Search

Bi‐Zn‐Nb‐O‐based microwave dielectric ceramics are promising candidates for wireless communication. Investigations have concentrated on their fabrication methods and doping modification. In this work, the densification mechanism and grain growth kinetics of the Bi‐Zn‐Nb‐O‐based microwave dielectric ceramics were explored. A significantly wide sintering temperature window (800–1000°C) of the monoclinic Bi2Zn2/3Nb4/3O7 (BZN) was found. High‐density stacking faults were observed in BZN grains at the initial stage of sintering, which could act as paths for mass transport, thus remarkably accelerating the densification process and decreasing the densification temperature. On the other hand, BZN possesses a high grain growth exponent and activation energy, which indicates a slow grain growth rate and a high threshold for abnormal grain growth, corresponding to the wide sintering temperature window. Moreover, the BZN ceramics display good microwave dielectric properties stability over a wide temperature range (25–450°C). [ABSTRACT FROM AUTHOR]

TeO2 single crystal has drawn much attention in recent years due to its excellent acousto‐optic (AO) performance in the field of spectral imaging and optical processing. The optical properties of TeO2 single crystal are critical for the fabrication of AO devices. To improve the optical properties of the TeO2 single crystal, Mn4+ ions were doped into the TeO2 lattice. Herein, bulk TeO2 single crystal and TeO2:0.02Mn4+ single crystal have been successfully grown by a Bridgman method. Compared with the TeO2 single crystal, a 30% transmittance increase was observed in the TeO2:0.02Mn4+ single crystal. Furthermore, the TeO2:0.02Mn4+ single crystal shows a smaller extinction coefficient (≤0.01) in the Vis–NIR region, indicating less optical loss. The bandgap energy of TeO2:0.02Mn4+ was broadened from 3.360 to 3.635 eV. In addition, TeO2:0.02Mn4+ single crystal exhibits a higher refractive index (about 2.244), which indicates that TeO2:0.02Mn4+ single crystal is a potential medium for high‐efficiency AO devices. [ABSTRACT FROM AUTHOR]

SrTiO3‐modified lead‐free piezoelectric ceramics, (0.93‐x)Bi0.5Na0.5TiO3‐xSrTiO3‐0.06BaTiO3‐0.01 K0.5Na0.5NbO3 [(BNT‐xST)‐BT‐KNN, x = 0‐0.06], were prepared using a conventional solid‐state reaction method. The XRD structure analysis and electric properties characteristics revealed the ST‐induced phase transformation from the ferroelectric phase to the relaxor phase and their coexistence state. Benefiting from the ST‐destructed ferroelectric long‐range orders, the high normalized strain value of 600 pm/V was obtained in the (BNT‐0.02ST)‐BT‐KNN ceramic at 5 kV/mm. The ST‐generated relaxor phase was found to have a constructive effect on improving the temperature stability and restraining the hysteresis of the electric‐field‐induced strain. The normalized strain of (BNT‐0.06ST)‐BT‐KNN ceramics could be kept at a high value ~337 pm/V at elevated temperature up to 120°C. [ABSTRACT FROM AUTHOR]

Ca and Ta co‐doped AgNbO3 antiferroelectric lead‐free ceramics were fabricated by rolling process technique, and improved energy storage properties were obtained. X‐ray diffraction and Raman spectra indicate a single perovskite structure for (Ag1‐2xCax)(Nb1‐xTax)O3 ceramics. The dielectric performances were also investigated, showing that increasing the content of Ca and Ta from 0.1 to 5 mol% gradually decreased the temperatures of the phase transition of monoclinic M1‐M2 and M2‐M3. This proved the enhanced antiferroelectricity stability associated with the enlarged low temperature phase transition region. The obtained (Ag0.90Ca0.05)(Nb0.95Ta0.05)O3 ceramics exhibit an enhanced recoverable energy storage density (3.36 J/cm3) and efficiency (58.3%) with good temperature and frequency stability. The same composition shows excellent charge and discharge properties with a discharge current as high as 91.5 A and fast discharge speed (150 ns discharge period). All these merits demonstrate that AgNbO3‐based antiferroelectric ceramics are competitive with other lead‐based and lead‐free dielectric capacitors, which are promising candidates for dielectric energy storage applications. [ABSTRACT FROM AUTHOR]