Since the discovery of the ferroelectric perovskite-type oxide BaTiO3 in 1943, numerous materials have
been surveyed as candidates for new ferroelectrics. Perovskite-type materials have played a leading role in
basic research and applications of ferroelectric materials since the last century. Experimentalists and theoreticians
have developed a new materials design stream for post-perovskite materials. In this stream, we
have mainly focused on the role of covalency in the evolution of ferroelectricity for displacive-type ferroelectrics
in oxides. This perspective surveys the following topics: (1) crossover from quantum paraelectric
to ferroelectric through a ferroelectric quantum critical point, (2) the role of cation–oxygen covalency in
ferroelectricity and the crossover to quantum paraelectric in perovskite-type compounds, (3) off-centerinduced
ferroelectricity in perovskites, (4) second-order Jahn–Teller effect enhancement of ferroelectricity
in lithium-niobate-type oxides, (5) the presence of four ferroelectric phases and structural transitions
of phases of AFeO3 with decreasing radius of A (A = La–Al), (6) tetrahedral ferroelectrics of perovskiterelated
Bi2SiO5 and wurtzites, (7) a rare type of polarization switching system in which the coordination
number of ions in κ-Al2O3 systems changes between 4 and 6, and (8) lone-pair-electron-induced ferroelectrics
in langasite-type compounds.
各種検索
サポート
ヘルプ