Strontium titanate

Strontium titanate is an ceramics.

The name tausonite was given in honour of Lev Vladimirovich Tauson (1917-1989), a Russian geochemist. Disused trade names for the synthetic product include strontium mesotitanate, Fabulite, Diagem, and Marvelite.

Other than its type locality of the Murun Massif in the Sakha Republic, natural tausonite is also found in Cerro Sarambi, Concepción department, Paraguay; and along the Kotaki River of Honshū, Japan.

Properties

Strontium titanate is both much denser (specific gravity 4.88 for natural, 5.13 for synthetic) and much softer (sodium light, 589.3 nm) is nearly identical to that of diamond, but the dispersion (the optical property responsible for the "fire" of the cut stones) of strontium titanate is over four times higher, at 0.19 (B–G interval). This results in an excess of fire when compared to diamond.

Synthetics are usually transparent and colourless, but can be hydrofluoric acid.

Synthetic material has a very large superconductive properties.

At temperatures lower than 105 K, its cubic structure transforms to sputter deposition targets.

Nb:SrTiO₃, niobium doped strontium titanate, is electrically conductive.

Synthesis

Synthetic strontium titanate was one of several titanates patented during the late 1940s and early 1950s; other titanates included barium titanate and calcium titanate. Research was conducted primarily at the National Lead Company (later renamed N. L. Industries, Inc.) in the United States, by Leon Merker and Langtry E. Lynd. Merker and Lynd first patented the growth process on February 10, 1953; a number of refinements were subsequently patented over the next four years, such as modifications to the feed powder and additions of colouring dopants.

A modification to the basic chloride, heated to 1000°C in order to produce a free-flowing granular powder of the required composition, and is then ground and sieved to ensure all particles are between 0.2–0.5 micrometres in size.

The feed powder falls through the oxyhydrogen flame, melts, and lands on a rotating and slowly descending pedestal below. The height of the pedestal is constantly adjusted to keep its top at the optimal position below the flame, and over a number of hours the molten powder cools and crystallises to form a single pedunculated pear or annealing in an oxidizing atmosphere in order to make the crystal colourless and to relieve strain. This is done at over 1000°C for 12 hours.