International collaborative research project for the development of environmentally friendly functional oxide materials

Research Summary

In order to realize an internet of things (IoT) society in which all devices are connected to the Internet, it is important to reduce the power consumption of electronics while developing materials that have a low environmental impact. We are designing novel materials through first principle calculations and conducting, precise structural analyseis of these materials using quantum beam and advanced characterization techniques,. This approach allows us to develop innovative and environmentally friendly functional materials, such as ferromagnetic ferroelectrics, which can be used in low power non-volatile memory applications, lead-free piezoelectrics that can be used to harvest electric energy from wind, as well as vibration and negative thermal expansion materials that absorb thermal distortion resulting from changes in air temperature.

  1. Development of ferromagnetic materials for high-performance magnetic memory
    Although magnetic memory (such as an HDD memory) has excellent temperature stability, a disadvantage of this technology is the relatively high power consumption arising from the need to generate a magnetic field by applying current to a coil for writing. The development of a multiferroic material allowing magnetization reversal through electric polarization reversal in which ferromagnetism and ferroelectricity coexist, promises ultra-low power consumption magnetic memory with electric field writing and magnetic reading. We are currently working to adapt the electric field applied magnetization reversal phenomenon observed in cobalt substituted bismuth ferrite thin films that was discovered here at Tokyo Tech to such a magnetic memory device.
  2. Using non-lead piezoelectric materials to reduce the environmental impact of electronic devices
    Piezoelectric materials that convert motion and electric signals are used as sensors and actuators in various devices, such as ultrasonic diagnostic machines and inkjet printers. However, the high proportion of lead by weight (60% or more) in widely used perovskite type oxides PbZr1-xTixO3 (PZT) is a major environmental concern. We are developing lead-free piezoelectric materials using bismuth with properties similar to lead to design a crystal structure similar to that of PZT.
  3. Development of negative thermal expansion materials for use in the energy industry

    Misalignment due to thermal expansion and the peeling of heterojunction interfaces are recognized as urgent issues in electronic devices including power devices and energy/environmental technologies such as fuel cells. BiNi0.85Fe0.15O3, another material developed at Tokyo Tech, shows striking negative thermal expansion that is five times that of existing materials and is therefore expected to be useful in the suppression of thermal expansion. However, as this material requires high pressure synthesis (similar to artificial diamond synthesis) it has not been mass produced. By adopting soft chemistry techniques, we are devising new means of synthesis under milder conditions to facilitate industrialization.

Lead-free piezoelectric material BiFe1-xCoxO3. Lead-free piezoelectric material BiFe1-xCoxO3.
Observation of magnetization reversal by electric field. Observation of magnetization reversal by electric field.