Superconductivity has been realized in films of La1-x Sr x NiO2. Here we report synthesis and characterization of polycrystalline samples of La1-x Sr x NiO3 and La1-x Sr x NiO2 (0 ≤ x ≤ 0.2). Magnetization and resistivity measurements reveal that La1-x Sr x NiO3 are paramagnetic metal and La1-x Sr x NiO2 exhibit an insulating behavior. Superconductivity is not detected in bulk samples of La1-x Sr x NiO2. The absence of superconductivity in bulk La1-x Sr x NiO2 may be due to the generation of hydroxide during reduction, a small amount of nickel impurity, or incomplete reduction of apical oxygen. The effect of interface in films of La1-x Sr x NiO2 may also play a role for superconductivity.

We report the synthesis and characterization of a Si-based ternary semiconductor Mg2Si2Te6, which exhibits a quasi-two-dimensional structure, where the trigonal Mg2Si2Te6 layers are separated by Mg ions. Ultraviolet-visible absorption spectroscopy and density functional theory calculations were performed to investigate the electronic structure. The experimentally determined direct band gap is 1.39 eV, consistent with the value of the density function theory calculations. Our results reveal that Mg2Si2Te6 is a direct gap semiconductor, which is a potential candidate for near-infrared optoelectronic devices.

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