Skip to main content

Solution Precursor Plasma Spraying of Cr-Doped Al2O3 Thermochromic Coatings


Solution precursor plasma spraying (SPPS) presents a modern route to deposit coatings directly from liquid feedstock. In this study, unique ability of SPPS to intermix different precursors on the atomic scale was employed to deposit pure and Cr-doped Al2O3 (technically, synthetic ruby) from several mixtures of aluminum and chromium nitrates. Highly porous coatings (> 60% porosity) were deposited by high-enthalpy WSP-H torch. Homogeneous distribution of Cr atoms in Al2O3 resulted in coatings color ranging from pink to grayish-green correlated with increasing Cr content and change of lattice parameters as observed by x-ray diffraction. High content of over 80 wt.% of α-alumina phase was reached for all coatings. For the Cr-doped Al2O3 coatings, distinct and fully reversible thermochromic behavior was observed by temperature-resolved colorimetry. Further increase in α-phase content (up to 95 wt.%) and coating densification were achieved by additional surface remelting by plasma torch.

This is a preview of subscription content, access via your institution.

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


  1. 1.

    X. Ma and P. Ruggiero, Practical Aspects of Suspension Plasma Spray for Thermal Barrier Coatings on Potential Gas Turbine Components, J. Therm. Spray Technol., 2018, 27(4), p 1-12

    Article  Google Scholar 

  2. 2.

    J. Smith, N. Shores, J. Scheibel, D. Classen, S. Paschke, S. Elbel, K. Fick, and D. Carlson, Thermal Barrier Coating Validation Testing for Industrial Gas Turbine Combustion Hardware, J. Eng. Gas Turbine Power, 2016, 138(March), p 1-7

    Google Scholar 

  3. 3.

    G. Darut, F. Ben-Ettouil, A. Denoirjean, G. Montavon, H. Ageorges, and P. Fauchais, Dry Sliding Behavior of Sub-Micrometer-Sized Suspension Plasma Sprayed Ceramic Oxide Coatings, J. Therm. Spray Technol., 2010, 19(1-2), p 275-285

    CAS  Article  Google Scholar 

  4. 4.

    T.P.S. Sarao, H. Singh, and H. Singh, Enhancing Biocompatibility and Corrosion Resistance of Ti-6Al-4V Alloy by Surface Modification Route, J. Therm. Spray Technol., 2018, 27(8), p 1388-1400.

    Article  Google Scholar 

  5. 5.

    J. Cizek, V. Brozek, T. Chraska, F. Lukac, J. Medricky, R. Musalek, T. Tesar, F. Siska, Z. Antos, J. Cupera, M. Matejkova, Z. Spotz, S. Houdkova, and M. Kverka, Silver-Doped Hydroxyapatite Coatings Deposited by Suspension Plasma Spraying, J. Therm. Spray Technol., 2018, 27(8), p 1333-1343.

    CAS  Article  Google Scholar 

  6. 6.

    P.L. Fauchais, J.V.R. Heberlein, and M.I. Boulos, Thermal Spray Fundamentals, Springer, Berlin, 2014,

    Book  Google Scholar 

  7. 7.

    N. Curry, K. VanEvery, T. Snyder, and N. Markocsan, Thermal Conductivity Analysis and Lifetime Testing of Suspension Plasma-Sprayed Thermal Barrier Coatings, Coatings, 2014, 4(3), p 630-650.

    CAS  Article  Google Scholar 

  8. 8.

    M. Gell, L. Xie, E.H. Jordan, and N.P. Padture, Mechanisms of Spallation of Solution Precursor Plasma Spray Thermal Barrier Coatings, Surf. Coat. Technol., 2004, 188-189(1-3 SPEC.ISS.), p 101-106

    CAS  Article  Google Scholar 

  9. 9.

    V.E. Oliker, A.E. Terent’Ev, L.K. Shvedova, and I.S. Martsenyuk, Use of Aqueous Suspensions in Plasma Spraying of Alumina Coatings, Powder Metall. Met. Ceram., 2009, 48(1-2), p 115-120

    CAS  Article  Google Scholar 

  10. 10.

