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Ferroelectric Sr1−xBaxBi2(Nb0.5Ta0.5)2O9 and Sr0.5Ba0.5Bi2(Nb1−yTay)2O9 were synthesized by solid state reaction route. X-ray diffraction studies confirm the formation of single phase layered perovskite solid solutions over a wide range of compositions (x=y=0.0, 0.25, 0.50, 0.75 and 1). The lattice parameters and the Curie temperature (Tc) have been found to have linear dependence on x and y. Transmission electron microscopy (TEM) suggest the lowering of orthorhombic distortion with increasing Ba2+ substitution. Variations in microstructural features as a function of x and y were monitored by scanning electron microscopy (SEM). The dielectric constant at room temperature increases with increase in both x and y. Interestingly Ba2+ substitution on Sr2+ site induces diffused phase transition and diffuseness increases with increasing Ba2+ concentration. [Copyright &y& Elsevier]

Abstract: Microstructures of 76Mo–14Si–10B, 77Mo–12Si–8B–3Al, and 73.4Mo–11.2Si–8.1B–7.3Al alloys, processed by reaction hot pressing of elemental powder mixtures, have shown α-Mo, Mo3Si, and Mo5SiB2 phases. In addition, particles of SiO2 formed from the oxygen content of raw materials could be seen in the 76Mo–14Si–10B alloy, while α-Al2O3 formed in the alloys containing Al. Parts of the Al have been found within the solid solutions of α-Mo and Mo3Si. The average fracture toughness determined from indentation crack lengths and three-point bend testing of single edge notch bend specimens lies in the range of 5.0–8.7MPa√m, with alloys containing Al demonstrating higher values. Analyses of load-displacement plots, fracture profiles and indentation crack paths have shown evidence of R-curve type behaviour and operating toughening mechanisms involving crack bridging by α-Mo, crack deflection and branching. Flexural strength is related to volume fraction of the α-Mo and Al content. Compression tests on the 76Mo–14Si–10B alloy between 1100°C and 1350°C have shown excellent strength retention, and evidence of thermally activated plastic flow. [Copyright &y& Elsevier]