Thermal stability of the Cu–ZrTe2 intercalation compounds

Journal Pre-proof Thermal stability of the Cu–ZrTe2 intercalation compounds Alexey S. Shkvarin, Alexey A. Titov, Mikhail S. Postnikov, Jasper R. Plaisier, Lara Gigli, Mattia Gaboardi, Alexander N. Titov, Elena G. Shkvarina PII:

S0022-2860(19)31753-3

DOI:

https://doi.org/10.1016/j.molstruc.2019.127644

Reference:

MOLSTR 127644

To appear in:

Journal of Molecular Structure

Received Date: 26 October 2019 Revised Date:

19 December 2019

Accepted Date: 23 December 2019

Please cite this article as: A.S. Shkvarin, A.A. Titov, M.S. Postnikov, J.R. Plaisier, L. Gigli, M. Gaboardi, A.N. Titov, E.G. Shkvarina, Thermal stability of the Cu–ZrTe2 intercalation compounds, Journal of Molecular Structure (2020), doi: https://doi.org/10.1016/j.molstruc.2019.127644. This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version will undergo additional copyediting, typesetting and review before it is published in its final form, but we are providing this version to give early visibility of the article. Please note that, during the production process, errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain. © 2019 Published by Elsevier B.V.

Thermal stability of the Cu-ZrTe2 intercalation compounds. Alexey S. Shkvarin1*, Alexey A.Titov1, Mikhail S. Postnikov1,2, Jasper R. Plaisier3, Lara Gigli3, Mattia Gaboardi3, Alexander N. Titov1,2, Elena G. Shkvarina1 1

Institute of Metal Physics, Russian Academy of Sciences-Ural Division, 620990 Yekaterinburg, Russia 2 3

Ural Federal University, 620089 Yekaterinburg, Russia

Elettra Sincrotrone Trieste SCpA, Area Science Park, S.S. 14 km 163.5, 34012 Basovizza, Italy

*S.Kovalevskoy str. 18, 620990 Yekaterinburg, Russia, tel.: +7(343)378-35-49, [email protected]

Keywords Thermal stability, transition metal dichalcogenides, in-situ high-temperature XRPD, x-ray diffraction

Abstract An experimental study of the phase stability of the CuxZrTe2 compound (0
Introduction The M-TiX2 (M = Ag, Cu, Fe etc .; X = S, Se, Te) intercalation compounds have been widely studied in the past [1–6]; it has been shown that the type of phase diagrams of these systems is determined by the nature of the chemical bond of the intercalated metal within the host lattice [7,8]. The covalent component of the bond is provided by the hybridization of the valence states of the intercalated atom and the Ti3d or Xnp valence states of the host lattice atoms from the nearest environment of the intercalated atom. The band of these hybrid states is located near the Fermi level, so that the temperature affects the degree of filling of this band through the thermal blurring of the atomic configuration of the covalent complex, which leads to the change in the density of states near the Fermi level. A change in the density of states near the Fermi level can cause a shift of the Fermi level, stabilizing or, conversely, destabilizing the single-phase state. This is possibly due to the high polarizability of the host lattice. This effect is anticipated to be more significant in the ZrX2 intercalation compounds than in the TiX2 due to the higher polarizability of the Zr atoms in comparison with Ti. This feature is likely most pronounced in the ZrTe2, as the most polarizable lattice of this homologous series. Moreover, the zirconium dichalcogenides are characterized by a wider energy gap than the titanium dichalcogenides [9–11]. Therefore, we can assume that the influence of 1

the temperature dependence of width of the hybrid states band will be more significant in the intercalation compounds M-ZrX2 than in the already studied M-TiX2. Intercalation compounds based on titanium and zirconium dichalcogenides can be used as materials for electrochemical devices [12,13]; they are promising materials for producing monolayer field-effect transistors [14,15] and for the creation of the optoelectronic devices [16]. Intercalation provides an opportunity to change and optimize functional properties. In particular, the intercalation of copper, which in most cases exhibits donor properties, makes it possible to control the concentration of charge carriers and optimize the thermoelectric properties of these materials [17,18]. We have shown that intercalation of copper in ZrSe2 leads to the formation of a material with a direct energy gap [19], which makes this material promising for optoelectronics and photovoltaics. Recently, zirconium dichalcogenides have attracted attention due to the possibility of obtaining nanoribbons with a direct energy gap. This gap was predicted based on band calculations [20,21]. Nanoribbons can be are easily obtained by gas transport synthesis and they are good precursors for monolayer or few-layered objects for nanoelectronics. At the same time, experimental data on phase ratios in the intercalation compounds of zirconium dichalcogenides are poorly described in the available literature. This work aims to fill this gap. The Cu atoms can occupy crystallographic sites with different coordination by chalcogen [17,22] which leads to the possibility of the formation of different covalent complexes. Figure 1 shows the fragments of crystal structure, where the copper atom occupies an octahedral or tetrahedral site.

