Glass-formation in the GeSe2–Sb2Te3–CdSe system

Journal of Non-Crystalline Solids 356 (2010) 2728–2733

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Journal of Non-Crystalline Solids j o u r n a l h o m e p a g e : w w w. e l s ev i e r. c o m / l o c a t e / j n o n c r y s o l

Glass-formation in the GeSe2–Sb2Te3–CdSe system V. Vassilev a, M. Radonova a, S. Boycheva b,⁎ a b

University of Chemical Technology and Metallurgy — Sofia, Department of Semiconductors 8 Kliment Ohridsky Blvd., 1756 Sofia, Bulgaria Technical University of Sofia, Department of Thermal and Nuclear Power Engineering, 8 Kliment Ohridsky Blvd., 1000 Sofia, Bulgaria

a r t i c l e

i n f o

Article history: Received 4 January 2010 Received in revised form 2 September 2010 Available online 11 October 2010 Keywords: Amorphous materials; Chalcogenides; Glasses; Thermal properties

a b s t r a c t Chalcogenide glasses (ChGs) from the GeSe2–Sb2Te3–CdSe system were synthesized and the glass-forming region was determined by visual examination, X-ray diffraction and electron microscope analyses. The basic physicochemical parameters, such as: density (d), microhardness (HV) and the phase transformation temperatures (glass-transition Tg, crystallization Tcr and melting Tm) were measured. The Hruby's criterion (KG), compactness (C) and some thermomechanical characteristics, such as: volume (Vh) and formation energy (Eh) of microvoids in the glassy network, as well as the module of elasticity (E) were calculated. The density, microhardness and Tg for the investigated ChGs are within the limits of 4.34–5.24 g cm− 3, 791.8– 1078.0 MPa and 509–598 K, respectively. The mean values of the total bond energy bEN, coordination number bZN, bond energy of the average cross-linking per atom Ēc and that of the “remaining matrix” Ērm were determined. The average heteropolar bond energy Ehb and the degree of “cross-linking per atom” P were also calculated. © 2010 Elsevier B.V. All rights reserved.

1. Introduction The increased research interest to the chalcogenide glasses (ChGs) is provoked by their unique properties, which reveal perspectives for many advanced practical applications of these materials. ChGs are well-known optical materials suitable for IR fibers with ultra-low optical losses [1,2], waveguides [3,4] and ultra sensitive optical fiber sensors [3,5,6] due to their large optical window extended to the midinfrared spectral region and high refractive index. The non-linear optical properties observed for these materials are utilized in alloptical switching devices [7], while the photoinduced effects registered accompanied by structural transformations and considerable changes in the optical constants and band-gap energy are successfully applied for holographic information recording, creation of highefficiency holographic diffraction gratings and functional components in the integral optoelectronics [3]. Due to their chemical resistance to aggressive media, the ChGs are preferred membrane materials in potentiometric chemical sensors, microsensors and multisensor systems reversible to metal ions in water solutions [8–10]. Chemical sensors based on ChGs superior their polycrystalline analogous with respect to their time of life, sensitivity and selectivity in acidic and redox media [11]. As a rule, ChG membranes are reversible to the metal ions included in their composition, as well as significant ionic conductivity is required as a prerequisite for their ion-exchange ability. ⁎ Corresponding author. E-mail addresses: [email protected] (V. Vassilev), sboycheva@tu-sofia.bg (S. Boycheva). 0022-3093/$ – see front matter © 2010 Elsevier B.V. All rights reserved. doi:10.1016/j.jnoncrysol.2010.09.052

