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ISSN 2522-1841 (Online) AZERBAIJAN CHEMICAL JOURNAL № 1 2021 43 ISSN 0005-2531 (Print) UDC546.56.86.22.15 PHYSICO-CHEMICAL INTERACTION OF THE COPPER AND ANTIMONY IODIDES P.R.Mammadli Azerbaijan State Oil and Industry University, Azerbaijani-French University M.Nagiev Institute of Catalysis and Inorganic Chemistry, NAS of Azerbaijan [email protected] Received 09.10.2020 Accepted 11.12.2020 The character of the mutual interaction of the components in the CuI–SbI3 system was studied by differ- ential thermal analysis and X-ray phase analysis methods and its phase diagram was constructed. It was found that the system is quasi-binary and forms a monotectic phase diagram. The immiscibility region covers ~15–93 mol% SbI3 concentration interval at the monotectic equilibrium temperature (~ 4930С). The temperatures of polymorphic transformations of the CuI compound in the system drop slightly and these phase transitions take place by metatectic reactions. Keywords: CuI–SbI3 system, fast-ion conductor, phase diagram, differential-thermal analysis, X-ray phase analysis. doi.org/10.32737/0005-2531-2021-1-43-47 Introduction ver, the formation of different ternary com- pounds has been reported in the AI–BV–I (AI – Metal halides are of potential interest due V to their application in semiconducting electronic Cu, Ag; B – As, Sb, Bi) type similar systems devices, nanotechnology, optoelectronics, ra- [1, 22–24]. In this regard, the present work is diation detectors, etc. [1–3]. devoted to the study of the physicochemical in- Copper (I) iodide CuI is earth-abundant teraction between the typical binary iodides of non-toxic material possessing stable p-type elec- the Cu–Sb–I system: CuI and SbI3. Primary compounds of the CuI–SbI sys- trical conductivity at room temperature and fast- 3 tem have been studied in detail. CuI melts at ionic conductivity at high temperatures [4–7]. It 6060C without decomposition. It has 3 modifica- has attracted much attention for its wide use as tions [25, 26]. The low-temperature γ-modifi- high-performance thermoelectric elements, trans- cation crystallizes in a surface-centered cubic parent electrodes for solar cells, flat-panel dis- lattice and transfers to the β-phase at 3690C. The plays, light-emitting diodes, etc. [8–13]. β-CuI phase crystallizes in a trigonal lattice, ex- Antimony triiodide SbI3 is a well-known ists in a small temperature range (~10K), and wide gap semiconductor, considered to be a po- transforms into the α phase at 4070C [25]. The tential material for radiation detectors [14], as latter phase also crystallizes in a cubic lattice 0 cathodes in solid-state batteries [15], in high-re- [26]. SbI3 melts at a low (172 C) temperature solution image micro recording and information [27] and crystallizes to the rhombohedral lattice storage [16]. Additionally, crystalline SbI3 exhib- with the space group 푅3̅ [28]. its the second-harmonic generation, which pro- vides a variety of opportunities for optoelectro- Experimental part nic devices [17, 18]. Antimony and iodine elementary compo- The search and design of new functional nents, as well as, CuI binary compound of the materials require investigation of the respective Alfa Aesar German brand (99.999 % purity) phase diagrams. Understanding the phase inter- were used in the course of experimental studies. SbI3 was prepared using elements of high action in the corresponding systems is always -2 helpful for the development of advanced mate- purity grade in an evacuated (~10 Pa) silica rials [19–21]. ampoule. Considering the high volatility of io- There is no literary information about the dine, the specially designed method was used for the synthesis of the SbI compound. The phase relations in the Cu–Sb–I system. Howe- 3 AZERBAIJAN CHEMICAL JOURNAL № 1 2021 44 P.R.MAMMADLI process was carried out in a 3-zone inclined It was established that the system is quasi- furnace. Temperatures of the 2 "hot" zones were binary and forms a phase diagram of a mono- kept at 470K and 750K, whereas the tempera- tectic type. Monotectic equilibrium / ture of the "cold" zone was 400 K (the sublima- L1(m) ↔ L2(m ) + (HT2-CuI) tion temperature of iodine is 386 K). After the is observed at 4930C temperature. The immisci- main portion of iodine reacted at 470K, the am- bility region at 4930C ranges at the 15–93 mol% poule inserted into the second hot zone where SbI3 concentration interval. the product melted at 750K. After stirring the DTA results of the CuI-SbI3 system homogeneous liquid at this temperature the fur- 0 Composition, mol% SbI3 Thermal effects, C nace cooled gradually. The purity and individu- 0 (pure CuI) 369; 407; 606 ality of the obtained product were monitored 5 167; 367; 391; 493; 493–567 using differential thermal analysis (DTA) and 10 168; 367; 391; 494; 494–525 X-ray phase analysis (XRD) methods. 