Figure 1. Fragment of the crystal structure of CuxZrTe2 with Cu atoms in octahedral (right panel) and tetrahedral (left panel) position in the interlayer space.

The phase diagram of the Cu-ZrTe2 system is expected to be the most complex and diverse among that of the intercalation compounds of transition metal dichalcogenides, which have been 2

studied recently. According to our structural studies for Cu0.5ZrTe2 [23], the Cu atoms can occupy sites in the ZrTe2 lattice, both octa- and tetrahedrally coordinated by tellurium. In these cases, we can expect the formation of various hybrid states of copper atoms with the nearest environment. This paper is devoted to studying the effect of copper coordination on the position of the equilibrium boundary of single-phase region in the range of compositions close to the already studied Cu0.5ZrTe2.

Experimental The CuxZrTe2 polycrystalline samples were synthesized in the range of 0 ≤ x ≤ 0.4 using previously prepared ZrTe2 and metallic copper. ZrTe2 was obtained from the starting elements: Zr (iodine purification, 99.95%) (VSMPO-AVISMA) and Te (after double distillation in a vacuum, ChDA, 99.99%). The appropriate amount of the starting elements was sintered at 1000 °C for 7 days in sealed quartz ampoules, evacuated to 10-5 Torr. After that the ampoules were opened, the samples were ground, pressed, and again annealed under the same conditions for a week for homogenization. The CuxZrTe2 samples were obtained by usual thermal intercalation procedure. The appropriate amount of granulated copper of high purity (OSCh) and previously prepared powder ZrTe2 were pressed in a pellet and annealed at 1000 °C in evacuated to 10-5 Torr quartz ampoules for a week. The resulting product was thoroughly ground in an agate mortar, pressed and annealed again under the same conditions for complete homogenization. The final product was macroscopically homogeneous. The structure and phase composition of the samples was studied at room temperature using X-ray powder diffraction (Shimadzu XRD 7000 Maxima diffractometer CCU Ural-M). The structure and phase composition of obtained samples were studied by the quenching method — polycrystalline samples of CuxZrTe2 (0 ≤ x ≤ 0.4) were annealed at a given temperature (250 °C, 400 °C, 600 °C, 750 °C, 900 °C, 1000° C, 1050 °C), quenched and studied using the X-ray diffraction. The sample was mantained at the temperature higher than 400 °C for a week and then for 2 weeks at 250 °C. The in situ time-resolved (temperature dependent) SR-XRPD experiments of Cu0.2ZrTe2 were performed at the MCX beamline of Elettra Sincrotrone Trieste (Italy) [24] in transmission mode, with a monochromatic wavelength of 0.827 Å (15 KeV) and 1x0.3 mm2 spot size. The polycrystalline sample was carefully packed into a quartz capillary with an inner diameter of 0.3 mm. The capillary, mounted on a standard goniometric head, and spun during data collection, was first evacuated and then filled with argon to create an inert atmosphere. The sample was heated from room temperature to 1000 o

C with a ramp rate of 5°C /min. using the gas blower .The diffraction patterns were collected using

the t scintillator detector available on the high resolution Huber diffractometer. Each pattern was collected in the 5-50 2Θ range with a step size of 0.01 degree and an exposure time of 1 second. The 3

equilibration time of a sample at a given temperature before a measurement varies from 5 minutes to 1 hour depending on the temperature. The wavelength was calibrated using Si as an external standard, while temperature calibration was achieved by measuring the thermal expansion of Si collected under the same experimental conditions. The profile parameters obtained for the refinement of the pattern of silicon were used in refinement of the patterns of the studied samples. The crystal structure of quenched polycrystalline CuxZrTe2 samples was studied using X-ray powder diffraction (XRD) on a Shimadzu XRD 7000 Maxima diffractometer (Cu Kα1 radiation, graphite monochromator, 2Θ = 5 - 90о). The crystal structure refinement was performed using GSAS (General Structure Analysis System) [25]. The starting model was as follows: space group P-3m1, atomic coordinates Zr (0 0 0), Te (1/3 2/3 z), z ≈ 0.254; two sites were available for the Cu atoms in the interlayer space Cu (0 0 1/2), and Cu (1/3 2/3 z), z ≈ 0.63. The background was approximated by the Chebyshev polynomial.

