Characterization of 5 Different Clays Used in the Turkish Ceramic Industry and Determination of Their Mullite Formation Degrees

Abstract

In this study, chemical, mineralogical and technical properties of five different clay samples (Clay 1-2-3-4-5) that are widely used in the Turkish ceramic industry were investigated and correlations between raw material properties and the final performance of fired samples were presented. Comprehensive analytical methods such as XRD, XRF, TMA, DSC, and SEM were used to characterize the clays. The findings show that drying sensitivity and sintering behavior are strongly influenced by the mineralogical composition, namely the crystallinity of kaolinite and the presence of secondary phases such illite, quartz, and alkali oxides. Between 1100 and 1300°C, clays with high crystalline kaolinite (Clay 1 and Clay 2) developed more mullite and showed greater thermal stability. Furthermore, as the particle size distribution was the primary factor influencing the drying behavior, Clay-5, with the finest particles, was appointed as the highest drying sensitive sample. According to the study, raising the firing temperature improved flexural strength by boosting mullitization and liquid phase development while decreasing porosity and water absorption in all samples.

Keywords

• Clay
• clay minerals; Mullite
• XRD
• Rietveld refinement.

Türkiye Seramik endüstrsinde kullanılan 5 farklı kilin karakterizasyonu ve müllit oluşturma derecelerinin belirlenmesi

Abstract

Bu çalışmada, Türk seramik endüstrisinde yaygın olarak kullanılan beş farklı kil örneğinin (Kil 1-2-3-4-5) kimyasal, mineralojik ve teknik özellikleri araştırılmış ve hammadde özellikleri ile pişirilmiş örneklerin nihai performansı arasındaki ilişkiler ortaya konmuştur. Killeri karakterize etmek için XRD, XRF, TMA, DSC ve SEM gibi kapsamlı analitik yöntemler kullanılmıştır. Bulgular, kuruma duyarlılığı ve sinterleme davranışının, mineralojik bileşimden, özellikle kaolinitin kristalliğinden ve illit, kuvars ve alkali oksitler gibi ikincil fazların varlığından güçlü bir şekilde etkilendiğini göstermektedir. 1100 ve 1300°C arasında, yüksek kristalli kaolinit içeren kil (Kil 1 ve Kil 2) daha fazla müllit geliştirmiş ve daha yüksek termal stabilite göstermiştir. Ayrıca tane boyutu dağılımı kuruma davranışını etkileyen birincil faktör olduğundan, en ince tane yapısına sahip olan Kil-5, kuruma duyarlılığı en yüksek numune olarak belirlenmiştir. Çalışmaya göre, pişirme sıcaklığının yükseltilmesi, tüm numunelerde gözenekliliği ve su emilimini azaltırken, müllit oluşumu ve sıvı faz gelişimini artırarak eğme mukavemetini artırmaktadır.

Keywords

• Kil
• kil mineralleri
• müllit
• XRD
• Rietvel

References

1. [1] M. V. Vasic, O. Gencel, P. M. Velasco, “From raw clay to ceramics: Evaluating the suitability of raw materials through compositional analysis”, Boletin De La Sociedad Espanola De Ceramica y Vidrio, 64, 100455, 2025. doi.org/10.1016/j.bsecv.2025.100455
2. [2] C. Candeias, I. Santos, F. Rocha, “Characterization and Suitability for Ceramics Production of “Clays from Bustos, Portugal”, Minerals, 15, 503, 2025. doi.org/10.3390/min15050503
3. [3] W. M. Carty, U. Senapati, “Porcelain-Raw Materials, Processing, Phase Evolution, and Mechanical Behavior”, J. Am. Ceram. Soc., 81, [1], 3-20, 1998. doi/10.111/j.1151-2916.1998.tb02290.x
4. [4] A. Aras, “The change of phase composition in kaolinite- and illite-rich clay-based ceramic bodies”, Applied Clay Science, 24, 257-269, 2004. doi:10.1016/j.clay.2003.08.012
5. [5] M. Garcia-Valles, D. Cuevas, P. Alfonso, S. Martinez, “Thermal behaviour of ceramics obtained from the kaolinitic clays of Terra Alta, Catalonia, Spain”, Journal of Thermal Analysis and Calorimetry, 147:5303–5312, 2022. doi.org/10.1007/s10973-021-11075-9
6. [6] W.E. Lee, G.P. Souza, C.J. McConville, T. Tarvornpanich, Y. Iqbal, “Mullite formation in clays and clay-derived vitreous ceramics”, Journal of the European Ceramic Society, 28, 465-471, 2008. doi:10.1016/j.jeurceramsoc.2007.03.009
7. [7] O. Castelein, B, Soulestin, J.P. Bonnet, P. Blanchart, “The influence of heating rate on the thermal behaviour and mullite formation from a kaolin raw material”, Ceramics International, 27, 517-522, 2001.
8. [8] G. Yan, F. Wang, Y. Yang, J. Yang, R. He, Q. Gui, H. Zhou, J. Feng, “Controlling phase transfer of recycled coal-series kaolin waste used as superior admixture”, Results in Engineering, 29, 108683, 2026. doi.org/10.1016/j.rineng.2025.108683

