Crystalline phases in Zr9Ni11 and Hf9Ni11 intermetallics; Investigations by perturbed angular correlation spectroscopy and ab initio calculations

TL;DR

This study investigates the crystalline phases of Zr9Ni11 and Hf9Ni11 intermetallics using PAC spectroscopy, XRD, TEM/SAED, and ab initio calculations, revealing phase compositions and temperature-dependent decompositions.

Contribution

It combines experimental PAC, XRD, TEM data with DFT calculations to identify and analyze phase components and their temperature evolution in Zr9Ni11 and Hf9Ni11 intermetallics.

Findings

Zr9Ni11 mainly present at room temperature with partial decomposition at high temperatures.

Hf9Ni11 predominantly contains HfNi phase with no phase change at higher temperatures.

Phase components from PAC agree with XRD and TEM/SAED results.

Abstract

Crystalline phases formed in stoichiometric Zr$_9$Ni$_{11}$ and Hf$_9$Ni$_{11}$ have been studied by perturbed angular correlation (PAC) spectroscopy, XRD and TEM/SAED measurements. In Zr$_9$Ni$_{11}$, the phases Zr$_9$Ni$_{11}$ ($\sim$89\%) and Zr$_8$Ni$_{21}$ ($\sim$11\%) have been found at room temperature from PAC measurements. At 773 K, Zr$_9$Ni$_{11}$ partially decomposes to Zr$_7$Ni$_{10}$ and at 973 K, it is completely decomposed to ZrNi and Zr$_7$Ni$_{10}$. In Hf$_9$Ni$_{11}$, a predominant phase ($\sim$81\%) due to HfNi is found at room temperature while the phase Hf$_9$Ni$_{11}$ is produced as a minor phase ($\sim$19\%). No compositional phase change at higher temperature is found in Hf$_9$Ni$_{11}$. Phase components found from XRD and TEM/SAED measurements are similar to those observed from PAC measurements. Electric field gradients in Zr$_9$Ni$_{11}$ and Hf$_9$Ni$_{11}$ have been calculated by density functional theory (DFT) using all electron full potential (linearized) augmented plane wave plus local orbitals [FP-(L)APW+lo] method in order to assign the phase components.