Synthesis and Phase Transition of HgTiO₃

A rhomboidal distorted perovskite HgTiO ₃ with the unit cell parameters a = 5.3781 Å and c = 13.604 Å (Z = 6) was synthesized under 6 GPa at 600°C for 30 minutes, using a mixture starting material HgO and TiO ₂ in a closed Au-capsule. Through investigations on the relationship between its crystal structure and applied pressure by the synchrotron X-ray beam (wavelength = 0.72000 Å) at room temperature, we found a rhombohedral distortion decreased when the pressure increased and the symmetry approached to the cubic under a pressure of 2.3 GPa. Above room temperature, some abnormalities were observed from the measurements of differential scanning calorimetry (DSC) and dielectric property. These results suggested that HgTiO ₃ is a ferroelectrics at room temperature.

Keywords:

• Mercury titanate
• rhomboidal distorted perovskite
• high pressure synthesis
• phase transition
• ferroelectric

Acknowledgments

The authors acknowledge Prof. Ronald Miletich of University of Heidelberg, and Mr. David SAGER and Ms. Jennifer RUPP of ETH for the synchrotron radiation experiments at ESRF. We also thank Mr. Masayuki ONODERA and Mr. Yasushi EBIHARA of Utsunomiya University for the help of DSC measurements.

Paper originally presented at IMF-11, Iguassu Falls, Brazil, September 5–9, 2005; received for publication January 26, 2006.