Fresnoite: A new ferroelectric mineral
Fresnoite: A new ferroelectric mineral
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弗雷斯诺铁矿：一种新型铁电矿物
DOI：
10.1063/1.369541
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发表时间：
1999
影响因子：
3.2
通讯作者：
S. Abrahams
中科院分区：
文献类型：
--
作者：
M. Foster;D. Arbogast;R. Nielson;P. Photinos;S. Abrahams
Fresnoite，Ba_2TiOSi_2O_7，在结构上被预测为一种新的铁电体。交流和直流介电迟滞检测验证了预测。根据1.2 MV m−1 ac时的磁滞现象估算的自发极化Ps在295 K时为10.2C m−2，与一维铁电体中观察到的最小Ps相当。 多晶材料在433（2）K时熵变为0.19（3）J mol−1 K−1的可再现量热异常与先前在单晶中报道的小的介电和热电异常相一致;在810（5）K时熵变为<$0.2J mol−1 K−1也伴随着在805（5）K时陶瓷样品中观察到的介电异常。 两个量热异常的宽度都是1060 K。 在875 K下的介电滞后观测表明，这两种异常都不对应于居里温度;两者都可能与原子位置的微小变化有关，而不是与对称性变化有关。在1703（1）K时开始熔化，过冷度达435 K。
Fresnoite, Ba2TiOSi2O7, has been predicted structurally to be a new ferroelectric. Detection of both ac and dc dielectric hysteresis verifies the prediction. The spontaneous polarization Ps estimated from the hysteresis at 1.2 MV m−1 ac is ∼0.2 C m−2 at 295 K, comparable with the minimum Ps observed in one-dimensional ferroelectrics. A reproducible calorimetric anomaly with entropy change 0.19(3) J mol−1 K−1 at 433(2) K in polycrystalline material coincides with a small dielectric and pyroelectric anomaly previously reported in single crystals; an entropy change ∼0.2 J mol−1 K−1 at 810(5) K also accompanies a dielectric anomaly observable in ceramic samples at 805(5) K. Both calorimetric anomalies are ∼60 K wide. Observation of dielectric hysteresis at 875 K shows that neither anomaly corresponds to the Curie temperature; both are likely associated with small changes in atomic position, not with symmetry changes. Melting onset in fresnoite is 1703(1) K with undercooling as deep as 435 K.