Pure K_0.5Na_0.5NbO₃ (KNN) and KNN doped with Li⁺ (6% mole), La³⁺(1.66%, 5%, 6% mole), and Ti⁴⁺ (10% mole) were prepared by mixture of oxides using high-energy milling and conventional solid-state reaction. The effects of the dopant on the physical properties of pure KNN have been evaluated based on the structural, ferroelectric, pyroelectric, and dielectric measurements. The XRD measurements show that KNN pure sample contains a mixture of monoclinic and orthorhombic crystalline phases, with a slightly higher concentration of monoclinic phase. In contrast, all doped samples show a higher concentration of the orthorhombic phase, as well as the presence of a secondary phase (K₆Nb_10.8O₃₀), also detected by Raman measurements. The samples with a higher concentration of this secondary phase, also present greater dielectric losses and lower values of remnant polarization. The dielectric measurements allowed us to detect temperatures of structural transitions (orthorhombic-tetragonal, O-T) previous to the ferroelectric-paraelectric transition (tetragonal-cubic, T-C), and also in this set of samples, a direct correlation was found between the values of remnant polarization and the corresponding pyroelectric signal response.

中文翻译：

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Li +，La 3+和Ti 4+掺杂的K 0.5 Na 0.5 NbO 3体系的结构，铁电，介电和热电性质的研究

通过混合制备纯K _0.5 Na _0.5 NbO ₃（KNN）和掺杂有Li ⁺（6％摩尔），La ³⁺（1.66％，5％，6％摩尔）和Ti ⁴⁺（10％摩尔）的KNN使用高能研磨和常规固态反应制备氧化物。已根据结构，铁电，热电和介电测量值评估了掺杂剂对纯KNN物理性能的影响。XRD测量表明，KNN纯样品包含单斜晶相和正交晶相的混合物，单斜晶相的浓度略高。相反，所有掺杂样品均显示出较高的正交晶相浓度，以及第二相的存在（K₆ Nb _10.8 O ₃₀），也通过拉曼测量法检测到。具有较高浓度的该第二相的样品也呈现出更大的介电损耗和更低的残余极化值。介电测量使我们能够检测到铁电-顺电转变（四方立方，TC）之前的结构转变（斜方四边形，OT）的温度，并且在这组样本中，还发现了剩余极化和相应的热释电信号响应。