The multicomponent chalcogenide GeSe2–Sb2Te3–CdSe system attracted our scientific interest because of the appropriate combination of the constituents: GeSe2 is an excellent glass-former; Sb2Te3 is a network-modifier, which cross-links the glassy network; and the GeSe2–Sb2Te3 couple could dilute significant amount of CdSe. It could be expected that the suggested ChGs will be suitable for creation of Cd (II)-ion-selective chemical sensors because of the incorporation of cadmium in the glassy network, which will govern the membrane reversibility. In addition, the cross-linked glassy structure is a prerequisite for stronger selectivity. Moreover, the higher number of components exceeds the glass-forming ability and stability against crystallization, and it could be expected that the suggested glasses will possess significant thermal durability, which is of substantial importance for their further application. The present paper is emphasized on the determination of the glass-forming region in the GeSe2–Sb2Te3–CdSe system, investigation of some basic application-relevant properties and structural parameters of the glasses obtained.

2. Experimental procedures The glass-forming region in the GeSe2–Sb2Te3–CdSe system was delineated by the synthesis of 26 compositions. The samples from the GeSe2–Sb2Te3–CdSe system, as well as the initial compounds GeSe2 and Sb2Te3 were produced by direct mono-temperature synthesis [12] in evacuated to residual pressure of 0.133 Pa and sealed quartz ampoules. GeSe2 and Sb2Te3, as starting compounds for the synthesis of ternary alloys, were obtained from Ge, Se, Sb and Te of 5 N purity,

V. Vassilev et al. / Journal of Non-Crystalline Solids 356 (2010) 2728–2733

while commercial CdSe (suprapur) product of the MERCK Company was also used. The following synthesis conditions were applied: three-stage temperature increase up to 923, 1073 and 1293 K, at rates of 3–4, 2– 3 and 2–3 K min− 1, respectively; homogenizing annealing at these temperatures for 0.5, 0.5 and 2 h, correspondingly; continuous vibration stirring of the melt at the highest temperature was performed; finally, the melts were solidified by quenching in a mixture of water and ice. The synthesized samples were subjected to visual, microscope and X-ray diffraction analyses to judge their glassy or/and crystalline state. The following physicochemical properties for the synthesized ChGs from the GeSe2–Sb2Te3–CdSe, system were studied: microhardness HV — by the Vickers method (microscope MIM-7 and microhardness meter PMT-3 at loading of 10 g); density d — by hydrostatic method with toluene as a reference liquid; characteristic temperatures: glasstransition Tg, crystallization Tcr and melting Tm — by differential thermal analysis (DTA). DTA was carried out using the F.Paulik-J. Paulik-L.Erdey, MOM-Hungary equipment under the following procedure: quantity of 0.3 g of the examined samples and a reference substance was evacuated and sealed in Stepanov's quartz containers and heated at a rate of 10 K min− 1. γ-Al2O3, preliminary tempered to avoid any adsorbed moisture and volatile impurities, was used as a reference substance. HV and d values were measured with ±5 in accuracy and the characteristic temperatures — with ± 5 K in accuracy. The X-ray diffraction analysis (XRD) was performed by X-ray diffractometer TUR-M61 with CuKα-radiation and Ni-filter, θ = 5–40°.

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Fig. 1. XRD patterns of samples in the GeSe2–Sb2Te3–CdSe system: a) glass — (GeSe2)72 (Sb2Te3)18 (CdSe)10; b) glass + crystal — (GeSe2)56 (Sb2Te3)24 (CdSe)20; c) crystal — (GeSe2)58.5 (Sb2Te3)31.5 (CdSe)10.

3. Results The nominal compositions and the state of all synthesized samples from the GeSe2–Sb2Te3–CdSe system are listed in Table 1. Visual examination revealed that the glassy alloys are dark in color with characteristic gloss and conchoidal fracture of the freshly exposed surfaces. The obtained samples we classified as amorphous, crystalline and amorphous + crystalline by XRD analysis. Typical XRD patterns are shown in Fig. 1. The XRD reveals that the compositions located in the glass-forming region possess the typical patterns for amorphous state — presence of amorphous plateau and absence of specific diffraction reflection (Fig. 1,a). For the compositions located on the glass-formation/ crystalline matter boundaries, the XRD patterns are considerably richer in diffraction peaks although of lower intensity (Fig. 1,b), while for those outside the glass-forming area, the diffraction patterns are typical of crystalline states (Fig. 1,c). The analysis of the line-diagrams (Fig. 2) shows that in the ChGs of the GeSe2–Sb2Te3–CdSe system the phases CdSe and GeSe2 crystallize

