No abstract

Experimental data on the phase relations in the Cu, In, Se system are presented and the growth of single crystals of CuInSe2 from the melt is described. Hall measurements on both n- and p-type crystals reveal that impurity conduction dominates the low-temperature transport properties. Type conversion by annealing of initially n-type crystals in excess selenium vapor leads to a substantial increase in the compensation level.

Polycrystalline Ca 2 Fe 2Àx Al x O 5 (x = 0-1.4) samples were prepared by conventional solid-state reactions. Their crystalline/electronic structures and magnetic properties were characterized in detail. Powder X-ray diffraction analyses revealed that the samples crystallized in orthorhombic brownmillerite-type structures with the occurrence of the Pcmn-Ibm2 phase separation in the region between x = 0.4 and 0.6. The results obtained from analyzing Raman scattering and X-ray-absorption fine-structure spectra also indicated this phase separation. Although x in Ca 2 Fe 2Àx Al x O 5 varies in a wide range from 0 to 1.4, the +3 oxidation state of Fe remained almost unchanged. Magnetization measurements revealed that all Ca 2 Fe 2Àx Al x O 5 samples have weak ferromagnetic order, and both the saturation magnetization and coercive force are dependent on the temperature, x, and structure phases.

Three-dimensional covalent organic frameworks possess hierarchical nanopores, enormous surface areas with high porosity, and open positions. The synthesis of large crystals of three-dimensional covalent organic frameworks is a challenge, since different structures are generated during the synthesis. Presently, their synthesis with new topologies for promising applications has been developed by the use of building units with varied geometries. Covalent organic frameworks have multiple applications: chemical sensing, fabrication of electronic devices, heterogeneous catalysts, etc. We have presented the techniques for the synthesis of three-dimensional covalent organic frameworks, their properties, and their potential applications in this review.

No abstract