Single crystals currently used in semiconductors, electronic devices, and optical equipment cannot withstand high temperatures. This is because the materials typically used to make them, such as iridium and platinum, have melting points below 2,200°C. Creating single crystals that can withstand these extreme temperatures has been a challenge that has remained unsolved to date.

From left to right: Schematic diagram of a new crystal growth technique using a tungsten crucible and deoxidized insulator, and an example of a new single crystal.

Source: Scientific Reports (2025)

Associate Professor Yui Yokota and Professor Akira Yoshikawa (Tohoku University's Institute for Materials Research) have developed a new crystal growth technique using a tungsten (W) crucible that can be used at temperatures exceeding 2,200°C.

This crystal growth technique is expected to significantly contribute to the discovery of new materials and the mass production of single crystals of higher-melting-point oxides.

The research was published in Scientific Reports.

"Tungsten has previously been unsuccessful because it readily reacts with oxides," Yokota explained. "Tungsten can also be incorporated into the crystal, contaminating the final product."

The research team developed a new crystal growth technique that suppresses unwanted reactions and contamination. Their research clarified the mechanisms behind these processes, enabling them to be effectively prevented.

Ultimately, they have successfully developed high-density single crystals that surpass those of existing scintillators. This discovery has the potential to have significant practical implications, directly improving the lives of people around the world. For example, these crystals could be used in PET devices to detect cancer at an earlier stage in a shorter time.

Melting points and band gaps of existing oxide, fluoride, and halide scintillator single crystals. The figure shows the regions where crystals can be grown using iridium, platinum-rhodium, and platinum crucibles.

Source: Scientific Reports (2025)

"These results are exciting because they mean we can create a vast array of new materials suitable for a wide range of applications," says Yoshikawa.

This research is expected to accelerate the development of new functional single crystals operating at temperatures above 2200°C for use in semiconductors, optical materials, scintillators, and piezoelectric materials. Mass production methods are currently being developed with support from the Japan Science and Technology Agency (JST).

Source: Content compiled from phys

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