Synthesis and Dielectric Characterization of Potassium Niobate Tantalate Ceramics
Synthesis and Dielectric Characterization of Potassium Niobate Tantalate Ceramics
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DOI：
10.1111/j.1551-2916.2005.00606.x
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发表时间：
2005-12
影响因子：
3.9
通讯作者：
J. Venkatesh;V. Sherman;N. Setter
中科院分区：
文献类型：
--
作者：
J. Venkatesh;V. Sherman;N. Setter
为了探索该材料在铁电可调谐领域的应用潜力，研究了该材料的制备和介电性能。采用常规空气烧结和单轴热压两种方法制备了样品。两种方法的相对平均密度均大于92%。两种方法制备的样品均存在Nb/Ta不均匀分布，但热压样品的不均匀程度较低。与已报道的单晶烧结结果相比，两种烧结过程都导致陶瓷的转变温度较低，但热压样品的介电常数最大温度(T-max)与空气中烧结的样品相比有相对上移。所有样品的介电性能都表现出很强的频散特性。利用Landau-Devonshire模型对室温下的直流偏置效应进行了测量和模拟。结果表明，KTN的非线性系数β与文献报道的KNbO_3和SrTiO_3单晶的值相当，对调谐应用具有重要意义。在20kV/cm下，烧结陶瓷和热压陶瓷的室温介电调谐率分别为16%和42%。损耗正切，在兆赫频率下很低，在低千兆赫频率下增加到9%-17%。这被认为与由于带电缺陷而在陶瓷中观察到的频率色散有关。
The preparation and dielectric properties of potassium niobate tantalate (KTN) have been investigated with the aim of exploring the material's potential for ferroelectric tunable applications. The samples were prepared both by conventional sintering in air and by uniaxial hot pressing. A relative average density greater than 92% was obtained with both methods. An inhomogeneous Nb/Ta distribution was found in the samples prepared by both methods, but the inhomogeneity extent was lower in the hot-pressed samples. While both sintering processes resulted in ceramics of lower transition temperatures in comparison with the reported results on single crystals, a relative up shift of the temperature (T-max) at which the dielectric constant is maximum was found for hot-pressed samples compared with that of samples sintered in air. All the samples exhibited strong frequency dispersion in dielectric properties. The effect of DC bias at room temperature was measured and modeled using the Landau-Devonshire model. It was found that the nonlinear coefficient beta of KTN, which is important for tunable applications, is comparable with the value reported on KNbO3 and SrTiO3 single crystals. A dielectric tunability of 16% and 42% at room temperature was demonstrated under 20 kV/cm for the sintered and hot-pressed ceramics, respectively. The loss tangent, low at megahertz frequencies, was augmented to 9%-17% at low gigahertz frequencies. This is believed to be related to the frequency dispersion observed in the ceramics because of charged defects.