MOSCOW, June 6, Vladislav Strekopytov. A new generation of superconductors, which are so needed in many high-tech industries, will be based on palladium compounds, the researchers report. This is beneficial for Russia — the country has most of the world's reserves of this rare and expensive metal, as well as almost half of its entire production.
Zero resistance
In 1911, the Dutch physicist Kamerling-Onnes discovered that the electrical resistance of solid mercury when cooled in liquid helium to 4.1 Kelvin (minus 269 degrees Celsius) drops sharply to zero. This was the first officially recorded case of superconductivity.
Soon, several more superconductors were identified. The transition temperature (Tc) of all was extremely low, close to absolute zero.
In 1986, Karl Müller and Georg Bednorz, an IBM research team, discovered a material with a Tc of 30 Kelvin, lanthanum and barium cuprate. . They were awarded the Nobel Prize in Physics for this.
< h3 id="1876218197-2">The main race of modern physics
In industry, devices and wires are cooled with liquid nitrogen, which boils at 77 Kelvin. Superconductors with Tc above this value are called high-temperature superconductors (HTSC).
In the 1990s, a number of compounds were obtained from the cuprate group with Tc 130-150 Kelvin. The most famous is BSCCO, or, as physicists call it, «bisco», consisting of layers of oxides of bismuth, strontium, copper and pure calcium.
High-temperature superconductors are already used in lossless energy transmission systems, non-contact high-speed trains, super-strong magnets for accelerators and thermonuclear reactors, super-efficient microchips, ultra-precise medical diagnostic devices, engines for interplanetary spacecraft. For example, tens of kilometers of wires were made from BSCCO at the Large Hadron Collider at CERN.
A real race has unfolded for ever higher temperature superconductors. Superconductivity at room temperature and normal pressures could radically change technologies and energy. However, no such compound has yet been found.
Cuprates, nickelates
Cuprates are complex compounds based on copper oxides, under normal conditions practically non-conductive, i.e. insulators.
They were singled out in a separate group of «strange metals», or superconducting semimetals. It is believed that quantum principles must be applied to describe the behavior of electrons in them, some researchers even see cuprates as a special state of matter.
Physicists at Cornell University and the Flatiron Institute in New York in 2020 built a digital model using quantum computing » strange metals», showing that cuprates are something between classical metals with mobile electrons and dielectrics in which electrons occupy fixed positions.
In 1999, Russian scientist Vladimir Anisimov and colleagues suggested that nickelates, complex compounds based on nickel oxide, could also have high-temperature superconductivity. Indeed, several nickel-containing HTSCs were subsequently discovered.
At one time there was even talk of entering the era of nickel superconductors. But there were problems. First, obtaining nickelates is an extremely complex process. Secondly, these compounds, although closer in properties to metals, are less stable than cuprates. This is explained by the fact that the energy states of nickel electrons are higher than those of copper, so they more actively enter into various interactions.
The era of palladium
the other is stronger than in cuprates, but weaker than in nickelates. Physicists from Japan and Austria pointed to palladium compounds — palladates.
“Palladium is one line below nickel in the periodic table,” lead researcher Carsten Held, from the Institute of Solid State Physics at the Technical University of Vienna, said in a press release. electronic interaction between them is weaker».
Palladates have an ideal electronic configuration for high temperature superconductivity. By building a model with variables such as the electron interaction strength, duty cycle, and pulse energy dispersion, the researchers determined the superconductivity band in palladates and mapped out two compounds with the highest Tc, around 100 Kelvin: RbSr2PdO3 and (Ba0.5La0.5)2PdO2Cl2.< br />The authors hope that their fellow experimenters will synthesize these materials and test their properties in the laboratory.
«The results of the calculations are promising,» notes Professor Held. «If a new class of superconductors appears, it will advance all research and allow a better understanding of superconductivity in general.»
For Russia, which has the world's largest reserves of palladium, this is good news. The deposits are located in the Norilsk region and on the Kola Peninsula.
Palladium's primary use is in the catalytic converters of automotive combustion engines. This metal is also used in electronics, medicine, the chemical industry, and in the manufacture of jewelry. Due to high-temperature superconductivity based on palladates, the demand for it can rise sharply.
«This will actually form a new sphere of consumption of palladium with a volume of up to 100 tons per year,» says industrial expert, candidate of economic sciences Leonid Khazanov. «Russia is able to occupy 20-30% the world HTSC market.»
The difficulty is that palladium is very rare and expensive. The price is two thousand dollars per ounce (about 31 grams) and the production is not millions of tons, like copper and nickel, but about 250 per year.