Results and discussion From the Fig.2 (left panel) and Table 1 and 2 it can be seen that the intercalation of the Cu atoms at 900 and 1000 oC leads to the appearance of the phases of constant composition (ZrTe2 and Cu0.5ZrTe2). The increase in the starting copper concentration leads to an increase in the weight fraction of the Cu0.5ZrTe2 (Table 1, 2). The formation of a two-phase region of the pristine phase and the intercalation compound with the minimum concentration of the intercalated atoms was also observed in similar systems such as, Ag-ZrSe2, Ag-TiTe2 and Ag-TiSe2 [26–29].

4

Figure 2. The weight fractions of the constituent phases in dependence of the quenching temperature (left panel) and insitu temperature (right panel).

Table 1. The refinement results for the intercalation phase in the annealed and quenched CuxZrTe2 (x= 0.2, 0.3). T, ˚C

Layered hexagonal phase a, Å

c, Å

Te (⅓ ⅔ z) Cu (0 0 ½) z

occupation

Cu (⅓ ⅔ z) z

occupation

Zr (⅓ ⅔ z) z

occupation

RF2, % wRp, %

Rp, %

χ2

Weight Fract., %

Cu0.2ZrTe2 250

3.9509(1) 6.6237(3) 0.2729(3)

-

0.463(4)

0.097(4)

0.51(1)

0.041(4)

6.97

12.40

9.47

2.261

64.6

400

3.9489(1) 6.6203(3) 0.2716(3)

0.01(1)

0.478(5)

0.11(1)

0.462(7)

0.055(3)

6.09

14.20

10.90

2.657

67.6

600

3.9497(1) 6.6227(3) 0.2753(3)

-

0.477(4)

0.127(5)

0.64(1)

0.028(5)

6.62

12.29

9.21

2.723

68.8

750

3.9501(1) 6.6267(3) 0.2715(3)

-

0.50(1)

0.147(7)

-

-

4.82

13.76

10.83

2.930

69.2

900

3.9504(2) 6.6205(3) 0.2705(3)

0.45(2)

0.63(1)

0.06(1)

0.58(1)

0.036(6)

1.29

11.09

8.42

2.443

38.3

5

1000

3.9544(2) 6.6259(2) 0.2706(3)

0.47(1)

-

-

-

-

1.60

8.81

6.54

1.781

45.2

-

0.42(1)

0.029(4)

0.51(1)

0.046(3)

4.69

12.22

9.53

2.411

57.6

Slowly 3.9481(1) 6.6203(3) 0.2711(3) cooled

Cu0.3ZrTe2 400

3.9498(1) 6.6203(3) 0.2709(3)

-

0.48(1)

0.131(6)

0.45(1)

0.059(4)

4.77

12.27

9.36

2.381

69.7

750

3.9529(1) 6.6300(4) 0.2717(4)

-

0.51(1)

0.147(6)

0.41(1)

0.039(4)

2.13

11.82

9.21

2.555

62.4

Table 2. The distribution of the phases in the Cu0.2ZrTe2 after annealing for a week at a corresponding temperature. Slowly

T, ˚C

250

400

600

750

900

1000

CuxZrTe2

64.6

67.6

68.8 %

69.2 %

38.3 %

45.2 %

57.6 %

ZrTe3

27.1(6)

22.4(2)

13.5(1) %

19.9(3) %

19.4(1) %

10.2(2) %

31.0(4) %

Cu1.4Te

3.4(2)

2.8(2)

1.9(2) %

-

-

-

6.8(3) %

Zr5Te4

2.4(2)

2.8(2)

8.3(3) %

4.6(2) %

-

-

1.5(1) %

Te

2.5(1)

2.9(1)

7.0(2) %

4.4(2) %

-

-

2.3(1) %

ZrSiO4

-

1.5(1)

