why is the compressive strength of ceramics higher than other materials?
The strength of ceramics in general is higher than in other materials. The reason for high strength in ceramics is related to the predominantly ionic nature of the bonding that is characteristic of most ceramics. Ionic structures (vs. metallic crystals) are extremely resistant to the motion of dislocations in the lattice. Dislocations are the microscopic mechanism by which a material is able to plastically deform, and yield. Thus, metals, which allow relatively free dislocation motion yield and deform more easily than ceramics. This makes them less strong, and more ductile. Now in terms of compressive vs. tensile, the reason ceramics are quoted in textbooks as having much higher compressive strengths than tensile strengths is because it is nearly impossible to process bulk ceramics without internal flaws such as vacancies, or pores, which act as stess concentrations, and crack starters. Since ceramics are brittle, they are very sensitive to these internal flaws. This is why ceramics are typically described as Strong and brittle, and metals are described as Weaker and ductile There is lots of research that shows if you make a ceramic fiber of small enough diamter (micron scale) , you can eliminate the internal flaws, and achieve tensile strengths comparable to those observed in compression.
Tensile Strength Of Ceramics
