Colossal negative thermal expansion in a Bi-based perovskite
Jun. 15, 2011
The unusual property of negative thermal expansion (NTE) has been found in a Bi-based perovskite of Bi0.95La0.05NiO3. The linear expansion coefficient of -82 × 10-6 K-1 is observed between 320 and 380 K from a dilatometric measurement on a ceramic pellet. The value is more than three times that of other materials showing NTE near room temperature. This new material may be used to fabricate zero or controlled expansion composites.
First, the investigation was conducted into the template material of BiNiO3. Neutron diffraction experiments under high pressure (HP) and high temperature (HT) revealed that BiNiO3 shows large volume reduction with increasing temperature under pressure due to a first order phase transition. X-ray absorption measurements at HP&HT elucidated that the transition is associated with a Bi/Ni charge transfer.
Next, partial substitution of La for Bi was performed in order to impede the charge transfer. As a consequence, transition pressure and temperature were successfully lowered and the NTE property appeared at ambient condition. In addition, the impurity effect leads to the smooth volume shrinkage on heating. Moreover, NTE temperature range is controllable by the amount of La substitution.
These achievements were published in Nature Communications at 14th Jun 2011. This work was carried out by a joint research group that consisted of Kyoto University, JASRI, JAEA, University of Tokyo, Hiroshima University, and University of Edinburgh and Rutherford Appleton Lab.
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