0.5(1) %

1.9(1) %

-

-

-

ZTe2

-

-

-

-

42(1) %

44.6(5) %

-

ZrO2

-

-

-

-

-

-

0.9(1) %

cooled

A mixture of CuxZrTe2, ZrTe3 and binary copper telluride phases is observed in the temperature range 250-750 ˚C. At the same time, heating from 250 to 900 ˚C leads to the copper enrichment from Cu0.25ZrTe2 at 250 ˚C to Cu0.5ZrTe2 at 1000 ˚C in the intercalation phase, which is in equilibrium with ZrTe2. The temperature dependence of the copper concentration in the CuxZrTe2 demonstrates a sharp change in the tilt angle at a temperature of 750 ˚C (Fig. 3). At the same time, the dominant position of the copper atoms in the crystal lattice changes from sites tetrahedrally coordinated by tellurium (tetrasites) at a temperature of 250 - 750 ˚C, to sites octahedrally coordinated by tellurium (octa-sites) at a higher temperature.

6

Figure 3. The copper content “x” in the CuxZrTe2, defined from the crystal structure refinements for the samples, annealed at the corresponding temperatures and quenched.

In situ time-resolved SR-XRPD experiments of Cu0.2ZrTe2 were performed for a more detailed study of these changes in the copper coordination. The Cu0.2ZrTe2 chemical composition was chosen for these experiments because it is close to the center of the two-phase region ZrTe2/CuxZrTe2 and this provides more a correct determination of the phase fractions. Since the synthesis was carried out at a temperature of 1000 ˚C, the starting state of the sample corresponded to that of the sample, quenched from 1000 ˚C. Obviously, this state is the nonequilibrium one. Tables 3, 4 and right panel of figure 2 show the parameters obtained from the refinement of the in-situ X-ray patterns. Heating to 250 ˚C leads to a gradual establishment of equilibrium, however, it is not clear whether the exposure at this temperature is long enough to achieve a true equilibrium state. The discrepancy in the phase composition with the data obtained for the quenched samples indicate an insufficient duration of exposure in the in situ experiments. However, the main trends coincide for the samples obtained in both ways. In both cases, the content of the intercalation phase decreases upon heating. This is in a good agreement with the CuxZrTe2 / ZrTe2 equilibrium boundary. Indeed, a decrease in the amount of the intercalation phase in the quasi-binary case should lead to an increase in the copper content in it. Heating is expected to lead to an increase in the amount of ZrTe2, on the 7

contrary we observed a decrease in its weight fraction and the appearance of ZrTe3 and Zr5Te4 at 750 ° C. Table3. The crystal structure parameters for the Cu0.2ZrTe2 obtained from the refinement of the in-situ x-ray diffraction patterns. Atom

X

y

z

Fract.

Mult.

25˚C

Zr

0

0

0

1

1

RF2=14.34 %

a = 3.9563(1) Å

Te

⅓

⅔

0.2700(4)

1

2

wRp =15.50 %

c = 6.6322(1) Å

Cu

0

0

½

0.51(3)

1

Rp =11.87 % χ2 =1.352

250˚C

Zr

0

0

0

1

1

RF2=18.69 %

a = 3.9650(1) Å

Te

⅓

⅔

0.270(1)

1

2

wRp = 16.52 %

c = 6.6545(3) Å

Cu

0

0

½

0.11(1)

1

Rp = 12.57 %

Cu

⅓

⅔

0.624(6)

0.18(1)

2

400˚C

Zr

0

0

0

1

1

RF2=14.68 %

a = 3.9687(2) Å

Te

⅓

⅔

0.271(1)

0.787(7)

2

wRp = 17.29 %

c = 6.6619(6) Å

Cu

⅓

⅔

0.65(1)

0.12(1)

2

Rp = 13.41 %

Zr

⅓

⅔

0.73(5)

0.017(8)

2

750 ˚C

Zr

0

0

0

1

1

RF2= 32.16 %

a = 3.9985(1) Å

Te

⅓

⅔

0.268(2)

1

2

wRp = 25.50 %

c = 6.7428(4) Å

Cu

0

0

½

1

Rp = 19.92 %

χ2 = 1.603

χ2 = 1.485

χ2 = 1.562

0.6(1) Cu

⅓

⅔

0.650(8)

0.75(9)

2

900 ˚C

Zr

0

0

0

1

1

RF2= 41.08 %

a = 4.0099(3) Å

Te

⅓

⅔

0.264(2)

1

2

wRp = 30.18 %

c = 6.7636(9) Å

Cu

0

0

½

0.10(5)

1

Rp = 23.70 %

Cu

⅓

⅔

0.67(1)

0.19(4)