    K. VanEvery, M.J.M. Krane, R.W. Trice, H. Wang, W. Porter, M. Besser, D. Sordelet, J. Ilavsky, and J. Almer, Column Formation in Suspension Plasma-Sprayed Coatings and Resultant Thermal Properties, J. Therm. Spray Technol., 2011, 20, p 817-828

    CAS  Article  Google Scholar 

  11. 11.

    E.H. Jordan, C. Jiang, and M. Gell, The Solution Precursor Plasma Spray (SPPS) Process: A Review with Energy Considerations, J. Therm. Spray Technol., 2015, 24(7), p 1153-1165.

    CAS  Article  Google Scholar 

  12. 12.

    W.H. Gitzen, Ed., Alumina as a Ceramic Material, American Ceramic Society, Columbus, 1970

    Google Scholar 

  13. 13.

    P. Chraska, J. Dubsky, K. Neufuss, and J. Pisacka, Alumina-Base Plasma-Sprayed Materials Part I: Phase Stability of Alumina and Alumina-Chromia, J. Therm. Spray Technol., 1997, 6, p 320-326

    CAS  Article  Google Scholar 

  14. 14.

    J. Dubsky, P. Chraska, B. Kolman, C.C. Stahr, and L.-M. Berger, Phase Formation Control in Plasma Sprayed Alumina-Chromia Coatings, Ceram. Silikáty, 2011, 55(3), p 294-300

    CAS  Google Scholar 

  15. 15.

    C.C. Stahr, S. Saaro, L.M. Berger, J. Dubský, K. Neufuss, and M. Herrmann, Dependence of the Stabilization of α-Alumina on the Spray Process, J. Therm. Spray Technol., 2007, 16, p 822-830

    CAS  Article  Google Scholar 

  16. 16.

    K. Yang, X. Zhou, H. Zhao, and S. Tao, Microstructure and Mechanical Properties of Al2O3–Cr2O3 Composite Coatings Produced by Atmospheric Plasma Spraying, Surf. Coat. Technol., 2011, 206(6), p 1362-1371.

    CAS  Article  Google Scholar 

  17. 17.

    J.R. Davis, Ed., Handbook of Thermal Spray Technology, ASM International, Materials Park, 2004

    Google Scholar 

  18. 18.

    T. Tesar, R. Musalek, F. Lukac, J. Medricky, J. Cizek, V. Rimal, S. Joshi, and T. Chraska, Increasing α-Phase Content of Alumina-Chromia Coatings Deposited by Suspension Plasma Spraying Using Hybrid and Intermixed Concepts, Surf. Coat. Technol., 2019, 2018, p 1-14.

    CAS  Article  Google Scholar 

  19. 19.

    S. Björklund, S. Goel, and S. Joshi, Function-Dependent Coating Architectures by Hybrid Powder-Suspension Plasma Spraying: Injector Design, Processing and Concept Validation, Mater. Des., 2018, 142(1), p 56-65.

    Article  Google Scholar 

  20. 20.

    S.V. Joshi, G. Sivakumar, T. Raghuveer, and R.O. Dusane, Hybrid Plasma-Sprayed Thermal Barrier Coatings Using Powder and Solution Precursor Feedstock, J. Therm. Spray Technol., 2014, 23(4), p 616-624

    CAS  Article  Google Scholar 

  21. 21.

    A. Potthoff, R. Kratzsch, M. Barbosa, and N. Kulissa, Development and Application of Binary Suspensions in the Ternary System Cr2O3-TiO2-Al2O3 for S-HVOF Spraying, J. Therm. Spray Technol., 2018, 27(4), p 710-717.

    CAS  Article  Google Scholar 

  22. 22.

    G. Sivakumar, R.O. Dusane, and S.V. Joshi, A Novel Approach to Process Phase Pure α-Al2O3 Coatings by Solution Precursor Plasma Spraying, J. Eur. Ceram. Soc., 2013, 33(13-14), p 2823-2829.

    CAS  Article  Google Scholar 

  23. 23.

    G. Sivakumar, M. Ramakrishna, R.O. Dusane, and S.V. Joshi, Effect of SPPS Process Parameters on In-Flight Particle Generation and Splat Formation to Achieve Pure α-Al2O3 Coatings, J. Therm. Spray Technol., 2015, 24(7), p 1221-1234.

    CAS  Article  Google Scholar 

  24. 24.

