Room-temperature Ferroelectricity in Bulk Hafnia

July 1, 2021
A Rietveld refinement of the neutron powder diffraction data with the fit (red), data points (black), predicted Bragg positions for Pca21 (green vertical bars), and the difference curve (blue). Inset shows the crystal structure of Pca21 phase. The red arrows indicate the local polarization.

Scientific Achievement

The polar orthorhombic Pca21 ferroelectric phase of HfO2, previously seen at room temperature only in thin films, has been stabilized in a bulk single crystal through yttrium doping.

Significance and Impact

This study provides insight into the polymorphic nature and phase control of HfO2 and shows how to produce bulk ferroelectricity in this material, providing a new route to next-generation ferroelectric devices.

Research Details

  • Positive up, negative down (PUND) polarization measurements confirmed bulk ferroelectricity at room temperature.
  • Single crystals were grown by a floating zone technique.
  • Neutron powder diffraction on ground single crystals showed that the origin of ferroelectricity in 12% HfO2:Y is the polar orthorhombic Pca21 crystal structure.
  • Samples were further characterized by electron microscopy.

“Kinetically stabilized ferroelectricity in bulk single-crystalline HfO2:Y”

Xianghan Xu, Fei-Ting Huang, Yubo Qi, Sobhit Singh, Karin M. Rabe, Dimuthu Obeysekera, Junjie Yang, Ming-Wen Chu, and Sang-Wook Cheong,

Nature Materials, 20, 826–832, (2021).