Ioplasma is made with tech level 7 or higher refineries. It is used to make Io Tubes, which are needed to make transporters and hull openings. Ioplasma is only found on worlds in the inferno zone. Not every inferno world will have ioplasma. Scan the planet before establishing a base to make sure it actually has ioplasma. It takes a very long time to "fetch" ioplasma from the atmosphere, so just be patient and wait for its production.