Influence of Bi nonstoichiometry on the energy storage properties of 0.93KNN–0.07BixMN relaxor ferroelectrics

Ceramic-based dielectric capacitors are becoming more and more important in electronic devices. The ceramics of 0.93K0.5Na0.5NbO3–0.07Bix(Mg1∕3Nb2∕3)O3 (0.93KNN–0.07BixMN) (x=0.60, 2/3, 0.75 and 0.95) were successfully fabricated by virtue of the solid reaction process in this work. The results showed that the amount of Bi content has a significant impact on the ceramics of 0.93KNN–0.07BixMN. XRD indicates that all specimens exhibit a pure perovskite structure and existing oxygen vacancy in the specimens. The mean grain size for all specimens belong to submicron scale, and the sample of x=0.95 owns the smallest grain size is 0.11μm. The maximum dielectric constant increases but the phase transition temperature Tm exhibits a contrary tendency at 1MHz with increasing Bi concentration. Besides, all ceramics are relaxor ferroelectric. The impedance analysis further revealed that the activation energy of the ceramics increases with Bi content. Eventually, the highest η of 58.8% and Wrec of 1.30J/cm3 are simultaneously achieved in the sample with x=0.60. Overall, we demonstrate in this work that stoichiometry control of Bi in 0.93KNN–0.07BixMN ceramics is a practical method to obtain the desired structural, dielectric and energy storage properties

20-mm-Large Single-Crystalline Formamidinium-Perovskite Wafer for Mass Production of Integrated Photodetectors

CH3NH3PbX3 (MAPbX(3))-based perovskite has attracted tremendous research efforts in the last few years. With the discovery that the HC(NH2) 2PbI3 (FAPbI(3)) perovskite offers even higher solar cell efficiency, better thermal stability, and broader optical absorption, it is expected that it will provide more excitement in optoelectronic applications including laser, LED, photodetector, etc. The development in preparing large Single-Crystalline Formamidinium-Perovskite FAPbI(3) using the inverse-temperature reactive crystallization process, and associated wafer-slicing process is presented. The availability of the large Single-Crystalline Formamidinium-Perovskite Wafer makes it possible to fabricate integrated circuits. An array of 153 photodetectors on a piece of thin wafer, demonstrating feasibility of mass production of integrated circuits on the perovskite wafer is designed and prepared. It is found that the wafer-based photodetector shows much superior performance, with 90 times higher photoresponse and broader optical absorption than its thin-film perovskite counterpart

Ultra-fast charge-discharge and high-energy storage performance realized in KNaNbO3-Bi(MnNi)O3 ceramics

Lead-free relaxor ceramics (1 − [Formula: see text])K[Formula: see text]Na[Formula: see text]NbO3 − [Formula: see text]Bi(Mn[Formula: see text]Ni[Formula: see text])O3 ((1 − [Formula: see text] )KNN- [Formula: see text]BMN) with considerable charge–discharge characteristics and energy storage properties were prepared by a solid state method. Remarkable, a BMN doping level of 0.04, 0.96KNN–0.04BMN ceramic obtained good energy storage performance with acceptable energy storage density [Formula: see text][Formula: see text] of 1.826 J/cm3 and energy storage efficiency [Formula: see text] of 77.4%, as well as good frequency stability (1–500 Hz) and fatigue resistance (1–5000 cycles). Meanwhile, a satisfactory charge–discharge performance with power density [Formula: see text][Formula: see text] [Formula: see text] 98.90 MW/cm3, discharge time [Formula: see text][Formula: see text] < 70 ns and temperature stability (30–180∘C) was obtained in 0.96KNN–0.04BMN ceramic. The small grain size ([Formula: see text]150 nm) and the high polarizability of Bi[Formula: see text] are directly related to its good energy storage capacity. This work proposes a feasible approach for lead-free KNN-based ceramics to achieve high-energy storage and ultra-fast charge–discharge performance as well as candidate materials for the application of advanced high-temperature pulse capacitors

Contrasting roles of Bi-doping and Bi 2 Te 3 alloying on the thermoelectric performance of SnTe

Previous studies have revealed that both Bi doping and Bi2Te3 alloying are successful strategies to optimize the thermoelectric performance of SnTe; however, detailed and thorough investigations on exactly how they differ in modulating the band structure and microstructure were seldom given. Through a systematic comparison between Bi-doped and Bi2Te3-alloyed SnTe, we find in this work that despite the fact that they both contribute to the valence band convergence of SnTe, Bi2Te3 alloying induces little effect on the hole concentration unlike the typical n-type feature of Bi-doping; moreover, Bi2Te3 alloying tends to produce dense dislocation arrays at micron-scale grain boundaries which differs significantly from the substitutional point defect character upon Bi-doping. It was then found that Bi2Te3 alloying exhibits a relatively higher quality factor (B ∼ μw/κlat) at higher temperatures than Bi-doping. Subsequent Ge-doping in Bi2Te3-alloyed samples results in further valence band convergence and hole concentration optimization and eventually results in a maximum figure of merit ZT of 1.4 at 873 K in the composition of (Sn0.88Ge0.12Te)0.97-(BiTe1.5)0.03

A Strategy for the Synthesis of Oxonitridosilicate Phosphors from Anionic Condensation

The exploration of new luminescent materials is driven by potential applications in solid-state lighting and display technologies. In this paper, we employed an anionic condensation approach to craft novel oxonitridosilicate compounds by substituting 3O2– with 2N3– in a carefully selected system. This approach enabled us to synthesize a highly condensed oxonitridosilicate compound LaSr4Si5N9O2, which crystallizes in the orthorhombic crystal system with the space group Ama2 (no. 40) and lattice parameters a = 9.2986(1) Å, b = 23.4382(1) Å, c = 5.371(1) Å, V = 1170.55(1) Å3, and Z = 4. The condensation appears inside the layer, with dreier rings originating from neighboring tetrahedra connected by bridging nitride (N[2]). This enriches the possibility of using the approach to design multiple layered or other featured oxonitridosilicates. Furthermore, we investigated the luminescence properties when doped with rare-earth ions. The Pr3+-doped LaSr4Si5N9O2 exhibits a remarkably narrow-band red emission (λem ≈ 618 nm, fwhm ≈ 54 nm) when excited by UV and blue light