Promethium bound: Rare earth element’s secrets exposed | ORNL (2024)

Scientists have uncovered the properties of a rare earth element that was first discovered 80 years ago at the very same laboratory, opening a new pathway for the exploration of elements critical in modern technology, from medicine to space travel.

Promethium bound: Rare earth element’s secrets exposed | ORNL (1)

This groundbreaking promethium research was led by, from left, Alex Ivanov, Santa Jansone-Popova and Ilja Popovs, all of ORNL. Credit: Carlos Jones/ORNL, U.S. Dept. of Energy

Promethium was discovered in 1945 at Clinton Laboratories, now the Department of Energy’s Oak Ridge National Laboratory, and continues to be produced at ORNL in minute quantities. Some of its properties have remained elusive despite the rare earth element’s use in medical studies and long-lived nuclear batteries. It is named after the mythological Titan who delivered fire to humans and whose name symbolizes human striving.

“The whole idea was to explore this very rare element to gain new knowledge,” said Alex Ivanov, an ORNL scientist who co-led the research. “Once we realized it was discovered at this national lab and the place where we work, we felt an obligation to conduct this research to uphold the ORNL legacy.”

The ORNL-led team of scientists prepared a chemical complex of promethium, which enabled its characterization in solution for the first time. Thus, they exposed the secrets of this extremely rare lanthanide, whose atomic number is 61, in a series of meticulous experiments.

“The whole idea was to explore this very rare element to gain new knowledge,” said Alex Ivanov, an ORNL scientist who co-led the research. “Once we realized it was discovered at this national lab and the place where we work, we felt an obligation to conduct this research to uphold the ORNL legacy.”

Their landmark study,published in the journal Nature, marks a significant advance in rare earth research and might rewrite chemistry textbooks.

“Because it has no stable isotopes, promethium was the last lanthanide to be discovered and has been the most difficult to study,” said ORNL’s Ilja Popovs, who co-led the research. Most rare earth elements are lanthanides, elements from 57 — lanthanum — to 71 — lutetium — on the periodic table. They have similar chemical properties but differ in size.

The other 14 lanthanides are well understood. They are metals with useful properties that make them indispensable in many modern technologies. They are workhorses of applications such as lasers, permanent magnets in wind turbines and electric vehicles, X-ray screens and even cancer-fighting medicines.

“There are thousands of publications on lanthanides’ chemistry without promethium. That was a glaring gap for all of science,” said ORNL’s Santa Jansone-Popova, who co-led the study. “Scientists have to assume most of its properties. Now we can actually measure some of them.”

The research relied on unique resources and expertise available at DOE national laboratories. Using a research reactor, hot cells and supercomputers, as well as the accumulated knowledge and skills of 18 scientists in different fields, the authors detailed the first observation of a promethium complex in solution.

Promethium bound: Rare earth element’s secrets exposed | ORNL (2)

Conceptual art shows the rare earth element promethium in a vial surrounded by an organic ligand. ORNL scientists have discovered hidden features of promethium, opening a pathway for research into other lanthanide elements. Credit: Jacquelyn DeMink, art; Thomas Dyke, photography/ORNL, U.S. Dept. of Energy

The ORNL scientists bound, or chelated, radioactive promethium with special organic molecules called diglycolamide ligands. Then, using X-ray spectroscopy, they determined the properties of the complex, including the length of the promethium chemical bond with neighboring atoms — a first for science and a longstanding missing piece to the periodic table of elements.

Promethium is very rare; only about a pound occurs naturally in the Earth’s crust at any given time. Unlike other rare earth elements, only minute quantities of synthetic promethium are available because it has no stable isotopes.

For this study, the ORNL team produced the isotope promethium-147, with a half-life of 2.62 years, in sufficient quantities and at a high enough purity to study its chemical properties. ORNL is the United States’only producer of promethium-147.

Notably, the team provided the first demonstration of a feature of lanthanide contraction in solution for the whole lanthanide series, including promethium, atomic number 61. Lanthanide contraction is a phenomenon in which elements with atomic numbers between 57 and 71 are smaller than expected. As the atomic numbers of these lanthanides increase, the radii of their ions decrease. This contraction creates distinctive chemical and electronic properties because the same charge is limited to a shrinking space. The ORNL scientists got a clear promethium signal, which enabled them to better define the shape of the trend — across the series.

