Yuji Masubuchi 교수

Oxynitride perovskites, having oxide and nitride anions together in a compound, are a new class of dielectric material. The shaping process in either bulk ceramics or thin films is an essential factor for investigating and utilizing the dielectric properties of these materials. In this perspective, recent studies on the shaping of dielectric oxynitride perovskites are reviewed with a consideration of the powder preparation and thermal stability for sintering, several sintering methods, ultra-hig

Perovskite-type oxynitride BaTaO₂N has been attracting attention for its large dielectric constant, which is almost independent of the temperature by measurements on its ceramics. Its dielectric characteristics are attributed to polar nanoregions (PNRs) in the average cubic crystal structure. Polarization saturation to produce a butterfly-like piezoresponse force microscopy (PFM) signal was observed on BaTaO₂N crystals in the present study. Reddish crystallites of BaTaO<sub

A new tetragonal BaCN₂ polymorph was obtained <italic>via</italic> a simple nitridation reaction of BaCO₂, and the Eu doped product showed a red emission with an extremely wide range of red-shift of the emission wavelength with decreasing temperature.

We report a new material, BaCN2:Eu 2+ for a very sensitive optical pressure sensor, 50 times more sensitive than ruby. Photoluminescence spectra of the BaCN2:Eu 2+ phosphor was measured under hydrostatic pressures from ambient pressure to 5.34 GPa at room temperature. The peak wavelength of the luminescence was drastically red-shifted at a rate of 19 nm/GPa, which is approximately 50 times larger than that of the ruby, most commonly used as a pressure sensor in the high-pressure experiments. Thi

The perovskite-type oxynitride SrTaO2N was synthesized from Sr2Ta2O7 and carbon nitride (C3N4) and the formation mechanism was investigated using X-ray diffraction and thermogravimetry combined with mass spectrometry. In this process, ammonia is not required for the nitridation of the oxide. The C3N4 thermally decomposes to gaseous C2N2, which forms SrCN2 and Ta3N5 intermediates on the Sr2Ta2O7. These intermediates then react with the oxide to form SrTaO2N at 800 °C, which is 200 °C lower than t

Solid phase sintering of dielectric oxynitride perovskites above 1000 °C is accompanied by their decomposition. Post-ammonolysis is required to recover their stoichiometric nitrogen content and dielectric properties. In the present work, the oxynitride perovskite SrTaO₂N was sintered with a BaCN₂ flux at approximately 900 °C avoiding its thermal decomposition. The resulting solid product with a relative density of 68.9% showed relative dielectric constants in the range from