CaBi2Nb2O9 (CBN)‐based high‐temperature piezoelectric ceramics with the formula of CaBi2Nb2−x(W3/4Cu1/4)xO9 were prepared via the traditional solid‐state reaction method. Both the bulk microstructure and the electrical performance of the W/Cu co‐doped CBN‐based ceramics were systematically investigated. The results indicated that the W/Cu incorporation into the Nb‐site altered the crystal structure, which enhanced the piezoelectricity and resistivity. The ceramic with the composition CaBi2Nb1.96(W3/4Cu1/4)0.04O9 exhibited good performance with a high d33 (~14 pC/N) and TC (~939℃). Moreover, the ceramic exhibited a good electrical resistivity (ρ) of 4.91 × 105 Ω·cm and a low dielectric loss (tanδ) of 0.1 at 600℃. Furthermore, the ceramic that was annealed at 900℃ for 2 h presented a d33 value of 13 pC/N, thus indicating good thermal stability of the piezoelectric properties. All these results confirm that the CaBi2Nb1.96(W3/4Cu1/4)0.04O9 ceramic may act as a potential promising candidate for piezoelectric device applications in high‐temperature environments.

It is well-known that the regulation of the phase boundary is an efficient strategy to boost the piezoelectric performance of perovskite structure ceramics. However, it is seldomly used in the bismuth-layered structure high-temperature piezoelectric ceramic research field because of the lack of an available morphotropic phase boundary (MPB). In this work, a pseudo-MPB was constructed by the dual introduction of Ce and Cr ions to the CBN ceramic, which remarkably optimized the piezoelectricity and ferroelectricity. Furthermore, the Ce and Cr ions evidently suppressed the oxygen vacancy concentration, leading to improvements in resistivity and thermal stability. Optimized performances with a satisfactory piezoelectric coefficient (d 33 ∼ 17 pC/N) and an elevated resistivity (ρ) of 1.35 × 105 Ω·cm (at 600 °C) were realized in the Ca0.97Ce0.03Bi2Nb1.985Cr0.015O9 ceramic, accompanied by a high Curie temperature (T C ∼ 934 °C) and good piezoelectric thermal stability. These results reveal that the Ca0.97Ce0.03Bi2Nb1.985Cr0.015O9 ceramic could be a prospective piezoelectric material for sensor applications at high temperatures. Moreover, this work provides a feasible strategy for optimizing the piezoelectric performances of the CBN-based ceramics by constructing the pseudo-MPB.

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The purpose of this paper is to provide a new method for solving the problem of the 3D source localization in indoor environments with weak airflow by the experimental study on the multi-robot method. For this purpose, we developed a 3D MRO (mobile robot olfaction) system consisting of three mobile robots. The gas sensor carried with each robot has a moving range of 0.5 m to 1.5 m on the Z-axis. A total of 60 experiments were conducted to validate and compare the standard whale optimization algorithm (SWOA) and the standard particle swarm optimization (SPSO) methods in a 7.65 m×4.1 m experimental area with two source heights (0.75 m and 1.05 m). For two source heights, the success rate and localization step of the SPSO method are 56.7% (17/30) and 31.4 steps, respectively. In addition, the success rate and localization step of the SWOA method are 80% (24/30) and 32.9 steps, respectively. These results show that the SWOA method has strong application potential in indoor environments with weak airflow.