“It’s really astonishing from a scientific viewpoint. I was struck once we had all the data,” said Ivanov. “The contraction of this chemical bond accelerates along this atomic series, but after promethium, it considerably slows down. This is an important landmark in understanding the chemical bonding properties of these elements and their structural changes along the periodic table.”

Promethium bound: Rare earth element’s secrets exposed | ORNL (3)

Team members at ORNL’s Radiochemical Engineering Development Center, where the promethium sample was purified, included, from left, Richard Mayes, Frankie White, April Miller, Matt Silveira and Thomas Dyke. Credit: Carlos Jones/ORNL, U.S. Dept. of Energy

Many of these elements, such as those in the lanthanide and actinide series, have applications ranging from cancer diagnostics and treatment to renewable energy technologies and long-lived nuclear batteries for deep space exploration.

The achievement will, among other things, ease the difficult job of separating these valuable elements, according to Jansone-Popova. The team has long worked on separations for the whole series of lanthanides, “but promethium was the last puzzle piece. It was quite challenging,” she said. “You cannot utilize all these lanthanides as a mixture in modern advanced technologies, because first you need to separate them. This is where the contraction becomes very important; it basically allows us to separate them, which is still quite a difficult task.”

The research team used several premier DOE facilities in the project. At ORNL, promethium was synthesized at the High Flux Isotope Reactor, a DOE Office of Science user facility, and purified at the Radiochemical Engineering Development Center, a multipurpose radiochemical processing and research facility. Then, the team performed X-ray absorption spectroscopy at the National Synchrotron Light Source II, a DOE Office of Science user facility at DOE’s Brookhaven National Laboratory, specifically working at the Beamline for Materials Measurement, which is funded and operated by the National Institute of Standards and Technology.

The team also performed quantum chemical calculations and molecular dynamics simulations at the Oak Ridge Leadership Computing Facility, a DOE Office of Science user facility at ORNL, using the lab’s Summit supercomputer, the only computational resource capable of providing the necessary calculations at the time. In addition, the researchers used resources of the Compute and Data Environment for Science at ORNL. They expect future calculations to be performed on ORNL’s Frontier, the world’s most powerful supercomputer and the first exascale system, which is able to perform more than a quintillion calculations each second.

Promethium bound: Rare earth element’s secrets exposed | ORNL (4)

The promethium research team, standing in front of ORNL’s Radiochemical Engineering Development Center, included, from left, Santanu Roy, Thomas Dyke, Ilja Popovs, Richard Mayes, Darren Driscoll, Frankie White, Alex Ivanov, April Miller, Subhamay Pramanik, Santa Jansone-Popova, Sandra Davern, Matt Silveira, Shelley VanCleve and Jeffrey Einkauf. Credit: Carlos Jones/ORNL, U.S. Dept. of Energy

Popovs emphasized that the ORNL-led accomplishments can be attributed to teamwork. Each of the Nature paper’s 18 authors was critical to the project, he said.

The achievement sets the stage for a new era of research, the scientists said. “Anything that we would call a modern marvel of technology would include, in one shape or another, these rare earth elements,” Popovs said. “We are adding the missing link.”

Besides Popovs, Ivanov and Jansone-Popova from ORNL’s Chemical Sciences Division, the paper’s co-authors include Darren Driscoll, Subhamay Pramanik, Jeffrey Einkauf, Santanu Roy and Thomas Dyke, also of ORNL’s Chemical Sciences Division; Frankie White, Richard Mayes, Laetitia Delmau, Samantha Cary, April Miller and Sandra Davern of ORNL’s Radioisotope Science and Technology Division; Matt Silveira and Shelley VanCleve of ORNL’s Isotope Processing and Manufacturing Division; Dmytro Bykov of the National Center for Computational Sciences at ORNL; and Bruce Ravel of the National Institute of Standards and Technology.