    T. Tesar, R. Musalek, J. Medricky, J. Kotlan, F. Lukac, Z. Pala, P. Ctibor, T. Chraska, S. Houdkova, V. Rimal, and N. Curry, Development of Suspension Plasma Sprayed Alumina Coatings with High Enthalpy Plasma Torch, Surf. Coat. Technol., 2017, 325(25), p 277-288.

    CAS  Article  Google Scholar 

  25. 25.

    M.I.B. Bernardi, S.C.L. Crispim, A.P. Maciel, A.G. Souza, M.M. Conceição, E.R. Leite, and E. Longo, Synthesis and Characterization of Al2O3/Cr2O3-Based Ceramic Pigments, J. Therm. Anal. Calorim., 2004, 75(2), p 475-480

    CAS  Article  Google Scholar 

  26. 26.

    H.-J. Lunk, Discovery, Properties and Applications of Chromium and Its Compounds, ChemTexts, 2015, 1(1), p 6.

    CAS  Article  Google Scholar 

  27. 27.

    B.D. Fahlman and A.R. Barron, CVD of Chromium-Doped Alumina “Ruby” Thin Films, Chem. Vap. Depos., 2001, 7(2), p 62-66

    CAS  Article  Google Scholar 

  28. 28.

    G. Salek, A. Devoti, E. Lataste, A. Demourgues, A. Garcia, V. Jubera, and M. Gaudon, Optical Properties versus Temperature of Cr-Doped γ-and α-Al2O3: Irreversible Thermal Sensors Application, J. Lumin., 2016, 179(3), p 189-196.

    CAS  Article  Google Scholar 

  29. 29.

    D.K. Nguyen, H. Lee, and I.T. Kim, Synthesis and Thermochromic Properties of Cr-Doped Al2O3 for a Reversible Thermochromic Sensor, Materials (Basel), 2017, 10(5), p 476-489

    Article  Google Scholar 

  30. 30.

    K. Nassau, The Physics and Chemistry of Color: The 15 Mechanisms, The Science of Color, 2nd ed., S.K. Shevell, Ed., Elsevier, Amsterdam, 2003, p 247-280

    Chapter  Google Scholar 

  31. 31.

    S.W.S. McKeever, Thermoluminescence of Solids, Cambridge University Press, Cambridge, 1988

    Google Scholar 

  32. 32.

    D. Liu, Effects of Cr Content and Morphology on the Luminescence Properties of the Cr-Doped Alpha-Al2O3 Powders, Ceram. Int., 2013, 39(5), p 4765-4769.

    CAS  Article  Google Scholar 

  33. 33.

    M. Hrabovsky, V. Kopecky, V. Sember, T. Kavka, O. Chumak, and M. Konrad, Properties of Hybrid Water/Gas DC Arc Plasma Torch, IEEE Trans. Plasma Sci., 2006, 34(4), p 1566-1575.

    Article  Google Scholar 

  34. 34.

    R. Musalek, J. Medricky, T. Tesar, J. Kotlan, Z. Pala, F. Lukac, K. Illkova, M. Hlina, T. Chraska, P. Sokolowski, and N. Curry, Controlling Microstructure of Yttria-Stabilized Zirconia Prepared from Suspensions and Solutions by Plasma Spraying with High Feed Rates, J. Therm. Spray Technol., 2017, 26(8), p 1787-1803

    CAS  Article  Google Scholar 

  35. 35.

    O. Panák, M. Držková, N. Kailová, and T. Syrový, Colorimetric Analysis of Thermochromic Samples in Different Forms Employing a Digital Camera, Meas. J. Int. Meas. Confed., 2018, 127, p 554-564

    Article  Google Scholar 

  36. 36.

    O. Panák, M. Držková, and M. Kaplanová, Insight into the Evaluation of Colour Changes of Leuco Dye Based Thermochromic Systems as a Function of Temperature, Dye. Pigment., 2015, 120, p 279-287

    Article  Google Scholar 

  37. 37.

    A.V. Belykh, A.M. Efremov, and M.D. Mikhailov, Thermochromic Material, European Patent Office, 2012, p 13.

  38. 38.

    D. Chen, E.H. Jordan, and M. Gell, The Solution Precursor Plasma Spray Coatings: Influence of Solvent Type, Plasma Chem. Plasma Process., 2010, 30(1), p 111-119

    Article  Google Scholar 

  39. 39.

