A very unique material with outstanding heat-storage properties has been reported this month in Nature Communications. The research group of Shin-ichi Ohkoshi at the University of Tokyo have synthesised a lambda-trititanium pentoxide, λ-Ti3O5, which exhibits a solid–solid phase transition to beta-trititanium pentoxide, β-Ti3O5. This feature makes possible the storage of a large latent heat energy (230 kJ/L) that can be released by applying a small external pressure (~60 MPa) only when demanded. In general, such heat-storage materials cannot store the energy for a prolonged period.
Images of the different phases of Ti3O5 produced by a change of pressure and in current. Below is the heat energy released by application of pressure at t=0. Images from Nature Communications.
The development of high-performance heat-storage materials is important for a more efficient use of waste heat in factories and residences. Moreover, λ-Ti3O5 is a metallic conductor and β-Ti3O5 is a semiconductor, this offers possibilities to realise pressure-sensitive conductivity sensor or pressure-sensitive optical sensor. On top of this, light-induced and current-induced phase transitions from pressure-produced β-Ti3O5 to λ-Ti3O5 are also possible, which are very attractive for advanced electronic devices.
It is not easy to find a material with such outstanding properties and offering the possibilities to apply its unique features in a wide range of applications.