The platinum group metals (PGMs) are a family of six structurally and chemically similar elements that include platinum (Pt), palladium (Pd), Rhodium (Rh), Iridium (Ir), Ruthenium (Ru), and Osmium (Os). Platinum jewelry may be the most well-known application of the PGMs, but most platinum is used in the manufacture of catalytic converters and other industrial applications. Now there may be a new use for platinum—as a superconductor.
Superconductors are materials that conduct electricity without resistance or loss of energy in extremely low temperatures. Superconducting materials already have many applications, but materials that will work at higher temperatures and lower costs are still needed.
According to a recent article on Phys.org, researchers from Japan’s Hokkaido University, Kyushu Institute of Technology, NEC Corporation, Keio University, and the National Institute for Materials Science have developed a new superconducting material based on platinum, which was thought to be unsuitable as a superconducting material. The article explains the process as follows:
The material was developed by mixing lanthanum (La), platinum (Pt) and arsenic (As) powders in a ratio of 1:5:1 and compressing them into pellets. These were then heated to 500°C for ten hours. The resultant material was ground and re-pelletized, then heated at 1000°C for an hour at various pressures. The team found that the final product (LaPt5As ) was non-superconducting at a pressure of five gigapascals (GPa) (equivalent to 50,000 bars of pressure), but became superconducting at 10 GPa, only to return to a non-superconductive state at 15 GPa.
The researchers examined the crystal structure of the superconducting LaPt5As. They revealed that platinum atoms formed multiple layers which piled up as high as 6 nm, the highest among metal superconductor. They also found that lanthanum and arsenic atoms separated platinum layers from each other in a way, they speculate, which weakens the interaction between platinum electrons, allowing them to flow more freely and resulting in the superconducting property.
The study was published in the Journal of the American Chemical Society.
While the potential discovery of a new superconducting material is good news, the fact that the material is platinum may present a supply problem. Production from platinum mines is diminishing, while demand for PGMs, particularly platinum, is expected to grow. According to the USGS 2016 Platinum Mineral Commodity Summary, increased automobile production, as well as more stringent emission standards for automobiles in many countries, is expected to result in increased demand for palladium, platinum, and rhodium for use in catalytic converters. However, the survey also estimates 125,000 kilograms of platinum, palladium, and rhodium was recovered globally from new and old scrap in 2015, including about 55,000 kilograms recovered from automobile catalytic converters in the United States.
Pyrometallurgical processes are favored for the recycling of PGM-bearing materials such as catalytic converters because of the high recovery rates. Primary PGMs must be separated from the base metals and impurities. Wavelength dispersive x-ray fluorescence (WDXRF) technology is well established for the analysis of the recovered metal in either scenario because it offers high sensitivity down to low atomic number elements, high repeatability, and element selectivity. WDXRF is also favored for its wide dynamic range and ability to achieve the performance levels needed for routine industrial applications.