Fig. 2. XRD line-diagrams of compositions in the studied system: p.4 — (GeSe2)56 (Sb2Te3)24 (CdSe)20; p.10 — (GeSe2)58.5 (Sb2Te3)31.5 (CdSe)10; p.21— (GeSe2)61.2 (Sb2Te3)10.8 (CdSe)28; 4 — CdSe [14]; 5 — GeSe2 [15]; 6 — γ Sb, Te [16]; 7 — Te [17].

predominantly. Restricted number of SbTe and Te (Sb2Te3 → 2SbTe + Te) lines are observed. Both the numbers of lines and their intensities grow with the increase of Sb2Te3 concentration in the ChGs. Our expectations for dissociation according to the reaction GeSe2 → GeSe + Se at higher GeSe2 contents are not verified experimentally in the present work. Most probably, distortion of the Te–Te bonds could occurred because the bond strength decreases in the order Se–Se N Se–Te N Te–Te. On the basis of the visual and X-ray diffraction analyses, the glass-forming region in the (GeSe2) x(Sb2 Te3)y(CdSe)z system,

Table 1 Nominal compositions and status of the synthesized samples in the (GeSe2)x(Sb2Te3)y(CdSe)z system. No.

1 2 3 4 5 6 7 8 9 10 11 12 13

Nominal composition, mol%

State

GeSe2

Sb2Te3

CdSe

90 81 72 56 54 50 55 80 72 58.5 59.5 60 64

10 9 8 24 36 50 45 20 18 31.5 25.5 20 16

0 10 20 20 10 0 0 0 10 10 15 20 20

Glass Glass Glass Glass + crystal Crystal Crystal Crystal Glass Glass Crystal Glass + crystal Glass Glass

No.

14 15 16 17 18 19 20 21 22 23 24 25 26

Nominal composition, mol%

State

GeSe2

Sb2Te3

CdSe

60 67.5 63.75 63 65 80.75 76 61.2 56.25 70 83.3 78.4 100

15 7.5 21.25 27 35 4.25 4 10.8 18.75 30 1.7 1.6 0

25 25 15 10 0 15 20 28 25 0 15 20 0

Glass Glass + crystal Glass Glass Crystal Glass Glass Glass + crystal Glass + crystal Glass + crystal Glass + crystal Glass Glass

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V. Vassilev et al. / Journal of Non-Crystalline Solids 356 (2010) 2728–2733

where x + y + z = 100 mol% and m = y/(x + y), was defined (Fig. 3). It extends towards the GeSe2 area and partially lies on the Sb2Te3– GeSe2 (70–100 mol% GeSe2) and GeSe2–CdSe (0–10 mol% CdSe) sides in the Gibb's concentration triangle. In the binary CdSe–Sb2Te3 system, glass-formation was not observed. Typical DTA curves are plotted in Fig. 4. The obtained values of the thermal characteristics: Tg, Tcr and Tm for the investigated glassy alloys are summarized in Table 2. The results from the measurements of d and HV, as well as the calculated KG are also listed in Table 2. The modulus of elasticity (E), the minimum volume (Vh) of the microvoids and the energy for their formation (Eh), the Hruby's criterion KG and the compactness C are calculated by Eqs. (1)–(3) [13]:

E = 15HV;

