Synthesis, crystal structure and physical properties of the TbCo4.5SixLi0.5-x solid solution

I Stetskiv,V Kordan,V Pavlyuk,I Tarasiuk

doi:10.15330/pcss.22.3.577-584

I Stetskiv, V Kordan + Show 2 more

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https://doi.org/10.15330/pcss.22.3.577-584

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Abstract

Alloys from the region of existence of the solid solution TbCo4.5SixLi0.5-x were synthesized by arc melting. Quantitative and qualitative composition of alloys and powders of electrode materials was determined by scanning electron microscopy and energy-dispersive X-ray spectroscopy. The Tb/Co/Si ratio in the samples was confirmed by X-ray fluorescence spectroscopy. The change in cell parameters within the solid solution existence was established by the results of X-ray powder diffraction (TbCo4.5SixLi0.5-x, x = 0.1–0.4: a = 4.9518(5) – 4.9324(3), c = 3.9727(4) – 3.9746(3) Å). The crystal structure of the solid solution was determined by the Rietveld method (CaCu5 structure type, space group P6/mmm). Cobalt atoms are partially replaced by silicon and lithium only in 2c position. The ability of alloys to reversibly absorb hydrogen was studied by the method of electrochemical hydrogenation. Under experimental conditions the amount of deintercalated hydrogen was about 0.19 H/f.u. The change in cell parameters after hydrogenation (volume increases from 83.74(1) to 85.54(6) Å3) and the stability of the electrode in the electrolyte solution was further confirmed by X-ray phase analysis. Measurements of the electrical resistivity of the samples indicated a decrease of resistivity value with a slight increase in the amount of alkali metal in samples.

Highlights

The implementation of renewable energy sources is one of the most important tasks of modern science and industry
Creating safe and efficient systems for its storage and transportation is a difficult task, as the use of compressed gaseous or molecular hydrogen carries a lot of risks
To investigate the solubility of elements that improve hydrogenation process (Li and Si) in the TbCo5 binary intermetallic compound, we prepared a series of samples in quaternary system Tb–Co–Si–Li

Summary

Introduction

The implementation of renewable energy sources is one of the most important tasks of modern science and industry. The accumulation of hydrogen in the form of hydrides of metals and intermetallic compounds is a possible solution to the above problems. The study of such chemical sources of electric current began after the revealing of the ability of materials such as LaNi5, SmCo5, FeTi, ZrNi2, Mg-based alloys [1] to absorb and desorb hydrogen. Use of Al, Mg, Mn, Ni, and Co as alloying components results into the improvement of corrosion stability, increasing of life-time and capacity of electrode materials [4 - 8]. Improvement of the hydrogen sorption ability, specific capacity and corrosion potential was observed after the doping of metallic Mg-based electrode with Li and Al [9, 10]

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