On scorched, be sure you have full ghillie(heat) and a jerboa(super easy tame) to notify you of weather events. Phoenix only comes during heat wave so listen for “high pitch purr” from your jerboa. Search the map and find this awesome bird! Once that’s done just wait and see where it despawns when heat wave is over. You will see a glowing light on the ground. BUILD A PEN AT LEAST 6 WALLS HIGH AND 6 WALLS WIDE AROUND THAT SPOT. Reason is it tends to respawn above the ground since it never lands. Next heat wave, pray your calculations are correct and it’s trapped! After that just use a flame thrower OR fire wyvern to burn the Phoenix for tame. Again, this thing only spawns during heat waves so be efficient!
You can get it to spawn next to your base because of the following: It always respawns at it's last location, so if the heatwave ends while you are following it you will know where it is for the next heatwave. It also chases you when you eat flowers... hint hint
Find a phenix during a heatwave and follow it until it ends. The phenix will turn into ashes and land on the ground but will spawn right back at the same exact spot during the next heatwave. Build a trap 6 blocks high so I can't glitch out and you have yourself a trapped phenix to tame:)