The new PrNi6Si6 intermetallic: from crystal structure to thermal and electrical transport properties across a wide temperature range (2–900 K)

In the present study, the new ternary rare-earth intermetallic compound PrNi6Si6 has been investigated. This work completes the study of the RNi6Si6 series (R= rare earth). While the RNi6Si6 compounds for R = La and Ce adopt the CeNi6Si6-type (tP52, P4/nbm, No. 125), surprisingly PrNi6Si6 crystallizes in the YNi6Si6 prototype (tP52, P4b2, No. 117) as do all the heavier lanthanides (but Lu). The YNi6Si6-type and its homolog CeNi6Si6, are two tetragonal ordered derivative of the cubic NaZn13-type structure. Lattice parameters for PrNi6Si6 are a = 7.7846(1) Å, c = 11.2144(1) Å, with a unit-cell volume, Vobs = 679.585(5) Å3. The temperature dependence of the inverse magnetic susceptibility χ1 (T) follows the Curie-Weiss law, with calculated values of the effective magnetic moment (µeff) and the Weiss temperature (pm) of 3.55 B and 4.5 K, respectively. While the observed µeff is very close to the theoretical value of 3.58 µB for the free Pr3+ ions, a negative value of the Weiss temperature suggests antiferromagnetic interactions in PrNi6Si6. Magnetization measurements confirm that PrNi₆Si₆ orders antiferromagnetically (AFM) below a Néel temperature (TN) of 9 K. The Ni atoms contribute negligibly to the magnetic properties of this phase. The specific heat of PrNi₆Si₆ is approximately 0.42 J·K⁻¹·g⁻¹. Measurements of electric and thermal transport reveal that PrNi₆Si₆ exhibits metallic behavior across a wide temperature range of 2-900 K, accompanied by a relatively low thermal conductivity of around 6 W K⁻¹m⁻¹ at room temperature. Such properties, together with its high-temperature refractory behavior, make PrNi₆Si₆ worthy of consideration in technological applications where fairly good electrical conductivity should be accompanied by a limited thermal conductivity.