2

χ2 = 1.464

Table 4. Phase distribution in the Cu0.2ZrTe2 in the in- situ experiments. T, ˚C

25 ˚C

250˚C

400˚C

750˚C

900˚C

CuxZrTe2

42.7 %

43.2 %

33.0 %

9.9 %

39.3 %

ZrTe3

3.0(1) %

10.3(3) %

-

-

-

ZrTe3 (inverse)

4.1(1) %

6.1(2) %

56.0(4) %

76.4(6) %

48(1) %

ZrTe2

50(1) %

39(1) %

-

-

-

ZrSiO4

0.5(1) %

-

1.4(1) %

-

-

ZrO2

-

1.2(1) %

2.4(2) %

2.9(3) %

1.6(4) %

Cu1.4Te

-

-

5.0(3) %

CuTe

-

-

-

1.9(2) %

8

SiO2

-

-

-

7(1) %

12(2)

Zr5Te4

-

-

-

2.3(3) %

-

Te

-

-

2.2(2) %

-

-

This suggests a possible instability of ZrTe2 in this temperature range. In order to clarify this question, the ZrTe2 was annealed in a quartz ampoule at a temperature of 600 °C for a week. The used ZrTe2 was in the form of a pressed tablet and a powder. Figure 4 shows the experimental and calculated X-ray diffraction pattern for a pressed tablet.

Figure 4. The experimental and calculated X-ray diffraction patterns of ZrTe2 after annealing at 600 °C for a week. The difference curve between calculated and observed pattern is shown at the bottom. The fragment with the largest discrepancy between the experimental and theoretical curve is shown in the inset, RF2 = 4.88 %, χ2 = 1.292. Zr1.1(2)Te2, P-3m1, a= 3.9459(1) Å, c = 6.6195(3) Å, weight fraction = 45.6 %. Atom

x

y

z

Fraction

Mult.

Zr

0

0

0

1

1

Te

⅓

⅔

0.2722(4)

1

2

Zr

⅓

⅔

0.63(2)

0.05(1)

2

ZrTe3 (=Zr2Te4.3) a = 5.8866(4) Å, b = 3.9192(4) Å, c = 10.096(1) Å, β=98.14(1), weight fraction = 9

54.4(3)%, space group P21/m

It was found that a partial decomposition of ZrTe2 with the formation of ZrTe3 occurred in the pressed tablet. The crystal structure of the ZrTe3 is characterized by high defectiveness in tellurium sublattice, as a result of which the composition of this phase is close to ditelluride (Fig4). In the powder sample, we found the presence of zirconium oxides and silicides along with elemental tellurium. It is obvious that oxides and silicides were formed as a result of the reaction of the sample with the quartz ampoule. However, these reactions were never observed previously at the synthesis of zirconium ditelluride and its intercalation compounds. Probably, in this case, this reaction was caused by the dispersed form of the lower tellurides which appeared upon the disproportionation reaction. In the case of the pressed tablet the contact area of the sample with the ampoule walls was negligible and, consequently, no reaction between ZrTe2 and ampule (SiO2) was detected. Let us to discuss the reason of the increase in the width of the two-phase ZrTe2/CuxZrTe2 region upon heating from 250 to 750 ˚С. Probably, it is due to the change in the ratio of copper atoms, octahedrally and tetrahedrally coordinated by tellurium, and, as a result, to the change in hybridization (from Cu 3d/Cu 4s/Zr 4d to Cu 3d/Cu 4s/Te 4p). The formation of the two phase region of MyTX2/TX2 upon intercalation of the M atoms was observed in related materials [26–29] . Such behavior was associated with the formation of impurity bands, in our case, such bands can be Cu 3d/Cu 4s/Zr 4d and/or Cu 3d / Cu 4s / Te 4p, which are above the Fermi level of the starting ZrTe2. The shape of the temperature dependence of the ZrTe2/CuxZrTe2 equilibrium boundary in Fig.3 suggests a general scheme for the formation of a chemical bond in the CuxZrTe2, which determines the phase diagram of this material. From a geometrical point of view (Fig. 1) the Cu3d/Cu4s/Te4p hybrid states prevail in the phase in which the Cu atoms are predominantly tetrahedrally coordinated by the Te atoms, whereas the Cu3d / Cu4s / Zr4d hybrid states prevail in the case of octahedral coordination. The Cu3d/Cu4s/Te4p hybrid states should have a lower energy than the Cu3d/Cu4s/Zr4d hybrid states, since the metal-metal bond cannot be energetically more favorable than the metal-chalcogen bond. A two-phase region is observed at room temperature. The ZrTe2 and CuxZrTe2 phases are observed in this region. This situation is typical for the intercalation systems in which there is a band of localized states slightly above the Fermi level of the starting ZrTe2 [30]. The occupation of tetrahedral sites by the copper atoms indicates that this band can be associated with the Cu3d/Cu4s/Te4p hybrid states. This agrees with the structural data obtained for a slowly cooled sample, see Table 2. According to the model of the phase diagrams of similar intercalation compounds [31], the condition for phase stabilization is filling of the impurity band by half. Consequently, the 10