KG =

Vh = 5:04

Tg ; HV

Eh = 30:729Tg

T cr T g T m T cr

  −1 Mx Mx ; C = d ∑ i i  ∑ i i ∑Mi xi di d i i i

ð1Þ

ð2Þ

ð3Þ

where: Tg, Tcr and Tm — temperatures of glass-transition, crystallization and melting; Mi and xi — the molar mass and the molar percentage of the i-th component. The compositional dependences Vh (m,z), Eh (m,z), C (m,z) and E (m,z) are presented in Figs. 5–8, correspondingly. 4. Discussion The thermal effects related to the crystallization and melting processes are apparently larger than that related to the softening. The glass-transition temperature Tg depends on the glass composition (Table 2), as the effect of Sb2Te3 being definitely stronger. The introduction of CdSe (at constant Sb2Te3 content) results in a slight decrease of Tg. Such an effect should be expected considering that the metal part of the chemical bond in GeSe2 is considerably lower than that in CdSe and Sb2Te3. Sb2Te3 causes stronger structural reorganization compared to CdSe because of the incorporation of two different elements (Sb and Te) into the glassy network and the appearance of pyramidal structural units SbTe3/2. In addition, Sb2Te3 behaves as modifier in the investigated system improving the GeSe2 glassformation ability analogy to the couple GeSe2–Sb2Se3 [13,18].

Fig. 4. Thermograms of ChGs from the GeSe2–Sb2Te3–CdSe system: 1 — (GeSe2)81 (Sb2Te3)9 (CdSe)10; 2 — (GeSe2)72(Sb2Te3)18(CdSe)10; 3 — (GeSe2)80(Sb2Te3)20 (CdSe)0.

The crystallization temperature Tcr widely varies depending on the Sb2Te3 content (Table 2). Besides the effect of the strengthening of the metal part in the chemical bond, the crystallization is influenced on the increase in the SbTe3/2 structural unit content. Tcr negligibly varies adding CdSe at m = const. CdSe forms linear structural units –Cd–Se–, and their content elevation does not cause substantial structural changes in the ChG network. Tm depends slightly on the ChG composition due to the close values of the melting temperatures for GeSe2 and Sb2Te3, and most probably corresponds to the melting of crystallized solid solutions between GeSe2 and Sb2Te3, whose solubility curve slightly depends on T. The microhardness of the examined samples is in the range 791.8– 1078.0 MPa and depends logically on the glass compositions (Table 2) taking into account that HVGeSe2 N HVCdSe(HVSb2Te3) − HVGeSe2 = 980– 1960 MPa [19], HVCdSe = 882–1274 MPa [20] and HVSb2Te3 = 176.4 MPa [21]. The compositional dependences of E(m) and Eh(m) at z = const, and of E(z) and Eh(z) at m = const follow the analogical trends to those of HV(m) and Tg(m) at z = const, and of HV(z) and Tg(z), at m = const, respectively, according to the Eq. (1). The minimum volume of the microvoids varies in the range ≈ (27–32).10− 3 nm3, depending on the glass composition (Table 2, Fig. 5). The increase of Sb2Te3 content at a constant CdSe molar percentage (z = const) leads to a smooth increase in the Vh(m) function, while Vh(z) at m = const is almost linear. When the content of Sb2Te3 and CdSe in the glassy allows increases at z = const and m = const, respectively, the average molecular mass ¯ and the X-ray density (dR) grow, according to the Eq. (4): M

dR =

Fig. 3. Glass-forming region in the multicomponent GeSe2–Sb2Te3–CdSe system.

¯ mH zM ; V

ð4Þ

¯ -average molecular where: z-number of atoms in the unit cell; M mass; mH-hydrogen atomic mass; V-volume of the unit cell.

V. Vassilev et al. / Journal of Non-Crystalline Solids 356 (2010) 2728–2733

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Table 2 Physicochemical properties of glasses in the system (GeSe2)x(Sb2Te3)y(CdSe)z. No.

