Excellent Room-temperature Properties Research Articles

Flash sintering BaTiO3-0.01MgO-0.01Nb2O5-xBi2O3 ceramics with superior dielectric temperature stability via defect engineering

In this paper, Bi2O3 doped BaTiO3-0.01MgO-0.01Nb2O5 ceramics are designed to increase dielectric constant, reduce dielectric loss and improve temperature dielectric stability through inducing defects, and are prepared by flash sintering method to inhibit the volatilization of Bi element and ensure the element ratio. The microstructure, polarization mechanisms, dielectric properties and conduction mechanism of the ceramics are studied. The doping of Bi2O3 can enhance the relaxation behavior and dielectric properties. The defects evolution in BaTiO3-0.01MgO-0.01Nb2O-0.01Bi2O3 ceramics are studied. The results show that the BaTiO3 ceramics doped with different amounts of Bi2O3 can form defect dipoles {[BiBa∙‐MgTi″‐BiBa∙]×, [NbTi∙‐VBa″‐NbTi∙]×, [MgTi″‐VO∙∙]×} and oxygen vacancy, which enhance the short-range transition within the grain and inhibit the movement of free electrons at the grain boundary. The ceramics have excellent room temperature properties, high dielectric constant (εr = 2894) and low dielectric loss (tanδ < 0.03). The ceramics have superior temperature stability and satisfying the EIA X8R (Δεr/ε25 ≤ ±15 %, over the temperature range from −55 °C to 150 °C). It is found that flash sintering can effectively guarantee the stoichiometric concentration of bismuth element and obtain good properties of ceramics. This study demonstrates the potential of Bi2O3 doped BaTiO3-based ceramics synthetized by flash sintering as high-performance electronic device materials.

Enhancing the thermoelectric properties of bismuth antimony tellurides containing excess Te with respect to sintering temperature

Bi–Te-based thermoelectric materials with excellent room-temperature properties are difficult to commercialise because of their low dimensionless figure of merit ( ZT). In this study, a powder was synthesised by adding an excess amount of Te to improve its thermoelectric performance at room temperature. The synthesised powder was sintered using spark plasma sintering at various temperatures to examine the effect of temperature-dependent behaviour of Te on the electrical resistivity and Seebeck coefficient. The excess Te-containing powder exhibited excellent electrical conductivity and Seebeck coefficient at high temperatures, and the thermal conductivity was significantly reduced. Bi0.4Sb1.6Te3+ x ( x = 2) showed a maximum room-temperature ZT of 1.57 at a sintering temperature of 450°C.

Ancient and Modern Steels and Laminated Composites Containing Steels

AbstractA class of steels (ultrahigh-carbon steels, or UHCSs) containing high levels of carbon (i.e., ∼1–2 wt%) were originally developed for their superplastic characteristics. In combination with excellent room-temperature properties, the steels were developed for their commercial potential starting in the mid-1970s and continuing to the present time. The compositional similarities between these modern steels and ancient Damascus steels led to a revisiting of the history and metallurgy of Damascus and related steels. Also, as part of the development of UHCSs, modern laminated composites containing them have been designed and manufactured that have unique toughness characteristics. These laminated composites also have similarities to a range of laminated materials of historical interest. Finally, some comments are made on the utility of radiocarbon dating to determine the age of ancient irons and steels. Ten sidebars supplement this article as Web Extras on the MRS Bulletin Web site at www.mrs.org/publications/bulletin/2002/dec/.

ELEKTRON ZT1

Abstract ELEKTRON ZT1 is distinguished by the best combination of properties at temperatures of and above 600 F of any magnesium casting alloy; also by excellent room temperature properties, by freedom from microporosity, and exceptionally good founding characteristics. Very suitable for jet engine parts. This datasheet provides information on composition, physical properties, hardness, elasticity, and tensile properties as well as creep and fatigue. It also includes information on corrosion resistance as well as casting, heat treating, machining, and surface treatment. Filing Code: Mg-4. Producer or source: Aluminum Laboratories Ltd.