High-temperature impedance spectroscopy as a technique for monitoring the initial stages of phase transformations in minerals (exemplified by almandine from the Verkholovskaya garnet mine, Middle Urals)

   Research subject and Methods. The electrical characteristics of an almandine sample from the Verkholovskaya garnet mine (Middle Urals, Russia) were studied using high-temperature impedance spectroscopy in both heating and cooling modes, over a temperature range of 200–900 °С and a frequency range of 1–106 Hz. For this method, electrodes made of platinum and lanthanum-strontium cobaltite were employed. The results were interpreted in combination with thermogravimetric data, X-ray diffraction XRD analyses and diffuse light scattering measurements for almandine powders in their initial state, after annealing at 750 °С and for model synthetic iron oxide Fe₂O₃.

   Results. In the cooling mode, a linear dependence was observed with a break in the temperature range of 600–625 °С with characteristic activation energies E_a ^⬚ 0.58 and 0.81 eV in the low-temperature (200–625 °С) and high-temperature (625–900 °С) regions, respectively. During the heating-cooling cycle an anomaly was noted at 750 °С, where the sample’s resistance remained constant or changed insignificantly with increasing temperature. Analysis of impedance spectroscopy data revealed the onset of decomposition of the almandine sample already at 750 °С. Previously, no changes in phase composition had been reported at this temperature. The initial stage of almandine destruction is accompanied by the formation of nanosized particles of iron oxide Fe₂O₃ on its surface, which was confirmed by diffuse light scattering data. Traditional methods of detecting changes in phase composition (TG-DTA and X-ray phase analysis) indicate the appearance of the Fe₂O₃ phase only at temperatures above 750 °С. This may be associated with their insufficient sensitivity and/or the specific morphology of the released Fe₂O₃ phase.

   Conclusions. The impact of minor changes in the phase composition of compounds (initial stages of phase transformations) highlights the potential of impedance spectroscopy as a valuable tool for recording and investigating the early stages of thermal decomposition of both minerals and synthetic materials.

1. Aparicio C., Filip J., Skogby H., Marusak Z., Mashlan M., Zboril R. (2012) Thermal behavior of almandine at temperatures up to 1,200 °С in hydrogen. Phys. Chem. Minerals, 39, 311-318. doi: 10.1007/s00269-012-0488-x

2. Bakhterev V.V., Kuznetsov A. (2012) Zh. high-temperature conductivity of magnetite ores in relation to their genesis and mineral composition (by the example of the Goroblagodatskoe skarn-magnetite deposit). Geol. Geofiz., 53(2), 270-276. (In Russ.)

3. Barkova K., Mashlan M., Zboril R., Martinec P., Kula P. (2001) Thermal decomposition of almandine garnet: Mössbauer study. Czech. J. Phys., 51(7), 749-754. doi: 10.1023/A:1017618420189

4. Burns R.G. (1993) Mineralogical applications of crystal field theory (2^nd Ed). Cambridge: Cambridge University Press, 551 p. doi: 10.1017/CBO9780511524899

5. Dai L., Li H., Hu H., Jiang J., Hui K., Shan S. (2013) Electrical conductivity of Alm₈₂Py₁₅Grs₃ almandine-rich garnet determined by impedance spectroscopy at high temperatures and high pressures. Tectonophysics, 608, 1086-1093. doi: 10.1016/j.tecto.2013.07.004

6. Dai L., Hu H., Jiang J., Sun W., Li H., Wang M., Vallianatos F., Saltas V. (2020) An overview of the experimental studies on the electrical conductivity of major minerals in the upper mantle and transition zone. Materials, 13(2), 408. doi: 10.3390/ma13020408

7. Fullea J. (2017) On joint modelling of electrical conductivity and other geophysical and petrological observables to infer the structure of the lithosphere and underlying upper mantle. Surv. Geophys., 38, 963-1004. doi: 10.1007/s10712-017-9432-4

8. Gardner R.F.G., Sweett F., Tanner D.W. (1963). The electrical properties of alpha ferric oxide–I. J. Phys. Chem. Solids, 24(10), 1175-1181. doi: 10.1016/0022-3697(63)90234-8

9. Gavarri J. (1999) Transport properties and percolation in two-phase composites. Solid State Ion., 117(1-2), 75-85. doi: 10.1016/S0167-2738(98)00250-1

