Perhaps you should try some spelling variations:
critical materials » chemical materials, artificial materials, frictional materials
organic materials » ceramic materials
optic materials » ionic materials, plastic materials, elastic materials
basic materials » basic material, plastic materials, elastic materials

You may be able to get more results by adjusting your search query.

• If you are trying to use Boolean operators, they must be ALL CAPS: %((((optical materials) OR (((((optic materials) OR (basic materials))) OR (organic materials))))) OR (critical materials))%22.
• Adding a wildcard symbol may retrieve word variants: %((((optical materials) or (((((optic materials) or (basic materials))) or (organic materials))))) or (critical materials))%22*.