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

Abstract

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, V_obs = 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 (µ_eff) and Weiss temperature (Θ_pm) of 3.55 μ_B and − 4.5 K, respectively. While the observed µ_eff is very close to the theoretical value of 3.58 µ_B 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 (T_N) 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^− 1 m^− 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.

Graphical abstract