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Page 2 of 7 Sun et al. Microstructures 2023;3:2023028 https://dx.doi.org/10.20517/microstructures.2023.03

significant attention and development over the past three decades. The NTE is an important requirement
for the development of zero thermal expansion (ZTE) materials, which exhibit no dimensional changes
-1
-6
when subjected to heating. Materials with a coefficient of thermal expansion below 2 × 10 K are defined as
low thermal expansion (LTE) materials and find applications in various engineering environments, such as
electronic devices, optical instruments, and spacecraft. An example is Invar alloy Fe Ni , which has been
0.35
0.65
[1]
extensively used since its discovery in 1897 . Over time, other LTE alloys such as Fe-Co-Cr stainless steel
Invar alloys and other alloy compositions have emerged . In comparison with oxides , fluorides , and
[3]
[2]
[4]
[6]
cyanides , LTE alloys offer additional properties such as optical properties , excellent electrical, thermal
[5]
transport properties, and mechanical properties . Examples of such alloys include (Zr, Nb)Fe 2 [10,11] ,
[7-9]
(Sc, Ti)Fe , MnCoGe [13,14] , La(Fe, Si, Al) 13 [15,16] , RECo (RE = rare earth) [17,18] , REFe B , and RE Fe 17 [20,21] . The
[12]
[19]
2
2
14
2
metallic ZTE is known to be correlated with the magneto-volume effect (MVE), which refer to volume
changes induced by spontaneous magnetic ordering [16,22] .
Cubic Laves phase RECo has been studied intensively due to its relatively simple crystal and magnetic
2
structures. It belongs to a class of materials known for their magnetostrictive and magnetocaloric
[23]
properties . The compound is composed of two magnetic sublattices: one involving the local magnetic
moment of REs, and the other comprising the Co sublattice, which exhibits long-range magnetic ordering
induced by the molecular field of RE atoms [24,25] . In previous literature, samples TbCo Mn (y = 0, 0.1, 0.2,
2
y
and 0.3) were found to exhibit a rhombohedral structure (space group: R-3m) below the Curie temperature
(T ) and undergo a transition to a cubic structure (space group: Fd-3m) above T C [26] . TbCo Mn were
C
y
2
reported for the ZTE temperature window of about 40 K . Intriguingly, the introduction of the element Er
[23]
in compound TbCo Mn gives the Laves phase of Tb Er Co Mn , and their ZTE temperature windows can
y
2
y
1-x
x
2
be wider with increasing Er content. In the (RE RE' )(Co M ) compounds, the substitution of the RE'
x
1-y
y 2
1-x
atoms for the RE atoms occurs only in the 16d atomic site, while the substitution of the M atoms for Co
atoms takes place in the 8a site . This differs from the (RE RE' )Co Mn compounds, where the Mn atoms
[24]
1-x
x
2
y
can replace the 8a and 16d sites in the cubic structure with equal probability . This unusual modulation of
[27]
multiple sites in (RE RE' )Co Mn compounds significantly increases the T of the corresponding Mn-free
1-x
x
2
C
y
compounds. In this study, new intermetallic compounds Tb Er Co Mn (x = 0, 0.1, 0.2, 0.4, and 0.5, y = 0
y
2
x
1-x
and 0.1), with a MgCu type cubic structure, are introduced. These compounds can be modulated by
2
changing their components to achieve near ZTE.
MATERIALS AND METHODS
All the Laves-phase samples of Tb Er Co Mn (x = 0, 0.1, 0.2, 0.4, and 0.5, y = 0 and 0.1) were prepared by
x
1-x
y
2
arc melting under high-purity argon environment using raw materials with a purity of more than 99.9%,
which were weighed at the designed ratio of raw materials. To ensure homogeneity, the samples were
turned over and melted more than three times. At the end of the arc melting, the ingots are wrapped with
molybdenum foil and annealed in a vacuum-sealed quartz tube at 1,173 K for one week. The purity of the
samples was verified by a laboratory X-ray diffractometer (XRD, PANalytical X’Pert PRO) with Cu Kα
radiation. The scanning electron microscopy (SEM) imaging and X-ray energy dispersive spectroscopy
(EDS) elemental analysis were performed using a scanning electron microscope system (1,720, EPMA,
Shimadzu). All linear thermal expansion curves (ΔL/L ) were measured at a thermodilatometer (NETZSCH
0
DIL402) with a heating rate of 5 K/min. The magnetic properties were measured by a Physical Property
Measurement System (PPMS, Quantum Design company). Temperature dependence of the synchrotron
X-ray diffraction (SXRD) of the sample was collected at beamline of 11-BM-B (λ = 0.459073 Å) in the
Argonne National Laboratory (USA). All diffraction data were analyzed by the FULLPROF software.