Chapters authored
Correlation between Structure, Electrical, and Magnetic Properties of Some Alkali-Oxide Materials
In this chapter, the correlation between structure and electrical properties of Na2MP1.5As0.5O7 (MII = Co and Cu) are treated. The structural study shows that the cobalt and copper isotype materials can be crystallized in the tetragonal and monoclinic systems, respectively. The electrical study using impedance spectroscopy technique showed that these mixed diphosphate diarsenates are fast electrical conductors; however, the cobalt material exhibited more conductive property than the copper compound. In addition, the powder perovskite manganites La0.7M0.2M’0.1MnO3 (M = Sr, Ba and M’ = Na, Ag and K) have been prepared using the conventional solid-state reaction. The structural, magnetic, and magnetocaloric properties of these perovskite manganites compounds were studied extensively by means of X-ray powder diffraction (XRD) and magnetic measurements. These samples were crystallized in the distorted rhombohedral system with R3c space group. The variation of magnetization (M) vs. temperature (T) reveals that all compounds exhibit a second-order ferromagnetic to paramagnetic phase transition in the vicinity of the Curie temperature (TC). A maximum magnetic entropy change, ΔSMMax, of 4.07 J kg−1 K−1 around 345 K was obtained in La0.7Sr0.2Na0.1MnO3 sample upon a magnetic field change of 5 T. The ΔSMMax values of La0.7Ba0.2M’0.1MnO3 are smaller in magnitude compared to La0.7Sr0.2M’0.1MnO3 samples and occur at lower temperatures.
Part of the book: Alkaline Chemistry and Applications
The Cuprate Ln2CuO4 (Ln: Rare Earth): Synthesis, Crystallography, and Applications
This chapter is concerned with a study of undoped and doped cuprates of the general formula Ln2CuO4 (Ln = rare-earth metal) and Ln2–xMxCuO4±δ (Ln = rare earth and M = Sr, Ba, Ca, Ln’, Bi, and 3d metal). The crystal structures of the undoped and doped cuprates having the notations (T, T′, T*, S, and O), significantly depend, however, on the synthetic route. The topotactic synthesis is a specific method, which allows the transformation of the cuprate from the T to T′ structure. The importance of these materials originates from the discovery of the unconventional superconductors of the Ce-doped Ln2CuO4. The cuprate materials could function as insulators or semiconductors which are valuable tools in optoelectronic applications. The doped cuprate materials are good ionic conductors and are found useful as electrodes in fuel cell applications. The undoped cuprates reveal high dielectric properties.
Part of the book: Crystal Growth and Chirality