Phase equilibria in the CuInSe2-Ge-Se quasi̇ternary system Текст научной статьи по специальности «Химические науки»

244

CHEMICAL PROBLEMS 2020 no. 2 (18) ISSN 2221-8688

0

UDC 541.123.3

PHASE EQUILIBRIA IN THE CuInSe2-Ge-Se QUASiTERNARY SYSTEM N.M. Allazova1, R.F. Abbasova2, T.M. Ilyasli 2, I.I. Aliyev1, M.R. Allazov 3

1 Acad. M. Nagiyev Institute of Catalysis and Inorganic Chemistry National Academy of Sciences of Azerbaijan 113, H. Javid. ave., AZ1143, Baku, Azerbaijan 2Baku State University, 23, Acad. Z.Khalilov str., AZ 1148 Baku, Azerbaijan 3 Azerbaijan Technical University 25, H. Javid ave., AZ 1073, Baku, Azerbaijan Phone: +994 50 4770082, e-mail: ilkin_m@mail.ru

Received 16.03.2020 Accepted 29.05.2020

Abstract: Phase equilibria in the CuInSe2-Ge-Se ternary system were studied by methods of differential thermal (DTA), X-ray phase (XRD), microstructural (MSA) analyzes and measurement of microhardness. Results of these studies were summarized and presented in the paper. Phase diagrams of CuInSe2-Ge, CuInSe2-GeSe, CuInGeSe4 - Ge, CuInGeSe4 - GeSe, CuInGeSe4 -Se and liquidus surface projections of quasi-ternary system established and monovariant curves, regions of phase delamination in the liquid state, coordinates of monotectic, metathetic, peritectic and eutectic processes determined. Also, a region of primary crystallization of a low-temperature polymorphic form (phase with a chalcopyrite structure) of the CuInSe2 compound in the presence of germanium chalcogenides specified.

Keywords: system, chalcopyrite phase, phase equilibria, liquidus surface projection, chalcopyrite phase, phase transition

DOI: 10.32737/2221-8688-2020-2-244-249

Introduction

The low-temperature chalcopyrite phase of the CuInSe2 compound is of interest as a solar energy converter [1-3]. However, its conversion coefficient strongly depends on imperfections of the crystal structure which are formed mainly during the polymorphic transition of sphalerite o- chalcopyrite. Therefore, to reduce these imperfections, crystallization is carried out by flux method [4-5].

Earlier, we presented results of the study of phase equilibria in the CuInSe2-Sn-Se and CuInSe2-Pb-Se systems where regions of

primary crystallization of a-CuInSe2 directly from the liquid melt were determined [6, 7].

In the present work, the possibility of using germanium and its selenides as solvents for the primary crystallization of the chalcopyrite phase of the CuInSe2 compound was clarified. For this purpose, the pattern of interaction of CuInSe2-Ge-Se system components was determined, especially in areas where the chalcopyrite phase of the CuInSe2 compound was directly crystallized from the liquid melt.

Experimental part

The initial samples for the study were synthesized by fusion from calculated amounts of highly pure elements (copper - grade M0, indium grade In-000, germanium with a resistivity of 40 Ohm cm, selenium grade OSCH 19-4) in evacuated (~ 0.1 Pa) and sealed quartz ampoules at 11000 C for 6 hours. Then the furnace was cooled to 6000 C and stored for

200 hours.

The resulting ingots were equilibrium polycrystals and characterized by differential thermal analysis (DTA) and X-ray diffraction (XRD).

During DTA, the phase transition temperatures were determined using a chromel/alumel thermocouple with a heating

CHEMICAL PROBLEMS 2020 no. 2 (18)

www.chemprob.org

and cooling rate of 10 K/min on a two-coordinate potentiometer N307/1. Calcined aluminum oxide served as a reference.

X-ray powder diffraction patterns were recorded with Bruker D8 diffractometer using CuKa radiation with a nickel filter.

Microstructures of polished samples were examined on a METAM-P1 metallographic microscope, and microhardness measurements carried out on a PMT-3 microhardness tester under a load of 20 g.

