Lanthanum decahydride

Among the “holy grails” in chemistry and physics is the development of practical superconductive materials. A substance is a superconductor if it exhibits no electrical resistance when it is cooled to below a certain temperature, called the critical transition temperature or T_c.

Superconductivity was discovered by Dutch physicist Heike Kamerlingh Onnes in 1911. He was awarded the Nobel Prize in Physics for this and other discoveries in 1913. To attain superconductivity, Kamerlingh Onnes found that he had to cool pure metals to within a few degrees of absolute zero (0 K or –273.16 ºC).

Since 1911, researchers have made materials with increasingly higher T_c values. By 2015, a hydrogen–sulfur compound that was formed under high pressure set the high-T_c record of –70º C, still too low for practical applications.

But just last month, the record was broken again. Maddury Somayazulu, Russell J. Hemley, and colleagues at George Washington University (Washington, DC), Carnegie Institution of Washington (DC), and Argonne National Laboratory (IL) made a compound with the empirical formula LaH₁₀¹ that exhibited a “hot” T_c of –13 ºC. This temperature is almost high enough to be practical; but the catch is that LaH₁₀, or lanthanum decahydride, is stable only at the pressure at which it is formed: ≈200 GPa or about 2 million times the Earth’s atmospheric pressure at sea level.

Now that superconductivity near ambient temperature has been achieved, the next step presumably will be to find a way to achieve similarly high-T_c materials that are stable at usable pressures.

1. The images shown here are for illustrative purposes only; the exact structure of LaH₁₀ has yet to be established.