1 2 3 4 5 6 7 8 9 10

Nominal composition, mol% x

y

z

100 90 80 81 72 63 76 72 64 60

0 10 20 9 18 27 4 8 16 20

0 0 0 10 10 10 20 20 20 20

m

Tg, K

Tcr, K

Tm, K

d, g cm− 3

HV, MPa

KG, –

0.00 0.10 0.20 0.10 0.20 0.30 0.05 0.10 0.20 0.25

598 558 533 555 525 509 553 548 519 512

828 668 625 663 620 533 658 649 615 553

990 750 745 745 735 725 735 736 726 718

4.34 4.53 4.72 4.72 4.89 5.09 4.74 4.90 5.14 5.24

1078 897 825 916 834 792 981 941 840 817

1.45 1.36 0.77 1.32 0.83 0.13 1.36 1.16 0.86 0.25

Eq. (4) refers to the crystalline state of the substances but it could be assumed for the glassy samples of the investigated system, i.e. it could be expected that d will follow the same pattern as dR, as the ratio between the density of the crystalline (dcr) and glassy state (dR N dcr N d) is preserved. This assumption was experimentally proved by the measured values for d of the investigated ChGs (Table 2) and the calculated values for their crystalline analogous. As d = m/(Vh + Vglass), where Vh and Vglass are the volumes of the microvoids and the glass, respectively, then the addition of Sb2Te3 (CdSe) in certain concentration ranges will most probably cause a densification of the glassy structure, i.e. d increases because of the decrease in Vglass and Vh + Vglass (the covalent radii of the elements building the glassy network are in the following ratios: rGe b rSb b rCd; rSe b rTe). The compactness of the studied ChGs is slightly influenced by the Sb2Te3 and CdSe concentration, while their glass-formation ability evaluated by Hruby's criterion is strongly dependent on the Sb2Te3 content (accounted by the m ratio at z = const) and negligibly — on the CdSe (expressed by the molar percentage z at m = const). Practically, the compactness does not change increasing the Sb2Te3 (CdSe) content in the glassy alloys. As it was mentioned above, the atomic mass and the radius of Ge and Se are smaller than those of Sb(Cd) and Te, respectively. It could be expected, that due to the difference in the atomic radii the structure densifies and the volume decreases when

the Sb2Te3 and CdSe concentrations are increased. In addition, Sb2Te3 and CdSe possess greater density than that of the GeSe2, and the glass density grows elevating their content, while the volume Vglass decreases. According to Eq. (3), the C values will be preserved as Vglass and V V decrease but their ratio Vglass/V remains constant (C= glass V −1). The Sb2Te3 addition significantly decreases the glass-forming ability of the chalcogenide system due to the increase of the metal part of the chemical bond and the effect on crystallization of the pyramidal structural units. The Sb2Te3 behaves as a weaker modifier than Sb2Se3 [13,18] but in spite of that the glass-forming GeSe2–Sb2Te3 couple dissolves significant quantities of CdSe (≤28 mol% CdSe). The CdSe slightly affects KG at m = const because the linear fragments –Cd–Se– of CdSe integrate in the linear sections of the structural GeSe4/2 and SbTe3/2 units or in the linear chains connecting these structural units. Comparatively high values for KG for the glasses could be indicative for an existence of triple eutectic point in the pseudo-ternary system [22,23]. An additional evidence for existence of eutectic compositions could be Tg variation in a wide range. The properties of the ChGs depend on the overall mean bond energy which is a function of the average coordination number, the type and energy of the chemical bonds between the atoms building their structural network. The average coordination numbers bZN for the studied glassy compositions expressed for convenience as Gex′Sby′Cdz′Tew′Sev′, where

Fig. 5. Dependence of Vh on the composition of the (GeSe2)x(Sb2Te3)y(CdSe)z glasses.

Fig. 6. Compositional dependence of Eh for the (GeSe2)x(Sb2Te3)y(CdSe)z glasses.