composition of the CuxZrTe2 phase, which is in equilibrium with ZrTe2, corresponds to the half-filled band of the Cu3d/Cu4s/Te4p hybrid states (fig 5a). Heating leads to a smearing of the Cu atoms local environment and, as a result, to the broadening of the Cu3d/Cu4s/Te4p band. At the same time similar smearing of the Cu3d/Cu4s/Zr4d band occurs. In the case when the difference between the energies of the Cu3d/Cu4s /Zr4d and Cu3d/Cu4s/Te4p bands is small, the overlap of these bands should be expected at high temperatures. In this case this combined band will be less than half filled. This configuration will become unstable. The configuration in which the band is half full will be stable. Stabilization of this phase requires a larger amount of electrons, and, consequently, a higher concentration of the Cu atoms, which act as an electron source (fig 5b). It should be noted that when the concentration of copper is more than necessary to stabilize the phase, excessive copper atoms are excluded from the lattice, and this is actually observed (Fig. 2 and Table 2). The Cu1.4Te2 phase was found. The increase in temperature from 250 to 750 ˚C leads to a decrease in the concentration of Cu1.4Te2 and to an increase in the copper concentration in the main phase. Subsequent thermal broadening leads to the overlapping of the Cu3d/Cu4s/Zr4d and Cu3d/Cu4s/Te4p bands (fig. 5c). It allows occupation of the Cu3d/Cu4s/Zr4d states, which correspond to the octahedral coordination of copper by tellurium. The above scheme describes the observed slope of the ZrTe2/CuxZrTe2 equilibrium boundary.

11

Figure 5. The scheme of the hybrid states bands layout of copper with the nearest environment of the ZrTe2 lattice, which explains the observed features of the phase diagram of the Cu-ZrTe2 system.

Conclusions The phase stability of the CuxZrTe2 (0
12

Acknowledgments The in-situ high-temperature XRPD experiments were performed at the MCX beamline of Elettra-Sincrotrone Trieste (project No. 20180056). The authors are grateful to Shared Service Centre ‘Ural-M’, Institute of Metallurgy of the Ural Branch of the Russian Academy of Sciences, for the room-temperature diffraction experiments. Funding for this research was provided by: Russian Science Foundation (project No. 17-7310219).

Compliance with ethical standards Conflict of Interest: The authors declare that they have no conflict of interest.

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Instability of the homogeneous state of CuxZrTe2 at x < x0 has been discovered Temperature dependence of stability boundary of homogeneous state has been determined It was found that at T < 800 C copper atoms are distributed over tetrahedral sites The transition of copper atoms to octahedral sites has been observed at T> 800 C Change in Cu coordination is accompanied by a kink in the ZrTe2/CuxZrTe2 boundary Phase diagram is explained taking into account characteristics of the chemical bond Instability of ZrTe2 accompanied by decomposition on ZrTe and ZrTe3 was discovered

Alexey S. Shkvarin: Data curation, Formal analysis, Software, Supervision, Visualization, Writing - original draft Alexey A.Titov: Resources Mikhail S. Postnikov: Data curation, Software, Visualization Jasper R. Plaisier: Data curation, Formal analysis, Software, Validation, Writing - original draft Lara Gigli: Data curation, Formal analysis, Software, Writing - original draft Mattia Gaboardi: Data curation, Formal analysis, Software, Writing - original draft Alexander N. Titov: Conceptualization, Project administration, Validation, Writing - original draft, Writing - review & editing Elena G. Shkvarina: Conceptualization, Formal analysis, Funding acquisition, Investigation, Methodology, Software, Writing - original draft, Writing - review & editing

Declaration of interests ☒ The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper. ☐The authors declare the following financial interests/personal relationships which may be considered as potential competing interests: