The single crystals currently used in semiconductors, electronic devices, and optical devices can't take the heat. This is because the materials typically used to make them - such as Iridium and Platinum - have a melting point below 2,200 °C. Creating single crystals that can withstand these extreme temperatures is a challenge that has been unmet until now.
Associate Professor Yuui Yokota and Professor Akira Yoshikawa (Institute for Materials Research, Tohoku University) have developed a new crystal growth technology using a tungsten (W) crucible that can be used in temperatures over 2,200°C. This crystal growth technology is expected to make significant contributions to the discovery of new materials and the mass-production of oxide single crystals with a higher melting point.
The research was published in Scientific Reports on August 8, 2025.
"The reason tungsten wasn't successful before now is because of its tendency to react with oxide materials," explains Yokota. "It can also get mixed in with the crystal - which contaminates the final product."
The team of researchers developed a new crystal growth technology that suppresses unwanted reactions and contamination. Their research clearly defined the mechanism behind these processes in order to properly put a stop to them. As a result, they have already succeeded in developing high-density single crystals that exceed those of existing scintillators. This finding has significant real world impact that can directly improve the lives of people around the world. For example, these crystals can be applied to a PET device to detect early-stage cancer in a shorter amount of time.
"These are exciting results, because it means we can create a plethora of new materials for a wide range of applications," says Yoshikawa.
This research is expected to help accelerate the development of new functional single crystals that operate above 2,200°C for semiconductors, optical materials, scintillators, and piezoelectric materials. The mass production method is currently under development with the support of The Japan Science and Technology Agency (JST).