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where: P — degree of cross-linking per atom; Ehb — average heteropolar bond energy of ChGs with compositions Gex′Sby′Cdz′ Tew′Sev′, calculated by means of Eq. (8): Ehb = ðx′ Z A EA–D + y′ Z B EB–D + z′ Z C EC–D + x0 Z A E

A–E +

y′ Z E

B B–E

+ z′ ZC EC–E Þ

= ðx′ ZA + y0 Z B + z′ Z C Þ ð8Þ where: EA–D, EB–D, EC–D, EA–E, EB–E and EC–E — heteropolar energy of the bonds Ge–Te, Sb–Te, Cd–Te, Ge–Se, Sb–Se and Cd–Se — Table 3. The coefficient R, which determines the chalcogen content in the glasses, is determined by Eq. (9): R = ðw′ ZD + v′ ZE Þ = ðx′ ZA + y′ ZB + z′ ZC Þ:

ð9Þ

In the case of R N 1, the glasses are enriched in chalcogen and possess both heteropolar and chalcogen–chalcogen bonds, which is typical for the compositions without CdSe. By them the degree of cross-linking per atom Pr (P = Pr, for R N 1) can be calculated by Eq. (10): Fig. 7. Dependence of C on the composition of the (GeSe2)x(Sb2Te3)y(CdSe)z glasses.

Pr = ðx′ ZGe + y′ ZSb + z′ ZCd Þ = ðx′ + y′ + z′ + w′ + v′ Þ:

ð10Þ

The average bond energy Ērm (R N 1) is: x′ + y′ + z′ + w′ + v′ = 1, were calculated by Eq. (5), as suggested by Tanaka [24]: bZN = x′ ZGe + y′ ZSb + z′ ZCd + w′ ZTe + v ′ ZSe :

ð5Þ

The following coordination numbers of the composing elements were used: ZGe = 4, ZSe = 2 [25] and ZTe = 2 [26] , ZSb = 3 [27], ZCd = 4 [28]:The mean values of the total bond energy bEN were calculated by Eq. (7), suggested by Tichy [29] for complex chalcogenide systems: b EN = Ēc + Ērm ;

ð6Þ

where: Ēc — bond energy of the average cross-linking per atom calculated by Eq. (7): Ēc = P:Ehb ;

ð7Þ

Ērm = 2ð0:5b Z N –Pr ÞðEEE + ED–D Þ = b Z N ;

ð11Þ

where EE–E and ED–D are the bond energy of Se–Se and Te–Te, respectively. The compositions with R = 1 are stoichiometric and contain only heteropolar bonds. When R b 1, the glasses are deficient in chalcogen and possess heteropolar and metal–metal bonds which is typical for the compositions having 10–20 mol% CdSe. In this case the degree of cross-linking per atom Pp (P = Pp, for R b 1) can be calculated by Eq. (12): Pp = ðv′ ZSe + w′ ZTe Þ = ðx′ + y′ + z′ + w′ + v′ Þ:

ð12Þ

The average bond energy per atom of the “remaining matrix” Ērm (R b 1) is given by: Ērm = 2ð0:5bZ N –Pp ÞEb N = bZ N

ð13Þ

Eb N = ðEA–A + EB–B + EC–C + EA–B + EA–C + EB–C Þ = 6:

ð14Þ

In Eq. (14), EbN is the average bond energy of Me–Me (Me + Me′) in the chalcogen deficient part of the glass-forming area, and EA–A, EB–B, EC–C, EA–B, EA–C and EB–C are the bond energy of Ge–Ge, Sb–Sb, Cd–Cd, Ge–Sb, Ge–Cd and Sb–Cd, respectively — Table 3. The values for bZN, Ēc, Ērm and bEN are summarized in Table 4. The results presented in Table 4 indicate that the mean values of the total bond energy bEN, as well as of its components — Ēc and Ērm, depend on the glass composition which is represented by the average coordination number bZN. Table 3 Bond energy of glasses in the GeSe2–Sb2Te3–CdSe system.

