Zirconium nitrate of chemical suppliers. It is used as a source of zirconium for other salts, as an analytical standard, or as a preservative. Zirconium nitrate and nitronium pentanitratozirconate can be used as chemical vapour deposition precursors as they are volatile, and decompose above 100 °C to form zirconia. At 95°C zirconium nitrate sublimes with a pressure of 0.2 mm of Hg and can be deposited as zirconium dioxide on silicon at 285°C. It has the advantage in that it is a single source, meaning it does not have to be mixed with other materials like oxygen, and decomposes at a relatively
Synthetic element of the Earth. Only minute traces of technetium occur naturally in the Earth's crust—as a spontaneous fission product of uranium-238 or by neutron capture in molybdenum ores—but technetium is present naturally in red giant stars. The first discovered purely synthetic element was curium, synthesized in 1944 by Glenn T. Seaborg, Ralph A. James, and Albert Ghiorso by bombarding plutonium with alpha particles. The discoveries of americium, berkelium, and californium followed soon. Einsteinium and fermium were discovered by a team of scientists led by Albert Ghiorso in 1952 while studying the radioactive debris from the detonation of the first hydrogen bomb.