9. [9] Y.F. Chen, M.C. Wang, M.H. Hon, “Phase transformation and growth of mullite in kaolin ceramics”, Journal of the European Ceramic Society, 24, 2389–2397, 2004. doi:10.1016/S0955-2219(03)00631-9.
10. [10] P. V. Lopez, M. F. Hernandez, D. Richard, M. S. Conconi, N. M. Rendtorff, “Porous acicular mullite ceramics produced from well and poorly crystallized kaolinite”, Applied Clay Science, 238, 106937, 2023. doi.org/10.1016/j.clay.2023.106937
11. [11] E. Escalera, R. Tegman, M.L. Antti, M. Oden, “High temperature phase evolution of Bolivian kaolinitic–illitic clays heated to 1250 °C”, Applied Clay Science, 101, 100-105, 2014. doi.org/10.1016/j.clay.2014.07.024.
12. [12] L. Andrini, M.R. Gauna, M.S. Conconi, G. Suarez, F.G. Requejo, E.F. Aglietti, N.M. Rendtorff, “Extended and local structural description of a kaolinitic clay, its fired ceramics and intermediates: An XRD and XANES analysis”, Applied Clay Science, 124-125, 39-45, 2016. doi.org/10.1016/j.clay.2016.01.049
13. [13] J. Li, Q. Liu, K. Li, Y. Li, N. Jiang, “Effect of MgO content on high-temperature phase transformation of kaolinitic coal gangue and on the production of cordierite”, Applied Clay Science, 279, 108030, 2026. doi.org/10.1016/j.clay.2025.108030
14. [14] G. Wallez, A. Bouquillon, Y. Coquinot, “Thermal evolution of a kaolin: Quantitative phase analysis and assessment of the thermal markers of the Provins clay”, Applied Clay Science, 261, 107582, 2024. doi.org/10.1016/j.clay.2024.107582
15. [15] H. Schneider, J. Schreuer, B. Hildmann, “Structure and properties of mullite-A review”, Journal of the European Ceramic Society 28, 329–344, 2008. doi:10.1016/j.jeurceramsoc.2007.03.017
16. [16] C.Y. Chen, G.S. Lan, W.H. Tuan, “Preparation of mullite by the reaction sintering of kaolinite and alumina”, Journal of the European Ceramic Society 20, 2519-2525, 2000.
17. [17] W.E. Lee, Y. Iqbal, “Influence of mixing on mullite formation in porcelain”, Journal of the European Ceramic Society, 21, 2583–2586, 2001.
18. [18] A. M. Segadaes, M. A. Carvalho, H. C. Ferreira, “Using phase diagrams to deal with moisture expansion”, Ceramics International, 29, 947–954, 2003. doi:10.1016/S0272-8842(03)00051-8
19. [19] J. M. R. de Figueiredo, J. R. S. Silva, D. de Araujo Neves, H. C. Ferreira, L. N. de Lima Santana, “Influence of Processing Variables on Clay-Based Ceramic Formulations”, Materials Research, 22(3) 2019. doi.org/10.1590/1980-5373-MR-2018-0548
20. [20] H. M. Zhou, X. C. Qiao, J. G. Yu, “Influences of quartz and muscovite on the formation of mullite from kaolinite”, Applied Clay Science, 80-81, 176-181, 2013. doi.org/10.1016/j.clay.2013.04.004