Fabrication of crack-free C12A7 nano-ceramics composite from eutectic glass in the C12A7-CaYAlO ₄ system

Crack formation in the C12A7 nano-composite during crystallization was successfully avoided by using the eutectic glass in the C12A7-CaYAlO ₄ system. The crystal phases from the eutectic glass were identified to be C12A7 (major phase) and CaYAlO ₄ (minor phase) by X-ray diffraction and high-resolution transmission electron microscope. It was indicated that origin of cracks upon crystallization of C12A7 glass was the volume expansion caused by crystallization of C12A7 in the glass and the cracking could be avoided by the volume shrinkage by crystallization of CaYAlO ₄ . By using a conventional molding technique, we have also succeeded to fabricate a bulk C12A7 composite with arbitrary shapes.