I. INTRODUCTION
Many AB5 intermetallic compounds, a metal hydride with hexagonal CaCu5 type structure, can react reversibly with hydrogen at moderate pressure and temperature and exhibit excellent hydrogen storage properties. These compounds are extensively investigated and pseudobinary compounds obtained by partial replacement of the constituents in LaNi5 have also been examined in order to improve hydriding properties for specific applications. It has been found that these substitutions induce a large change in both the stability and the capacity of the related hydrides (Percheron-Guegan et al., Reference Percheron-Guegan, Lartigue and Achard1985). So far, powder diffraction data of the quaternary compound PrAlFeNi3 have not included in the PDF (ICDD, Reference Kabekkodu2011). Therefore, in this paper, we present high-quality experimental powder XRD data for PrAlFeNi3.
II. EXPERIMENTAL
A. Synthesis
The sample of PrAlFeNi3 with a total mass of 2 g was prepared by arc melting using a non-consumable tungsten electrode and a water-cooled copper tray under argon atmosphere. Praseodymium (purity of 99.9%), aluminum (purity of 99.8%), iron (purity of 99.9%), and germanium (purity of 99.9%) were used as the starting materials. Titanium was used as an oxygen getter during the melting process. The sample was remelted three times in order to ensure the complete fusion and homogeneity. Weight losses were less than 1 wt%. After melting, the sample was enclosed in an evacuated quartz tube and annealed at 1073 K for 720 h, then cooled down at a rate of 10 K h−1 to room temperature. The sample was ground in an agate mortars and pestled to particle sizes of no larger than 45 μm.
B. Data collection
Powder X-ray diffraction (XRD) patterns of PrAlFeNi3 compound were collected at room temperature using a Rigaku Smart Lab 2006 powder diffractometer equipped with a CuKα radiation and a diffracted-beam graphite monochromator. The diffractometer was operated at 40 kV and 180 mA, the 2θ scan range was from 10 to 100° with a step size of 0.02° and a count time of 3 s per step. Two sets of XRD data were collected, one with SRM 640 Si added as an internal standard to correct for possible systematical errors in the observed peak positions and the other without SRM 640 Si. The XRD pattern recorded from the specimen added with Si internal standard was used for indexing and for determining space group and unit-cell information, while the XRD pattern without Si internal standard was used for determining diffraction intensities. The 2θ obs values of the peaks were determined by the Savitzky–Golay second derivative using JADE 6.0 (Materials Data Inc., 2002) XRD Pattern Processing software of Materials Data, Inc. after smoothing the patterns, fitting and removing the background, and stripping the CuKα 2 peaks. Values of unit-cell parameters were then obtained by the least-squares method using JADE 6.0.
III. RESULTS
The experimental XRD pattern of compound PrAlFeNi3 is shown in Figure 1. All lines were successfully indexed using the Jade6.0 program in hexagonal structure. By comparing powder XRD data of PrAlFeNi3 with those of LaMn1.13Ni3.87 (PDF2, 00-033-0707#), it was found that PrAlFeNi3 and LaMn1.13Ni3.87 (Achard et al., Reference Achard, Givord, Percheron-Guegan, Soubeyroux and Tasset1979) have the same structure type P6/mmm (No. 191). Using the corrected diffraction data of PrAlFeNi3, the accurate lattice parameters were obtained: a = 5.1132(2) Å, c = 4.0737(1) Å, V = 92.19 Å3, Z = 1, and ρ x = 7.20 g cm−3. The figure of merit for indexing F N (Smith and Snyder, Reference Smith and Snyder1979) is 173.61 (0.0054, 32) and the value of RIR (RIR = 0.77) was obtained from the value of the ratio of the strongest line in the pattern to the strongest line of corundum in a 50–50 wt percent mixture of the two compounds. The observed and the calculated X-ray powder diffraction data (Prince, Reference Prince2004) for PrAlFeNi3 are listed in Table I.
aΔ2θ=2θ cal − 2θ obs.
ACKNOWLEDGEMENT
This work was supported by the Scientific Foundation of Guangxi High Education (2013ZD070).
SUPPLEMENTARY DATA
The supplementary material for this article can be found at http://www.journals.cambridge.org/PDJ