This work was primarily co-sponsored by DOE’s Office of Science for ligand synthesis, lanthanide complexation studies, crystallization processes, spectroscopic analyses and simulation efforts. The production, purification and preparation of the promethium samplewere supported by the DOE Isotope Program, managed by the Office of Science for Isotope R&D and Production. The single-crystal X-ray diffraction data collection and refinement weresupported by the DOE Office of Science.

UT-Battelle manages ORNL for DOE’s Office of Science, the single largest supporter of basic research in the physical sciences in the United States. The Office of Science is working to address some of the most pressing challenges of our time. For more information, please — Lawrence Bernard and Leo Williams

Learn more about the original discovery of promethium at ORNL

Promethium bound: Rare earth element’s secrets exposed | ORNL (2024)


Is promethium a rare earth element? ›

promethium (Pm), chemical element, the only rare-earth metal of the lanthanide series of the periodic table not found in nature on Earth.

What are 2 interesting facts about promethium? ›

Interesting Promethium Facts

The element is named for Prometheus, the Titan who stole fire from the Greek gods to give to mankind. Promethium was the last rare earth element of the lanthanide series to be discovered. It was discovered in 1945 by Jacob A. Marinsky, Lawrence E.

What does promethium decay into? ›

Promethium does not occur naturally on earth, although it has been detected in the spectrum of a star in the constellation Andromeda. Promethium's most stable isotope, promethium-145, has a half-life of 17.7 years. It decays into neodymium-145 through electron capture.

Can promethium be found in nature? ›

Natural abundance

Promethium's longest-lived isotope has a half-life of only 18 years. For this reason it is not found naturally on Earth.

What is the rarest element to ever exist? ›

Astatine is the rarest naturally occurring element.

What is promethium used for in everyday life? ›

Most promethium is used for research purpose. It can be used as beta radiation source in luminous paint, in nuclear batteries for guided missiles, watches, pacemakers and rados, and as a light source for signals. It is possible that in future it will be used as portable X-ray source.

What happens when promethium reacts with water? ›

Reaction of promethium with water

However, one would predict that the silvery white metal promethium is quite electropositive and would react slowly with cold water and quite quickly with hot water to form promethium hydroxide, Pm(OH)3, and hydrogen gas (H2).

Does promethium glow in the dark? ›

Scientific element: Promethium

It is extremely rare on Earth, although it has been detected in specimens from the radioactive decay of uranium. It is silvery white and the salts glow in the dark with a pale blue or green light.

Is promethium magnetic? ›

Yes, promethium is somewhat magnetic. Although it is not one of the elements to exhibit ferromagnetism, it is paramagnetic.

Is promethium toxic to humans? ›

Promethium is a radioactive metal, and its salts are highly toxic if ingested. If promethium comes into contact with the skin, it can cause burns. Inhaling promethium dust can lead to lung damage. If you must handle promethium, always wear gloves and protective clothing.

Can promethium be used as fuel? ›

Promethium is also utilised as the Imperial military forces' standard vehicle fuel, used in main battle tanks as well as other armoured vehicles and aircraft.

How much promethium is on earth? ›

All of its isotopes are radioactive; it is extremely rare, with only about 500–600 grams naturally occurring in Earth's crust at any given time.

How rare is promethium? ›

Promethium is a chemical element; it has symbol Pm and atomic number 61. All of its isotopes are radioactive; it is extremely rare, with only about 500–600 grams naturally occurring in Earth's crust at any given time.

What is considered a rare earth element? ›

The rare earth elements (REE) are a set of seventeen metallic elements. These include the fifteen lanthanides on the periodic table plus scandium and yttrium. Rare earth elements are an essential part of many high-tech devices.

What are 14 the rare earth elements include? ›

The rare earth elements include the lanthanide series, scandium and yttrium. They are a set of seventeen chemical elements in the periodic table. They really are not that rare but they occur together in nature and are hard to separate from one another.

Are there 19 rare earth elements? ›

The 17 rare earth elements consist of the 15 lanthanide series on the periodic table as well as scandium and yttrium. These silver to silvery-white lustrous metals are often malleable and exhibit special properties, which helps to explain why they can be utilized in a range of industrial applications.

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