Geometric ferroelectricity in rare-earth compounds RGaO3 and RInO3

What is it about?

Unconventional ferroelectricity that is driven by geometric factors (ionic size effects) has been theoretically investigated in rare-earth oxides RGaO3 and RInO3. In-situ high temperature x-ray diffraction (XRD) experiments verified the compounds’ crystal structure and phase transition around 1573 K (1300 degree Celsius).

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Photo by Abolfazl Pahlavan on Unsplash

Photo by Abolfazl Pahlavan on Unsplash

Why is it important?

Ferroelectric and piezoelectric materials are widely used in electronics applications such as capacitors and actuators. Most of these compounds contain specific active cations of Ti4+ and Nb5+ (so-called d0 ions) or Pb2+ and Bi3+ (so-called s2 lone-pair ions). Because some of these elements have toxicity (e.g. Pb), development of new (lead-free) ferroelectrics and piezoelectrics are desired. The geometric ferroelectricity does not rely on specific kinds of elements and an exploration of geometric ferroelectrics should broaden research frontiers of ferroelectric materials.