A2AgCrCl6 (A = Li, Na, K, Rb, Cs) halide double perovskites: a transition metal-based semiconducting material series with appreciable optical characteristics

The theoretical examination of the geometric, energetic, phonon and optoelectronic properties of cubic and hexagonal A2AgCrCl6 (A = Cs, Rb, K, Na, Li) using meta-GGA SCAN-rVV10 has led us to identify cubic Cs2AgCrCl6 and Rb2AgCrCl6 as two dynamically stable double perovskites, with impressive optical features.

Machinablity improvement with ultrasonic vibration–assisted micro-milling

An ultrasonic vibration–assisted micro-milling with horizontal vibration of workpiece is investigated in this article. A vibration platform with maximum amplitude of 15 μm based on universal ball support structure is designed and built by our group. Titanium alloy TC4 and aluminum alloy 6061T6 were chosen as workpiece material. Series of slot-milling experiments were conducted with and without vibration at different amplitudes and feed rates to explore the effects of vibration on the micro-milling. Experiment results showed that ultrasonic vibration can effectively reduce milling force by 12% and 17%, respectively, for aluminum alloy 6061T6 and titanium alloy TC4 compared with that of conventional milling and hence leading to a better machining accuracy and longer tool life. Furthermore, the effect of ultrasonic vibration on titanium alloy is much more obvious. The topographies of machined surfaces also showed that ultrasonic vibration can reduce surface defects and machining marks and thus improve the surface quality for both 6061T6 and TC4. Besides these, it is worth to be noted that ultrasonic vibration leads the size effect point appear at much lower feed rate than conventional milling, which means vibration brings a change to machining mechanism and delays the appearance of micro-milling.

INFLUENCE OF SAMARIUM SUBSTITUTION ON DIELECTRIC PROPERTIES OF BARIUM TITANATE BASED CERAMICS

In this paper we report samarium substituted Ba 0.80 Pb 0.20 Ti 0.90 Zr 0.10 O 3 (BPZT) ceramics. The material series with compositional formula Ba 0.80-x Sm x Pb 0.20 Ti 0.90 Zr 0.10 O 3 with x varying from 0 to 0.01 in the steps of 0.0025 was chosen for investigations. The material was synthesized by solid state reaction method. Reacted powders compacted in the form of circular discs were sintered at 1325°C. All the samples were subjected to X-ray analysis and found to be single phase. Dielectric behavior was studied as a function of frequency and temperature and Curie temperature (Tc) was determined. Tc was found to decrease with increasing x. The details are discussed and presented here.

STRUCTURAL AND MAGNETIC PROPERTIES OF Y1-xZrxBa2Cu3O7-δ SUPERCONDUCTING COMPOUNDS

The high-T c Y 1-x Zr x Ba 2 Cu 3 O 7-δ superconductive ceramic material series with x = 0.01, 0.05 and 0.10 was sintered. The system was investigated from the structural and magnetic points of view. The room temperature X-ray pattern shows only orthorhombic reflection and unreacted zirconium oxide reflection. The temperature dependence of the magnetic susceptibility between liquid nitrogen and room temperature reflects a diamagnetic superconductive transition. The zirconium presence in the superconducting compounds determined the approximate linear increase of the critical temperature. The sintering temperature increase between 1200 and 1260 K lowers monotonously the critical temperature between 112 and 91.5 K.

Lithium Intercalation in Oxides: EMF Related to Structure and Chemistry

Experimental results for a number of oxide host materials as electrodes in lithium batteries are compared in order to obtain a better understanding of the factors influencing the emf-composition relationships. These factors are divided into two main groups: Those that are consequences of the structure of the host lattice, and those who follow from the chemistry of the host material. Series of materials with the same structure, but different chemical composition (spinels and MO2(B)) are compared, as well as series of materials with the same chemical composition, LixV2O5, but different structure. These data show that the potential level is mainly determined by the host chemistry, although destabilisation of the host can also give a significant contribution. The host structure will determine the width of the composition interval as well as the inflexions on the emf-curve. The possibility for tailoring the emf by using mixtures of transition metals in the host lattice is discussed.