15 168; 366; 392; 492 Two sets of samples (0.5 g each) of the 20 168; 366; 390; 492 30 168; 368; 392; 494 CuI-SbI3 system were prepared by сo-melting of different proportions of the CuI and pre- 40 168; 367; 390; 493 50 167; 387; 391; 494 prepared SbI3 compounds in quartz ampoules. 60 167; 367; 390; 493 Thermal annealing of samples was carried out 70 168; 367; 392; 493 at ~400K (~20–30K below the solidus tem- 80 168; 366; 391; 494 perature) for 1000 hours in order to achieve 90 169; 367; 391; 492 complete homogenization. 95 167; 167–450 Experimental studies were conducted by 100 (pure SbI3) 170 using DTA and XRD methods. The DTA was A slight decrease in the phase transition carried out using the differential-scanning calo- temperatures of the CuI compound in the sys- rimeter "NETZSCH 404 F1 Pegasus system" tem indicates the existence of solubility areas (heating speed of 10 K/min), and XRD – by based on its HT1 and HT2 modifications, and means of the Bruker D8 diffractometer (CuKα that the phase transitions occur by metatectic 0 0 radiation) at 2θ =5 –75 . reactions. Experimental results and discussion Isotherms corresponding to the tempera- tures 391 and 3670C on the phase diagram, re- The powder X-ray diffraction patterns of spectively reflect the thermally treated CuI-SbI3 alloys are given in (HT2-CuI) ↔ L2 + (HT1-CuI) and Figure 1. As can be seen, the diffraction patterns (HT1-CuI) ↔ L2 + LT-CuI of samples in the full composition range consist metatectic equilibria. of the diffraction peaks of the low-temperature modification of CuI and SbI3. Diffraction lines of Eutectic has a ~97 mol% SbI3 composi- 0 the alloys do not displace relative to the pure tion and melts at 167 C by the reaction: components (Figure 1). It proves that there are L → LT-CuI + SbI3 no solid solution areas based on the initial com- As mentioned before, there is practically no pounds of the system. This can be explained by solubility in the solid state between the low- the fact that the nature of the chemical bond in temperature modification of CuI and SbI3. these substances is very different. The Tamman triangle, constructed based on the The T–x phase diagram of the system intensities of the thermal effects related to mon- (Figure 2) was constructed using DTA results otectic equilibrium, made it possible to deter- (Table). Here, the symbols HT2, HT1, and LT mine the presence of up to ~ 3 mol% solubility indicate high, intermediate, and low-temperature based on the (HT2-CuI), as well as to define the modifications of CuI, respectively. Solid solu- mutually saturated compositions of the L1 and tions based on them are indicated in the bracket. L2 immiscible liquids. AZERBAIJAN CHEMICAL JOURNAL № 1 2021 PHYSICO-CHEMICAL INTERACTION OF THE COPPER AND….. 45 Fig. 1. X-ray images of different alloys of the CuI-SbI3 system: 1 – SbI3, 2 – 90 mol.% SbI3, 3 – 80 mol.% SbI3, 4 – 60 mol.% SbI3, 5 – 50 mol.% SbI3, 6 – 40 mol.% SbI3, 7 – 20 mol.% SbI3, 8 – 10 mol.% SbI3, 9 – CuI. Fig. 2. T–x phase diagram of the CuI–SbI system. 3 AZERBAIJAN CHEMICAL JOURNAL № 1 2021 46 P.R.MAMMADLI Conclusion 11. Wang P., Zhang J., Zeng Z., Chen R., Huang X., Wang L., Xu J., Hu Z., Zhu Y. Copper iodide as a For the first time, the nature of the physi- potential low-cost dopant for spiro-MeOTAD in cochemical interaction of copper and antimony perovskite solar cells. J. Mater. Chem. C. 2016. V. iodides was determined by DTA and X-ray 4. No 38. P. 9003-9008. methods. It is shown that, in contrast to similar 12. Christians J.A., Fung R.C.M., Kamat P.V. An In- systems consisting of copper and silver halides, organic Hole Conductor for Organo-Lead Halide Perovskite Solar Cells. Improved Hole Conduc- ternary compounds are not formed in the CuI- tivity with Copper Iodide. J. Am. Chem. Soc. SbI3 system. There is a wide immiscibility area 2014. V. 136. No 2. P. 758–764. in the system. Phase transitions of copper (I) 13. Mohamed S.A., Gasiorowski J., Hingerl K., Zahn iodide occur by metatectic reactions. D.R.T., Scharber M.C., Obayya S.S.A., El-Mansy M.K., Sariciftci N.S., Egbe D.A.M., Stadler P. CuI References as versatile hole-selective contact for organic solar cell based on anthracene-containing PPE–PPV. 1. Ivanov-Shchitc A.K., Moorein I.V. Ionika tver- Sol. Energy Mater. Sol. Cells. 2015. V. 143. P. dogo tela. V 2-kh tomakh. T. 1. SPb.: Izd-vo S.- 369–374. Peterb. un-ta. 2000. 616 s. 14. Onodera T., Baba K., Hitomi K. Evaluation of An- 2.