10. Gellings P.J. (2019) Handbook of solid state electrochemistry (1^st Ed). Boca Raton: CRC Press, 644 p.

11. Glover P.W.J. (2015) Geophysical properties of the near surface Earth: Electrical properties. Treat. Geophys. (2^nd Ed), 11. Amsterdam: Elsevier, 89-137. doi: 10.1016/B978-0-444-53802-4.00189-5

12. Huebner J.S., Dillenburg R.G. (1995) Impedance spectra of hot, dry, silicate minerals and rock: Qualitative interpretation of spectra. Amer. Miner., 80(1), 46-64. doi: 10.1016/10.2138/am-1995-1-206

13. Irvine J.T.S., Sinclair D.C., West A.R. (1990) Electroceramics: characterization by impedance spectroscopy. Adv. Mater., 2(3), 132-138. doi: 10.1002/adma.19900020304

14. Ivanova V.P., Kasatov B.K., Krasavina T.N., Rozinova E.L. (1974) Thermal analysis of minerals. Leningrad, Nedra, 399 p. (In Russ.)

15. Izawa M.R.M., Cloutis E.A., Rhind T., Mertzman S.A., Poitras J., Applin D.M. Mann P. (2018) Spectral reflectance (0.35–2.5 µm) properties of garnets: Implications for remote sensing detection and characterization. Icarus, 300, 392-410. doi: 10.1016/j.icarus.2017.09.005

16. Karato S., Duojun W. (2013) Electrical conductivity of minerals and rocks. Phys. Chem. Deep Earth. U. S.: John Wiley & Sons, 145-182.

17. Keppler H., McCammon C.A. (1996) Crystal field and charge transfer spectrum of (Mg, Fe)SiO₃ majorite. Phys. Chem. Minerals, 23, 94-98. doi: 10.1007/BF00202304

18. Ksenofontov D.A., Grebenev V.V., Zubkova N.V., Pekov I.V., Kabalov Yu.K., Chukanov N.V., Pushcharovsky D.Yu., Artamonova A.A. (2018) Catapleiite behavior under heating and crystal structure of the product of its high-temperature transformation – the new phase Na₆Zr₃[Si₉O₂₇] with nine-membered rings of Si-O-tetrahedra. Proc. Rus. Mineralog. Soc., 147(3), 94-108. (In Russ.) doi: 10.30695/zrmo/2018.1473.07

19. Kubelka P., Munk F. (1931) Ein Beitrag zur Optik derFarbanstriche. Z. Tech. Phys., 12, 593-601.

20. Lassoued A., Dkhil B., Gadri A., Ammar S. (2017) Control of the shape and size of iron oxide (α-Fe₂O₃) nanoparticles synthesized through the chemical precipitation method. Res. Phys., 7, 3007-3015. doi: 10.1016/j.rinp.2017.07.066

21. Lastovickova M. (1982) Temperature-time dependence of the electrical conductivity of garnets. Studia Geoph. et Geod., 26, 405-412. doi: 10.1016/B978-0-444-99662-6.50072-1

22. Makarova I.P., Grebenev V.V., Chernaya T.S., Verin I.A., Dolbinina V.V., Chernyshov D.Y., Koval’chuk M.V. (2013) Temperature-induced changes in the single-crystal structure of K₉H₇(SO₄)₈·H₂O. Crystallogr. Rep., 58(3), 393-400 (translated from Cristallografiya, 58(3), 380-387).

23. Manning P.G. (1967) The optical absorption spectra of some andradites and the identification of the ⁶A₁→⁴A₁ ⁴E(G) transition in octahedrally bonded Fe³⁺. Can. J. Earth Sci., 4(6), 1039-1047. doi: 10.1139/e67-070

24. Mizuno S., Yao H. (2021) On the electronic transitions of α-Fe₂O₃ hematite nanoparticles with different size and morphology: Analysis by simultaneous deconvolution of UV–vis absorption and MCD spectra. J. Magn. Magn. Mater., 517, 167389. doi: 10.1016/j.jmmm.2020.167389

25. Morales A.E., Mora E.S., Pal U. (2007) Use of diffuse reflectance spectroscopy for optical characterization of un-supported nanostructures. Rev. Mex. Fis., 53(5), 18-22.

