Ferroic phase transitions in (Na1/2Bi1/2)TiO3 crystals
Ferroic phase transitions in (Na1/2Bi1/2)TiO3 crystals
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DOI：
10.1111/j.1151-2916.1996.tb08586.x
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发表时间：
1996-05
影响因子：
3.9
通讯作者：
Seung-Eek Park;Su-jin Chung;In-Tae Kim
中科院分区：
文献类型：
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作者：
Seung-Eek Park;Su-jin Chung;In-Tae Kim
研究了助熔剂法和提拉法生长的（Na 1/2Bi 1/2）TiO 3（NBT）晶体的铁性相变行为。虽然NBT的四面体和菱形相都被认为是铁弹的，但这些晶体表现出不同的铁弹行为。两种NBT晶体的温度滞后量和热膨胀系数也存在差异。这些差异可归因于非化学计量和取决于生长方法的结构变化。目前的研究揭示了介电常数（e（T））曲线在2450 °C下的第二个最大值，这可能表明中间的四方相是极性的或反极性的。然而，这个最大值源于空间电荷极化和电荷载流子与电极之间的相互作用，使得四极相实际上是顺电的。因此，NBT晶体的扩散相变（DPT）是从顺电和铁弹四面体相到铁电和铁弹菱形相。讨论了NBT晶体铁性相变中的晶体学超群-子群关系。
The ferroic phase-transition behavior of two (Na 1/2 Bi 1/2 )TiO 3 (NBT) crystals grown by flux and by the Czochralski method has been investigated in the present study. Although both the tetragonal and the rhombohedral phases of NBT are expected to be ferroelastic, these crystals exhibit different ferroelastic behavior. The two NBT crystals also show differences in the amount of temperature hysteresis and the thermal expansion coefficients. These differences can be attributed to nonstoichiometry and structural variations dependent on the growing method. The present investigation has revealed a second maximum at ∼450°C in dielectric constant (e(T)) curves, which could indicate that the intermediate tetragonal phase is either polar or antipolar. This maximum, however, originates from space-charge polarization and interaction between the charge carrier and the electrode, such that the tetragonal phase, in fact, is paraelectric. The diffuse phase transition (DPT) of the NBT crystal, therefore, is from a paraelectric and ferroelastic tetragonal phase to a ferroelectric and ferroelastic rhombohedral phase. The crystallographic supergroup-subgroup relationships in the ferroic phase transitions of NBT crystals are discussed.