Results and discussion

The nature of physicochemical interaction of some sections of the ternary system CuInSe2-Ge-Se is presented below. Also, projections of the liquidus surface were constructed.

The CuInSe2-Ge section is quasibinary. Phase diagram of this section is eutectic, there is a region of immiscibility on the side of germanium (Fig. 1a). The eutectic crystallizes at 50 mol.% Ge and 7900C. The monotectic process occurrs at 8500C in the area of 67-87 mol.% Ge.

The CuInSe2-GeSe section is non-quasi-binary and quasi-stable simultaneously, since

just two phases a-CuInSe2 and a-GeSe are determined in the sub-solidus of the system (Fig. 1b).

Under the influence of germanium mono-selenide, the temperature of the polymorphic transition of the CuInSe2 compound does not change, and the isothermal line of this transition, determined at 8100C, crosses the liquidus at 44 mol.% GeSe. Primary crystallization of the chalcopyrite phase (a-CuInSe2) occurs directly from the liquid melt in the concentration region 44-78 mol% of GeSe.

M-îr

l—a I

- .'»--Ja* w

\

Ii I- <3 I Ê J 'I

L-BXcjèk

«

I

„

ï-u t

HC

v.: >tCii L r A

I- -¡t > V _ V * \ ->

ÎÏÏ "w

L-m-t j UL1 tS t t - J

s * .if

2z~.< It- J»

—

CuiSe: 3C «

tit Oüfic

£ GeSe

■CiOI nCiGili

Fig. 1. Phase diagrams of the CuInSe2-Ge (a) and CuInSe2-GeSe (b) systems.

As is known, GeSe is formed by peritectic between the liquid and germanium. In the section, before intersection of liquidus (a-CuInSe2) curves, the temperature of primary crystallization of germanium decreases from 720 to 6250C. Crystallization in the system is over through four-phase peritectic reaction:

L+ Ge ^a-GeSe at 5750C Solubility based on the starting components is practically absent.

The CuInGeSe4-Ge section is non-quasibinary. According to [8, 9], the CuInGeSe4 compound is formed by the peritectic reaction in the quasibinary CuInSe2-GeSe2 system at 7120C.

The liquidus of the CuInGeSe4-Ge system consists of two primary crystallization curves of a-CuInSe2 and germanium, which intersect at 40 at% Ge and 6400C (Fig.2a).

The CuInGeSe4-GeSe section is non- mol% GeSe and 6600C (Fig. 2b). quasi-binary. The liquidus of the system Crystallization in the system is completed by

consists of two curves of primary crystallization a four-phase peritectic reaction: of a-CuInSe2 and germanium that intersect at 40

L+ a-CuInSe2 o CuInGeSe4 + a-GeSe at 5750C Solubility based on the starting components is practically absent.

t,°C

827 ,

a +CuInGeSe4+ GeSe

CuInGeSe4 20

40 60 at% Ge

t,°C.

827

200 .

^ CuInGeSe4+aGeSe

a +

Ge CuInGeSe4 20

40 60 mol% GeSe

GeSe

Fig. 2. Phase diagrams of the CuInGeSe4 - Ge (a) and CuInGeSe4 - GeSe (b) systems.

The CuInGeSe4-Se section is quasi-stable and participates in the incongruent triangulation of the CuInSe2-Ge-Se ternary system. The liquidus of the system mainly consists of the curve of the primary crystallization of the aphase (the low-temperature polymorphic form of CuInSe2) (Fig. 3). Crystallization in the

system is completed at a temperature of ternary peritectic, 2150C. There is no solubility based on the starting components.

The microhardness of the CuInGeSe4 phase is determined at 300 MPa, and the microhardness of the selenium phase is 450 MPa.

t,°C 827 800 712

600

400

200

' L

L+a \ L+Se

L+a+CuInGeSe4 \ \

215

o 6jo

■ CuInGeSe4+Se L+a+Se

CuInGeSe4 60 70 80 90 Se at% Se

Fig. 3. Phase diagram of the CuInGeSe4 - Se system

The projection of the liquidus surface of the CuInSe2-Ge-Se system (Fig. 4) is constructed on the data of phase diagrams of the above-mentioned sections of the quasi binary systems CuInSe2-GeSe2[8], CuInSe2-Se [10] and Ge-Se [6]. Here, the quasibinary section CuInSe2 -

GeSe2 is a diagonal section and divides the quasi ternary system into two subsystems: CuInSe2 - GeSe2 - Se and CuInSe2 - GeSe2 -Ge.

