturbed angular correlation technique was applied to study the electric field gradients of 111 In/ 111 Cd and 181 Hf/ 181 Ta radioactive probe atoms in the compounds Zr 2 Al and Zr 3 Al. In both matrices 181 Hf/ 181 Ta was found to substitute into the Zr sites. The 111 In/ 111 Cd probes were assigned to the unique Al site in the Zr 2 Al compound, while in the Zr 3 Al compound they were distributed between the unique Zr and Al positions of this lattice, with a clear preference for the Al site. The temperature dependences of the various quadrupole frequencies were measured in the temperature range from 20 to 1100 K.

Perturbed angular correlation measurements at 181Ta in Hf2Pd and Zr2Pd tetragonal MoSi2-type phases

Abstract The electric quadrupole interaction at 181 Ta in Hf 2 Pd and Zr 2 Pd compounds was studied by the perturbed angular correlation method in a broad temperature range. The powder X-ray analysis verified a single-phase C11 b structure of the samples. The least-squares fits of the perturbation factor to the experimental spectra measured for Hf 2 Pd and Zr 2 Pd compounds yielded an electric interaction with a well-defined single quadrupole frequency ( v Q = 305(2) MHz for Hf 2 Pd and 291(4) MHz for Zr 2 Pd) and asymmetry parameter η = 0, reflecting the existence of one axially symmetric probe site. A decrease in the quadrupole interaction frequency with an increase of temperature is very rapid for both Hf 2 Pd and Zr 2 Pd compounds.

Electric quadrupole interaction at 181Ta probes in hexagonal TiNi3-type compounds

Abstract The perturbed angular correlation technique was applied to study the electric field gradient (EFG) in TiNi 3 -type compounds. HfPd 3 , Zr 0.98 Hf 0.02 Pd 3 and Ti 0.98 Hf 0.02 Pd 3 samples were neutron irradiated in order to produce 181 Ta probes. The perturbed angular correlation measurements performed in the temperature range 45 K–1100 K demonstrated the existence of two axially symmetric EFGs in each of the investigated compounds related to the 2(a) and 2(c) probe sites in the D0 24 structure. The temperature dependence of the quadrupole frequencies exhibits different slope parameters for each of the observed frequencies.

Phase transition in Ni.30In.70 alloy studied with PAC method

Abstract Nickel–indium intermetallic compounds of different stoichiometries were studied by means of the perturbed angular correlation (PAC) spectroscopy. The temperature dependence of the hyperfine interaction parameters for 111 Cd probes in the crystal lattices of Ni 3 In 7 and Ni 2 In 3 was measured. A T 3/2 character of the electric field gradient temperature dependence was found. The temperature of the peritectic reaction in the Ni .30 In .70 sample was determined.

Co–Sn intermetallic phases and their formation at the Co/Sn interface studied with perturbed angular correlation (PAC) method

Abstract Cobalt–tin intermetallic compounds of different stoichiometries were studied by means of the perturbed angular correlation (PAC) technique. The hyperfine interaction parameters for 111Cd probes in the crystal lattices of CoSn2 and Co3Sn2 were determined. A T3/2 temperature dependence of the electric field gradient (EFG) in CoSn2 compound was found. Due to the thermal interdiffusion in a bilayer Co/Sn sample the formation of the stoichiometric CoSn phase was observed.