    A. Joulia, G. Bolelli, E. Gualtieri, L. Lusvarghi, S. Valeri, M. Vardelle, S. Rossignol, and A. Vardelle, Comparing the Deposition Mechanisms in Suspension Plasma Spray (SPS) and Solution Precursor Plasma Spray (SPPS) Deposition of Yttria-Stabilised Zirconia (YSZ), J. Eur. Ceram. Soc., 2014, 34(15), p 3925-3940.

    CAS  Article  Google Scholar 

  40. 40.

    D. Triantafyllidis, L. Li, and F.H. Stott, Crack-Free Densification of Ceramics by Laser Surface Treatment, Surf. Coat. Technol., 2006, 201(6), p 3163-3173

    CAS  Article  Google Scholar 

  41. 41.

    P. Ballirano and R. Caminiti, Rietveld Refinements on Laboratory Energy Dispersive X-Ray Diffraction (EDXD) Data, J. Appl. Crystallogr., 2001, 34(6), p 757-762.

    CAS  Article  Google Scholar 

  42. 42.

    I.F. Myronyuk, V.I. Mandzyuk, V.M. Sachko, and V.M. Gunko, Structural and Morphological Features of Disperse Alumina Synthesized Using Aluminum Nitrate Nonahydrate, Nanoscale Res. Lett., 2016, 11(1), p 153.

    CAS  Article  Google Scholar 

  43. 43.

    H. Sawada, Residual Electron Density Study of Chromium Sesquioxide by Crystal Structure and Scattering Factor Refinement, Mater. Res. Bull., 1994, 29(3), p 239-245

    CAS  Article  Google Scholar 

  44. 44.

    E. Turunen, T. Varis, T.E. Gustafsson, J. Keskinen, T. Fält, and S.P. Hannula, Parameter Optimization of HVOF Sprayed Nanostructured Alumina and Alumina-Nickel Composite Coatings, Surf. Coat. Technol., 2006, 200(16-17), p 4987-4994

    CAS  Article  Google Scholar 

  45. 45.

    P.P. Psyllaki, M. Jeandin, and D.I. Pantelis, Microstructure and Wear Mechanisms of Thermal-Sprayed Alumina Coatings, Mater. Lett., 2001, 47(1-2), p 77-82

    CAS  Article  Google Scholar 

  46. 46.

    Y. Gao, X. Xu, Z. Yan, and G. Xin, High Hardness Alumina Coatings Prepared by Low Power Plasma Spraying, Surf. Coat. Technol., 2002, 154(2-3), p 189-193

    CAS  Article  Google Scholar 

  47. 47.

    R.G. Burns, Mineralogical Applications of Crystal Field Theory, 2nd ed., Cambridge University Press, Cambridge, 1993

    Book  Google Scholar 

  48. 48.

    J. Medricky, R. Musalek, M. Janata, T. Chraska, and F. Lukac, Cost-Effective Plasma Spraying for Large-Scale Applications, ITSC 2018—Proceedings of the International Thermal Spray Conference, F. Azarmi, K. Balani, T. Eden, T. Hussain, Y.-C. Lau, H. Li, K. Shinoda, F.-L. Toma, and J. Veilleux, Ed., Orlando, ASM International, 2018, p 683-689

    Google Scholar 

  49. 49.

    C. Lempereur, R. Andral, and J.Y. Prudhomme, Surface Temperature Measurement on Engine Components by Means of Irreversible Thermal Coatings, Meas. Sci. Technol., 2008, 19(10), p 105501

    Article  Google Scholar 

Download references


Financial support of the 19-10246S grant “Deposition mechanisms and properties of multiphase plasma-sprayed coatings prepared with liquid feedstocks” funded by Czech Science Foundation is gratefully acknowledged.

Author information



Corresponding author

Correspondence to Tomas Tesar.

Additional information

Publisher's Note

Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.

Rights and permissions

Reprints and Permissions

About this article

Verify currency and authenticity via CrossMark

Cite this article

Tesar, T., Musalek, R., Lukac, F. et al. Solution Precursor Plasma Spraying of Cr-Doped Al2O3 Thermochromic Coatings. J Therm Spray Tech 29, 199–211 (2020).

Download citation


  • Alumina
  • hybrid plasma torch
  • mixtures
  • oxides
  • phase composition
  • solution precursor spraying