In the first subsystem, two triple peritectic and one eutectic process were found:

{Pi } L +Ge o CuInGeSe4+GeSe at 5750C {P2 } L + CuInSe2 o CuInGeSe4+Ge at 6300C { Ei} L o CuInGeSe4+GeSe+ GeSe2 at 5600C

As known, metathetic processes in the CuInSe2- In the quasi-ternary subsystem, these Se and Ge-Se systems occur with the immiscible regions merge with each other and

participation of germanium and the form one common immiscible region in the

delamination regions are closer to germanium, liquid state.

Fig. 4. Projection diagram of the liquidus surface of the CuInSe2-Ge-Se system. Primary crystallization field: 1-P-CuInSe2, 2-a-CuInSe2, 3-GeSe2, 4-, 5-CuInGeSe4, 6-Ge, 7-Se

In the first subsystem, P-CuInSe2, a-CulnSe, GeSe2, GeSe and germanium phases are crystallized primarily. A part of the primary crystallization of germanium occurs under monotectic line.

In the second subsystem, the phases P-CuInSe2, a-CuInSe2, GeSe2 and selenium are primarily crystallized. A part of the primary

crystallization of a-CuInSe2 occurrs under delamination. Here crystallization is over at 200° C in a triple eutectic, the composition of which is designated as E2. Prior to this, a four-phase peritectic process of separation of the CuInGeSe4 compound takes place along the isothermal plane at 2150C.

Conclusions

Thus, 7 fields of primary crystallization of CuInSe2 - Ge - Se system and phase equilibria phases are established in the quasi-ternary were studied. The transition boundary of the

primary crystallization fields a-CuInSe2 and P- by blue line (nimmm). CuInSe2 was determined, it is indicated in Fig. 4

References

1. Medvedkin G.A., Terukov E.I., Sato K. et al. Photoluminescent properties of polycrystalline solar cells ZnO / CdS / CuInGaSe2 at low temperature. Semiconductors/physics of the solid state. 2001, vol.35, no.11, p.1385. (In Russian).

2. Modern problems of semiconductor photovoltaics. Fonash S., Ed. T. Kautsa, J. Mirnina. Moscow: Mir Publ., 1988, 307 p.

3. Maronchuk I.I., Sanikovich D.D., Mironchuk V.I. Solar cells: current status and development prospects. Izvestiya Vysshikh Uchebnykh Zavedenii, Energetika -Energetika. Proceedings of CIS higher education institutions and power engineering associations. 2019, vol. 62, no. 2, pp.105123. (In Russian).

4. Preparative methods in solid state chemistry., ed. P. Hagenmuller. Moscow: Mir Publ., 1976, p.208.

5. Zargarova M.I., Babaeva P.K., Azhdarova D.S. et al. Study of CuInSe2-InSe2 (SnSe2, Bi2Se3) systems. Inorganic Materials. 1995, vol. 31, no.2, p.282. (In Russian).

6. Allazova N.M., Abbasova R.F., Ilyasly T.M.

Primary crystallization area of the chalcopyrite phase in the CuInSe2-Sn-Se system. Russian Journal of Inorganic Chemistry. 2011, vol. 56, no. 10, pp.1714-1719.

7. Allazova N.M., Ilyasly T.M. Primary crystallization area of the chalcopyrite phase in the CuInSe2-Pb-Se system. Azerbaijan Chemical Journal, 2015, no. 1, pp. 60-66.

8. Vakulovich A.P., Olekseyuk ID. Phase equilibria in the CuInSe2-GeSe2 and CuInSe2-Cu2GeSe3 sections of the quaternary Cu2Se-In2Se3-GeSe2 system. Alloys and Compounds, 2004, vol. 24, pp. 47-48.

