常誘電体

paraelectric material

[目次：結晶等(結晶構造／材料試料)]

電場をかけると誘電分極が生じ、電場を取り去ると分極が0になる物質。電子が原子核に対して変位する電子分極、正イオンが負イオンに対して変位するイオン分極、永久双極子モーメントを持つ分子が電場によってその方向を変える配向分極がある。比誘電率や誘電損失は小さい。（フォノンの零点振動のために絶対零度付近でも強誘電相へ転移せず常誘電状態にとどまる物質を量子常誘電体という。）

"Paraelectric material" generates dielectric polarizations when an electric field is applied to the material and the material looses the polarizations when the electric field is removed. In "paraelectric materials," three kinds of polarizations exist: (1) electronic polarization, (2) ionic polarization, and (3) orientational polarization. In electronic polarization, electrons are displaced against the atomic nucleus. In ionic polarization, positive ions are displaced against negative ions. In orientational polarization, molecules having permanent dipole moments change their directions under an electric field. The paraelectric material has a small permittivity and a small dielectric loss. A material which is called quantum paraelectrics does not transform to a ferroelectric phase but remains at the paraelectric state even around absolute zero temperature due to zero-point oscillation of phonons.

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