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Dielectric tunability is widely used in numerous electronic devices, including wavelet filters, lens antennae, and varactors. However, a dielectric device often has only one tunable dielectric constant range, confining the integration of a multi‐frequency electronic circuit. Herein, a new kind of dielectric tunable textured BaTi0.99Fe0.01O3−δ ceramics with micro‐twin boundaries is proposed for the dual‐channel controllable dielectric constants. The relative tunability with the acceptable figure of merit is as large as 76% in the crossover channel, which is superior to that of the most state‐of‐the‐art BaxSr1 −xTiO3 counterparts. This new design strategy offers the possibility of dual‐channel filters in one dielectric device controlled by external electric fields. The required external electric field is moderate with the help of reversible micro twins, which is confirmed by first‐principles studies. The static magnetic field interference on the dielectric constant is also evaluated, showing the frequency stability of dielectric tunability in a range between 5k and 1 m Hz. [ABSTRACT FROM AUTHOR]

Single crystals of 2-methylbenzimidazolium perchlorate were prepared for the first time with a slow evaporation method from an aqueous solution of a mixture of 2-methylbenzimidazole (MBI) crystals and perchloric acid HClO4. The crystal structure was determined by single crystal X-ray diffraction (XRD) and confirmed by XRD of powder. Angle-resolved polarized Raman and Fourier-transform infrared (FTIR) absorption spectra of crystals consist of lines caused by molecular vibrations in MBI molecule and ClO4− tetrahedron in the region ν = 200–3500 cm−1 and lattice vibrations in the region of 0–200 cm−1. Both XRD and Raman spectroscopy show a protonation of MBI molecule in the crystal. An analysis of ultraviolet-visible (UV-Vis) absorption spectra gives an estimation of an optical gap Eg~3.9 eV in the crystals studied. Photoluminescence spectra of MBI-perchlorate crystals consist of a number of overlapping bands with the main maximum at Ephoton ≅ 2.0 eV. Thermogravimetry-differential scanning calorimetry (TG-DSC) revealed the presence of two first-order phase transitions with different temperature hysteresis at temperatures above room temperature. The higher temperature transition corresponds to the melting temperature. Both phase transitions are accompanied by a strong increase in the permittivity and conductivity, especially during melting, which is similar to the effect of an ionic liquid. [ABSTRACT FROM AUTHOR]

The existence of Bi-fluctuation dispersing in Na0.5Bi0.5TiO3 (NBT) relaxor ferroelectric is hinted in other recent studies. However, this fluctuation has not been directly observed yet. We introduce the Bi-rich nano-regions with different sizes in a series of NBT ceramics by the slight excess of Bi3+ content. The crystal symmetries of the Bi-rich nano-regions and the NBT matrix are rhombohedral. The lattice parameters of the nano-regions are larger than those of the matrix in NBT ceramics, which were confirmed by the X-ray diffraction Rietveld refinement, TEM techniques and first-principles calculation. Also, the disorder-induced nano-regions appearing as Bi-fluctuation are associated with the complex phase transitions and the high-frequency relaxor behaviour of NBT suggested by the dielectric measurements and Raman spectra. [ABSTRACT FROM AUTHOR]

Phase-pure Aurivillius BiTiFeO nanoparticles were successfully prepared using a sol-gel method. Behaviours of crystallisation were characterised by XRD, DTA, FT-IR, Raman spectra and HRTEM. Mass spectrum was used to monitor the combustion products of all organics in the xerogel during calcination. An intermediate product, BiOCO, which blocks the generation of the pyrochlore phases, was confirmed by XRD patterns and IR spectra. Calculated by XRD data using the Debye-Scherrer method, the average grain size in powders calcinated at 500 °C was 17.7 nm and grew to 80.5 nm at 850 °C. The local symmetry connected to FeO octahedral was broken. The XRD refinement and XPS analyses inferred the valence increase of ferric ions. The maximum magnetisation of nanoparticles prepared at 850 °C was 4.2 emu/g. The field cooling (FC) and zero field cooling (ZFC) tests showed a wide range of the blocking temperature ( T ) around 8-45 K answering for the lack of hump corresponding to the transition from superparamagnetism to blocking state. Graphical Abstract: [ABSTRACT FROM AUTHOR]