Processing of electric ceramic insulators from slate rocks and MgO

ABSTRACT

Ceramic bodies enriched with cordierite were successfully fabricated via solid state process using natural raw materials such as slate and kaolin, and their dielectric properties were investigated. Four batch compositions were designed, and partial substitution of MgO for slate was performed to increase the Mg content in the fabricated bodies and enhance the cordierite formation. The petrographic description, phase evolution, porosity, microstructure, mechanical properties and thermal expansion properties were systematically investigated. Different crystalline phases were present in the samples fired in the temperature range 1175–1250°C; the cordierite phase appeared in batch CS and was well crystallized in batch DS. As a result of the low porosity and existence of the mullite phase, sintered AS samples displayed the highest mechanical properties. The dielectric results indicated that the dielectric loss for the sintered bodies was within the range 10⁻²–10⁻³. A better loss tangent value was observed for batch DS. The tested samples were insulators, suggesting their potential use in microelectronic packaging and electro-ceramic protective coatings.

KEYWORDS:

• Cordierite
• slate
• magnesia
• fabrication
• ceramic
• microstructure
• sintering
• dielectric
• mechanical
• insulators