Institute for Materials Research, University of Leeds, Leeds, UK.
IEEE Trans Ultrason Ferroelectr Freq Control. 2011 Sep;58(9):1819-25. doi: 10.1109/TUFFC.2011.2019.
A phase-diagram for the Na(0.5)K(0.5)NbO(3)-LiTaO(3) solid solution series (NKN-LT) is presented for compositions ≤ 10 mol% LT, based on the combined results of temperaturevariable X-ray powder diffraction and dielectric measurements. In addition to the reported orthorhombic and tetragonal polymorphs of NKN-LT, a monoclinic phase is revealed. Changes to electrical properties as a function of LT substitution are correlated to phase content. Increasing the LT content from 5 to 7 mol% LT led to improved temperature stability of piezoelectric properties because of the avoidance of the monoclinic-tetragonal polymorphic phase transition during thermal cycling (at >25°C). For 7 mol% LT samples: d(33) = 200 pC/N; T(c) = 440°C; ε(r) = 550 and tan δ = 0.02 (at 20°C). Modification of this composition by solid solution with BiScO(3) led to a decrease in d(33) values. Transmission electron microscopy of a sample of 0.95[0.93 NKN-0.07LT]-0.05BiScO(3) indicated a core-shell grain structure which led to temperature-stable dielectric properties.
本文呈现了 Na(0.5)K(0.5)NbO(3)-LiTaO(3) 固溶体系列（NKN-LT）的相图，其组成部分 LT 的含量不超过 10 mol%，这是基于温度可变 X 射线粉末衍射和介电测量的综合结果。除了已报道的 NKN-LT 的正交相和四方相多晶型外，还揭示了一种单斜相。电性能随 LT 取代的变化与相含量有关。随着 LT 含量从 5 mol%增加到 7 mol%，由于在热循环过程中避免了单斜-四方多晶型相变，压电性能的温度稳定性得到了提高（高于 25°C）。对于 7 mol% LT 的样品：d(33) = 200 pC/N；T(c) = 440°C；ε(r) = 550 和 tan δ = 0.02（在 20°C 时）。通过与 BiScO(3) 的固溶改性，使得 d(33) 值降低。对 0.95[0.93 NKN-0.07LT]-0.05BiScO(3) 的样品进行透射电子显微镜观察，表明存在核壳晶粒结构，这导致了温度稳定的介电性能。
