Effect of cristobalite on the response to indentation in potassium-fluorrichterite glass-ceramics

Keitaro HIRAOKA; Gaku Okuma; Akihisa TAKEUCHI; Masayuki UESUGI; Yuki SADA; Ken-ichi KATSUMATA; Atsuo YASUMORI; Kei MAEDA

doi:10.2109/jcersj2.25077

Journal article Effect of cristobalite on the response to indentation in potassium-fluorrichterite glass-ceramics

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Keitaro HIRAOKA, Gaku Okuma, Akihisa TAKEUCHI, Masayuki UESUGI, Yuki SADA, Ken-ichi KATSUMATA, Atsuo YASUMORI, Kei MAEDA. Effect of cristobalite on the response to indentation in potassium-fluorrichterite glass-ceramics. Journal of the Ceramic Society of Japan. 2025, 133 (11), 703-708. https://doi.org/10.2109/jcersj2.25077

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Glass-ceramics containing potassium-fluorrichterite (KNaCaMg5Si8O22F2) as the primary crystalline phase are known for their high bending strength and fracture toughness. It is also recognized that cristobalite precipitates in the commercial product as a secondary phase. This study investigated the response to indentation to identify the effect of cristobalite in potassium-fluorrichterite glass-ceramics with a chemical composition similar to that of the commercial product. The results revealed that the addition of 0.79 wt% Li2O promoted the precipitation of cristobalite during heat treatment at temperatures up to 1000 °C. A distinct volume change associated with the α–β phase transition of cristobalite was observed at approximately 200 °C. Vickers indentation tests indicated that hardness decreased with the growth of potassium-fluorrichterite crystals and further declined with the precipitation of cristobalite. The glass-ceramics containing both potassium-fluorrichterite and cristobalite exhibited permanent, hemispherical surface deformation in ball indentation tests. Synchrotron radiation X-ray computed tomography revealed the formation of microcracks in the cristobalite-containing glass-ceramics. It was suggested that the microcracks generated by stresses arising from the cristobalite phase transition led to the deformation and consequently contributed to the ductile behavior of the material. The findings of this study are expected to provide valuable insights into the microstructural design of cristobalite-containing glass-ceramics with enhanced mechanical performance.

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