Yup, a new material. Made with clay or clay and sand then baked in a kiln (or electrofurnace) to produce ceramic wafers. Perhaps it could also be cut to shape with a diamond tool of some sort, but useful in building specialized breeder reactors and components within them since ceramics are known to withstand immense amounts of heat. Ceramics are also nice for decorations, making mugs for drinking, etc. Stone mugs are nice, but ceramics can be painted with kittens and crap like that. And dyed, so your favorite coffee concoction can be enjoyed in a blue mug. Ceramics also make excellent tools for cutting, not so much for mining, but can be employed as a medium to hold cutting or grinding implements.
Ceramics are also excellent insulators for electrical purposes and are irreplacable in high powered circuits and switches as well as capacitor housings.
Ah yes, capacitors. Batteries from hell. That was the other suggestion. Still working on implementation of that, but ceramics would help regardless.