•Lead-free 0.89BNT–0.06BT–0.05KNN AFE ceramics were prepared by pressureless two-step sintering method.•The energy-storage density and AFE properties were significantly enhanced by two-step sintering method.•The ceramics by two-step sintering method had smaller grain size and more uniform microstructure than those of the ceramics by single-step sintering method.This work compared the effects of different sintering methods on the microstructure and anti-ferroelectric properties of lead-free 0.89Bi0.5Na0.5TiO3–0.06BaTiO3–0.05K0.5Na0.5NbO3 ternary system ceramics. The ceramics by two-step sintering method had smaller grain size and more uniform microstructure than those of the ceramics by single-step sintering method. The mechanism of grain growth in different sintering methods is discussed. The ceramics by two-step sintering method exhibited better anti-ferroelectricties than those of the ceramics by single-step sintering method. The polarization hysteresis (P–E) loop showed optimum electrical performances with a low remanent polarization (Pr=5.4 μC/cm2) and a coercive field (Ec=8.2 kV/cm), and the energy density (W) reached 0.90 J/cm3 at 10 Hz. The storage capacity is three times that of the single-step sintering ceramics.

Large-scale one-dimensional (1D) rod-like and octagonal-like KEu(MoO4)2 microcrystals were successfully synthesized by a simple, environmental friendly, and low cost molten salt method using halons (KCl or KBr) as flux. The as-prepared products were characterized by X-ray powder diffractometry (XRD), scanning electron microscopy (SEM), high resolution transmission electron microscopy (HRTEM), selected-area electron diffraction (SAED) and photoluminescence (PL) spectrometry. The results show that the reaction parameters, including reaction temperature and reaction time, played important roles on the phase structures and morphologies of the final products. The possible growth process of 1D rod-like KEu(MoO4)2 was proposed based on the time-dependent shape evolution and HRTEM analysis, which followed oriented aggregation and Ostwald ripening. The results of SAED and HRTEM investigations indicated an incommensurate modulated structure in the rod-like KEu(MoO4)2, and all the reflections can be expressed as ha* + kb* + lc* + mq, where m is an integer, and modulated vector q = 0.182b* + 0.156c*. Room temperature photoluminescence spectra of KEu(MoO4)2 microcrystals reveal a strong red emission via5D0 → 7F2 transition at 615 nm, and the 1D rod-like microcrystals own the enhanced intensity compared with the octagonal-like ones.

BaMoO4 with 3D hierarchical multilayer disk-like and nest-like architectures self-assembled from 2D nanosheets was successfully synthesized via a microwave-assisted hydrothermal route without any surfactant. The as-prepared products were characterized by X-ray powder diffractometer (XRD), scanning electron microscope (SEM), field emission transmission electron microscope (FE-TEM), and photoluminescence (PL) spectrometer. The results show that the reaction parameters, including pH value, reactant concentration, and molar ratio of [Ba2+]/[MoO42-], played important roles on the morphologies of the final products. And the formation mechanism of 3D hierarchical architectures is a stepwise oriented aggregation-based self-assembly process. The superstructure characteristic of 3D nest-like BaMoO4 architecture was observed in HRTEM image and the corresponding fast Fourier transform (FFT) for the first time, and the superlattice reflections with non-integer indices occurred around the subcell reflections at ±1/6(2a* + 2c*). Room temperature photoluminescence spectra of 3D BaMoO4 architectures reveal a strong and broad blue emission, and the 3D nest-like architectures own the enhanced intensity than multilayer disks.Graphical abstractHighlights► BaMoO4 hierarchical architectures have been synthesized by microwave heating route. ► 3D BaMoO4 nest-like architecture particles reveal a strong and broad blue emission. ► A stepwise oriented self-assembly mechanism was proposed. ► The superlattice reflection of 3D BaMoO4 nest-like architecture was observed firstly.

Uniform SrMoO4 micro-octahedrons were synthesized by microwave heating method. The as-prepared products were characterized by several techniques. Results showed that the reactant concentration and reaction time had crucial influence on the morphology of the products. The possible growth process of SrMoO4 octahedron was proposed based on the time-dependent shape evolution, which followed Ostwald ripening, crystallization/dissolution, and re-crystallization. Eu3 +-doped (1–20 mol%) SrMoO4 with octahedrons-like polyhedron was prepared under the same condition. The excitation spectrum of SrMoO4:Eu3 + was mainly composed of three intense peaks of 305, 393 and 463 nm. The characteristic red emission peaks at 612/615 nm were ascribed to 5D0 → 7F2 transition of Eu3 + ions. The quenching concentration was found at ~ 15 mol% doping of Eu3 +.Micro-sized SrMoO4 and SrMoO4:Eu3 + octahedrons were synthesized by a microwave heating method without adding surfactant. These octahedrons had uniform shape and narrow particle size distributions.Highlights► Eu3+ doped SrMoO4 micro-octahedrons were synthesized by microwave heating route. ► The growth conditions and formation mechanism were studied in detail. ► Luminescence property of SrMoO4:Eu3+ with different Eu3+-doping was discussed.