9. Matsushita H., Maeda T., Katsui A., Takizawa T. Thermal Analyses of CuInGeSe4 Quaternary Compound for Crystal Growth by Solution Method. Japanese Journal of Applied Physics. 2000, vol. 39, no.1, p.62.

10. The state diagram of binary metal systems. Directory. / Ed. N.P. Lyakisheva. Moscow, 2001, vol.2, 1024 p.

CuInSe2-Ge-Se KVAZWÇLU SiSTEMiNDd FAZA TARAZLIGI 1N.M. Allazova, 2R.F. Abbasova, 2T.M. ilyasli, 1i.i. dliyev, 3M.R. Allazov

'AMEA-nin Kataliz va Qeyri-uzvi Kimya înstitutu Az 1143, Baki, H. Cavid pr, 113

2Baki Dôvlat Universiteti AZ 1148, Baki, Z. Xalilov kuç, 23 3Azarbaycan Texniki Universiteti Az 1073,Baki, H. Cavid pr., 25 e-mail:allazov_m@mail.ru

Differensial-termiki (DTA), rentgen-faza (RFA), mikroquruluç (MQA) va mikrobarkliyin ôlçulmasi usullari ila CuInSe2-Ge-Se uçlu sisteminin butun qatiliq sahalarinda faza tarazligi ôyranilmiçdir va naticalar umumilaçdirilib va bu maqalada verilir. Kvaziuçlu sistemin CuInSe2-Ge, CuInSe2-GeSe, CuInGeSe4 - Ge, CuInGeSe4 - GeSe, CuInGeSe4 -Se kasiklarinin faza diaqramlari va ôzunun likvidus sathinin ortoqonal proyeksiyasi qurulmuçdur. Sistem daxilinda maye fazada tabaqalaçma sahasi, monovariant ayrilar, monotektik, metatektik, peritektik va evtektik proseslarin koordinatlari tayin edilmiçdir. CuInSe2 birlaçmasinin açagi temperaturlu polimorf formasinin (xalkopirit quruluçlu fazanin) ilkin kristallaçma sahalarina germanium xalkogenidlarinin tasiri daqiqlaçdirilmiçdir.

Açar sôzlsr: sistem, faza taraziligi, likvidus sathinin proyeksiyasi, xalkopirit fazasi, faza keçidi

ФАЗОВЫЕ РАВНОВЕСИЯ В КВАЗИТРОЙНОЙ СИСТЕМЕ Си1п8е2-ве-8е гН.М. Аллазова, 2Р.Ф. Аббасова, 2Т.М. Ильяслы, гИ.И. Алиев, 3М.Р. Аллазов

¡Институт Катализа и Неорганической Химии им.акад.М.Нагиева, Лг ¡¡43, Баку, пр. ГДжавида, ¡¡3 2Бакинский Государственный Университет.

Лг ¡¡48, Баку, ул.акад.З.Халилова, 23 3Азербайджанский Технический Университет Лг ¡073, Баку, пр. Г Джавида, 25 е-та11:а11агоу_т@та11.ги

Методами дифференциально-термического (ДТА), рентгенофазового (РФА), микроструктурного (МСА) и измерением микротвердости исследованы фазовые равновесия в тройной системе Си1п8е2-Ое-8е во всей концентрационной области. Результаты исследований обобщены и представлены в настоящей статье. Установлены фазовые диаграммы систем Си1пБе2- Ое, Си1п8е2-ОеБе, Си1пОеБе4 - Ое, Си1пОеБе4 - ОеБе, Си1пОеБе4 -8е, а также диаграммы проекции поверхности ликвидуса квазитройной системы. Определены моновариантные кривые, области расслаивания фаз в жидком состоянии, координаты монотектических, метатектических, перитектических и эвтектических процессов. Уточнены область первичной кристаллизации низкотемпературной полиморфной формы (фазы со структурой халькопирита) соединения Си1п8е2 в присутствие халькогенидов германия.

Ключевые слова: система, фазовые равновесия, проекция поверхности ликвидуса, халькопиритная фаза, фазовый переход.