Relaxor behaviour of low lead and lead free ferroelectric ceramics of the Na0.5Bi0.5TiO3–PbTiO3 and Na0.5Bi0.5TiO3–K0.5Bi0.5TiO3 systems
Relaxor behaviour of low lead and lead free ferroelectric ceramics of the Na0.5Bi0.5TiO3–PbTiO3 and Na0.5Bi0.5TiO3–K0.5Bi0.5TiO3 systems
复制标题
DOI：
10.1016/s0955-2219(01)00012-7
复制
发表时间：
2001
影响因子：
5.7
通讯作者：
Senda Saı̈d;J. Mercurio
中科院分区：
文献类型：
--
作者：
Senda Saı̈d;J. Mercurio
采用热分解法制备了Na0.5Bi0.5TiO3-PbTiO3系和Na0.5Bi0.5TiO3-K0.5Bi0.5TiO3系陶瓷。用变温X射线衍射仪、差示扫描量热仪和阻抗测量等方法研究了铁电材料在较宽的温度和频率范围内的铁电向顺电相变。与纯NBT相比，富NBT固溶体的介电常数和介电损耗都表现出强烈的温度和频率依赖性。随着频率的增加，介电常数减小，其最大值向高温方向移动。在高温范围内，介电常数的热变化符合定律1ε−1εm=C T−TMγ，γ接近1.5。这种松弛行为可以用阳离子无序来解释，这种无序是由于(Na，Bi)和Pb(或Na和K)的统计重新分配引起的。这将是一个非常罕见的与类钙钛矿型材料的A位占据相关的弛豫现象。
Ceramics with compositions belonging to the Na0.5Bi0.5TiO3–PbTiO3and Na0.5Bi0.5TiO3–K0.5Bi0.5TiO3systems were fabricated by natural sintering of powders prepared by thermal decomposition of adequate precursor solutions. The ferroelectric to paraelectric phase transitions were studied by variable temperature X-ray diffractometry, differential scanning calorimetry and impedance measurement in a wide range of temperature and frequency. In contrast with pure NBT, both the permittivity and dielectric loss of the NBT-rich solid solutions show a strongly temperature and frequency dependent behaviour. The permittivity decreases and its maximum is shifted towards high temperatures as the frequency increases. In the high temperature range, the thermal variation of the permittivity is well described by a law 1 ε − 1 εm=C T−Tmγwith γ close to 1.5. Such a relaxor-like behaviour is interpreted in terms of cation disorder due to the statistical repartition of (Na,Bi) and Pb (or Na and K). This would be one very rare case of relaxor phenomena correlated with the A-site occupancy in perovskite-like materials.