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Plate-like single-crystalline BaBi₄Ti₄${\text{O}}_{15}$ particles were synthesized by the molten salt synthesis (MSS) method. The effects of sintering temperature, holding time, and NaCl–KCl molten salt content on the phase structure and morphology of plate-like BaBi₄-Ti₄${\text{O}}_{15}$ particles were investigated. The results show that plate-like BaBi₄Ti₄${\text{O}}_{15}$ particles can be synthesized when the sintering temperature is above 800${}^{\circ }$C. The size of particles increases with increasing sintering temperature and molten salt content. Largely anisotropic plate-like BaBi₄Ti₄${\text{O}}_{15}$ particles with diameter $\ge$10$\mu$m and thickness of $\sim$0.3 $\mu$m can be obtained under the optimum process parameters. The crystal structure of BaBi₄Ti₄${\text{O}}_{15}$ was determined as A2₁am by TEM, which should be attributed to the Bi${}^{3+}$ and Ba${}^{2+}$ diffusing into [TiO₆] octahedrons.

A high performance of novel three-component composites with 2–1–2 connectivity is reported and discussed. Layers of the composites are parallel-connected, and each layer contains the ferroelectric (FE) component. The layer of the first type (LFT) represents domain-engineered single crystal poled along either [0 0 1] or [0 1 1]. The layer of the second type is described as a system of long FE ceramic rods that have the shape of an elliptic cylinder and are aligned in a polymer medium. Piezoelectric coefficients $d_{3j}^{\ast }$ and $g_{3j}^{\ast }$ and sets of figures of merit (FOM) (energy-harvesting $d_{3j}^{\ast }{g}_{3j}^{\ast }$, modified $F_{3j}^{\ast \sigma }$ for a stress-driven harvester and modified $F_{3j}^{\ast \xi }$ for a strain-driven harvester) are analyzed to show their large values and specifics of the anisotropy when varying volume fractions of components and a rotation angle of the ceramic rod bases. For the first time, the studied parameters are compared in two directions: (i) the composite based on [0 0 1]-poled single crystal versus the composite based on [0 1 1]-poled single crystal and (ii) the lead-free composite versus the lead-containing composite (both based on [0 0 1]-poled single crystals). The advantages of the high-performance lead-free composite are discussed. The 2–1–2 composites put forward in this paper are of interest as advanced materials suitable for piezoelectric sensors, actuators and energy-harvesting systems operating at constant stress or strain.