Normally, when you think of PEEK in 3D printing, you think of a part made of PEEK, suitable for lower-temperature plastics. [ND-3D] has a different idea: printing with PEEK. You can get the details over on Hackaday.io, and there are a few YouTube videos below. Using a special controller and a halogen lamp, you can modify your own printer to use this exotic material often found in printer hot ends.
Logically, if PEEK is used near the hot end of regular printers, it must need a higher temperature to print. PEEK has a glass transition temperature of about 143 °C and melts at 343 °C. Compare this to PLA, which melts between 150 °C and 180 °C and has a glass transition temperature of only 60 °C.