Hydride films display mirror-window changes

Dutch researchers have achieved "spectacular changes" in optical properties of hydride films—switching them between a reflective, mirrorlike state and a transparent, windowlike state. The room-temperature, completely reversible process may find wide application in such fields as architecture, optical communication, laser technology, and even photography. Scientists at the Condensed Matter Physics & Spectroscopy (COMPAS) Institute at Vrije University in Amsterdam exposed thin films of yttrium and lanthanum hydrides to hydrogen atmospheres. They found that mirrorlike dihydride films coated with protective layers of palladium absorb hydrogen to form transparent, windowlike films of the corresponding trihydrides [Nature , 380, 231 (1996)]. The discovery was "a rather unexpected spin-off' of a research project on hydrogen metallization funded by the Foundation for Fundamental Research on Matter, in Utrecht, notes team leader Ronald Griessen, who is COMPAS's scientific director. "The first observation of optica...