26. Naif S., Selway K., Murphy B.S., Egbert G., Pommier A. (2021) Electrical conductivity of the lithosphere-asthenosphere system. Phys. Earth Planet. Int., 313, 106661. doi: 10.1016/j.pepi.2021.106661

27. Nan C.-W., Shen Y., Ma J. (2010) Physical Properties of Composites Near Percolation. Annu. Rev. Mater. Res., 40(1), 131-151. doi: 10.1146/annurev-matsci-070909-104529

28. Novikova N.E., Dudka A.P., Grossman V.G., Bazarov B.G., Verin I.A., Grebenev V.V., Stefanovich S.Yu., Bazarova Zh.G. (2018) Structure and phase transitions in Tl_4.86Fe_0.83Hf_1.17(MoO₄)₆ single crystals in the temperature range 85–800 K. III Baikal Materials Science Forum. Materials of the All-Russian scientific conference with international participation. Ulan-Ude, Buryat Scientific Center, SB RAS, 87-88. (In Russ.)

29. Oshchepkova A.V., Chubarov V.M., Bychinsky V.A., Kaneva E.V. (2020) Physicochemical simulation of the qualitative and quantitative phase composition of iron ores. J. Sib. Fed. Univ. Chem., 13(1), 65-77. (In Russ.) doi: 10.17516/1998-2836-0169

30. Parkhomenko E.I. (1965) Electrical properties of rocks. Moscow, Nauka, 164 p. (In Russ)

31. Parkhomenko E.I. (1984) Electrical properties of minerals and rocks at high pressures and temperatures. Diss. … Doctor of Physical and Mathematical Sciences. Moscow, Institute of Physics of the Earth named after. O.Yu. Schmidt, 420 p. (In Russ.)

32. Roberts J.J., Tyburczy J.A. (1993) Impedance spectroscopy of single and polycrystalline olivine: Evidence for grain boundary transport. Phys. Chem. Minerals, 20, 19-26. doi: 10.1007/BF00202246

33. Romano C., Poe B.T., Kreidie N., McCammon C.A. (2006) Electrical conductivities of pyrope-almandine garnets up to 19 GPa and 1700 °C. Amer. Miner., 91(8-9), 1371-1377. doi: 10.2138/am.2006.1983

34. Salikhov D.N., Belikova G.I., Sergeeva E.V. (2001) Thermodynamics of equilibrium of manganese ore minerals. Geological Collection, (2), 163-167. (In Russ.)

35. Sorokin N.I. (2009) Ionic conductivity of sodium silicates with lovozerite-type structure. Rus. J. Electrochem., 45(8), 946-948 (translated from Elektrokhimiya, 45(8), 1011-1013).

36. Sun W., Dai L., Li H., Hu H., Jiang J., Liu C. (2019) Experimental study on the electrical properties of carbonaceous slate: A special natural rock with unusually high conductivity at high temperatures and pressures. High Temperatures-High Pressures, 48, 439-454. doi: 10.32908/hthp.v48.749

37. Taran M.N., Dyar M.D., Matsyuk S.S. (2007) Optical absorption study of natural garnets of almandine-skiagite composition showing intervalence Fe²⁺ + Fe³⁺ → Fe³⁺ + Fesup>²⁺ charge-transfer transition. Amer. Miner., 92(5-6), 753-760. doi: 10.2138/am.2007.2163

38. Torrent J., Vidal B. (2002) Diffuse Reflectance Spectroscopy of Iron Oxides. Encyclopedia of surface and colloid science, 1. NY-Basel: Marcel Dekker Inc., 1438-1446.

39. Townsend T.K., Sabio E.M., Browning N.D., Osterloh F.E. (2011) Photocatalytic water oxidation with suspended alpha-Fe₂O₃ particles-effects of nanoscaling. Energy Environ. Sci., 4(10), 4270-4275. doi: 10.1039/C1EE02110A

40. Wheatstone C. (1843) XIII The Bakerian lecture. An account of several new instruments and processes for determining the constants of a voltaic circuit. Phil. Trans. R. Soc., 133, 303-327. doi: 10.1098/rstl.1843.0014

41. Yoshino T. (2019) Electrical properties of rocks. Encyclopedia of Solid Earth Geophysics. Cham: Springer, 1-7. doi: 10.1007/978-3-030-10475-7_45-1

42. Zhang L. (2017) A review of recent developments in the study of regional lithospheric electrical structure of the Asian continent. Surv. Geophys., 38, 1043-1096. doi: 10.1007/s10712-017-9424-4