Compressor Discharge Temperature
For comparison, P&WC PW150A (on Bombardier Q400) CDT is around 450 deg C (840 def F) at 250 PSIA. That's pretty hot for a 3-Stage Axial plus Single-stage Centrifugal compressor arrangement.
Slightly off-subject, I believe that if ceramic engine parts could be made at the same cost - or cheaper than the existing alloy parts, engine durability and longevity will benefit. Until then, the cost of manufacturing these parts will ensure the technology will remain stuck where it is. Several manufacturers have experimented with ceramic turbine blades with great success, but the cost made this option impossible.
Plastics / composites in turbine engine compressors? I doubt it, but I'm happy to stand corrected.