Fig. 8. Compositional dependence of E for the (GeSe2)x(Sb2Te3)y(CdSe)z glasses.

Bond

Ge–Ge

Ge–Sb

Ge–Cd

Ge–Se

Ge–Te

Sb–Sb

Sb–Cd

Sb–Se

E, eV Ref.

1.63 26

1.48 26

1.08 22

2.12 26

1.78 27

1.31 26

1.61 22

1.86 26

Bond

Sb–Te

Cd–Cd

Cd–Se

Cd–Te

Se–Se

Se–Te

Te–Te

E, eV Ref.

2.88 28

0.08 29

1.32 30

1.04 30

1.90 26

1.94 27

1.47 27

V. Vassilev et al. / Journal of Non-Crystalline Solids 356 (2010) 2728–2733 Table 4 Physicochemical properties of samples of the GeSe2–Sb2Te3–CdSe (Ge′Sb ′Se′) x ′Cd y ′Te z w v system. No.

1 2 3 4 5 6 7 8 9 10

Composition, mol% x′

y′

z′

w′

v′

0.33 0.28 0.23 0.26 0.22 0.18 0.26 0.24 0.21 0.19

0 0.06 0.12 0.06 0.11 0.16 0.03 0.06 0.10 0.12

0 0 0 0.03 0.03 0.03 0.07 0.07 0.06 0.06

0 0.1 0.18 0.09 0.17 0.23 0.04 0.08 0.15 0.19

0.67 0.56 0.47 0.56 0.47 0.4 0.6 0.55 0.48 0.44

b ZN

Ēc, eV

Ērm, eV

bEN, eV

2.66 2.62 2.58 2.64 2.61 2.58 2.69 2.68 2.65 2.62

2.80 5.23 5.30 5.03 5.05 5.11 4.67 4.70 4.74 4.85

0.01 0.02 0.03 0.02 0.03 0.03 0.06 0.06 0.07 0.04

2.81 5.25 5.33 5.05 5.08 5.14 4.73 4.76 4.81 4.89

When the chalcogen Se(Te, Se+Te) content in the multicomponent ChGs is increased, bZN decreases and the heteropolar bond formation is stipulated (Eq. (8)). The energy of these bonds is higher than that of all possible metal–metal bonds (Table 3), that is why the total bond energy bEN increases when the average coordination number bZN decreases. 5. Conclusions The glass-forming region in the GeSe2–Sb2Te3–CdSe system has been defined. It is extended to the GeSe2-rich zone in the Gibbs' diagram and partially located on the sides Sb2Te3-GeSe2 (70–100 mol% GeSe2) and GeSe2–CdSe (0–10 mol% CdSe). The main physicochemical parameters (Tg, Tcr and Tm, d and HV) of the obtained ChGs have been measured and have been used as input parameters for calculation of some thermomechanical characteristics (E, Eh, Vh and KG). The glasses from the GeSe2–Sb2Te3–CdSe system allow dissolution of up to 20 mol% CdSe and are characterized with satisfying thermal stability (Tg~ 509–598 K), resistance against crystallization even for the glasses with high metal content (KG = 1.36 for the glass composition (GeSe2)76 (Sb2Te3)4(CdSe)20), densely structure (d~4.34–5.24 g cm− 3) but comparatively low hardness which will render their mechanical shape (HV~791.8–1078.0 MPa; E b 16× 103 MPa). On the base of the obtained results, it could be expected that the suggested glassy alloys will be suitable membrane materials in Cd2+-ion-selective chemical sensors form the “coated-wire” type. Compositional relationship for the physicochemical properties of the studied chalcogenide glasses from the GeSe2–Sb2Te3–CdSe system have been established and discussed in terms of structural parameters (the average coordination number bZN, the total bond energy bEN and its constituents (Ēc, Ērm and Ehb), and the degree of “cross-linking per atom” P).

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