Materials Synthesis, Crystal Growth and Characterization
Travelling Solvent Floating Zone (TSFZ) using an Optical Furnace
Examples of Crystal Growth
Complex copper oxides (cuprates) with magnetic copper cations (spin ½) creating quasi-one-dimensional patterns in the structure are model systems for quantum magnetism science. A spin ladder can be considered as a chain of antiferromagnetically coupled pairs of spins creating spin dimmers. BiCu2PO6 is a new model compound containing such zigzag copper chains (see Figure 3)
Sr14-xCaxCu24O41 is the only superconducting cuprate containing in the structure only one-dimensional spin ladders (Cu2O3) and chains (CuO) but no typical superconducting copper oxide layers (CuO2).
For the first time superconductivity with TC≈12 K was observed for highly Ca-doped samples (x≈13.6) under high hydrostatic pressure of 3-4.5GPa. Crystals with Ca-content x≥12 can be grown by TSFZ method under high oxygen pressure. We have modified the mirror furnace to provide a stable crystal growth at oxygen pressure up to 35bar.
Other Examples of Crystals Grown by the TSFZ Method
Examples of Crystals Grown
Among the iron-based superconductors discovered in 2008, chalcogenides e.g. FeSe have the simplest layered structure in which Fe cations are tetrahedrally coordinated by Se. The superconducting transition temperature (Tc) of only 8K can be increased to over 30K by intercalation of alkali metals between the FeSe layers. Single crystals were grown in double wall evacuated silica ampoules in vapor of alkali metals (K, Rb, Cs) using FeSe as a precursor. The ampoules were annealed at 1030°C and then cooled down with the rate of 6°C/h.
High-Temperature Solution (Flux) Crystal GrowthThe flux method is the crystal growth from high-temperature solutions. The spontaneous crystallization occurs during slow cooling of the solution. Very often it is difficult to separate the crystals from the solvent as well as to avoid contaminations from the crucible material and the solvent. By this method crystal growth commonly occurs at temperature lower than the melting point of the material. This is crucial when the material:
- melt incongruently;
- undergoes a phase transition du ring cooling;
- has very high vapor pressure at a melting point
Examples of Crystals Grown by the Flux Method
Other Synthesis Methods
Structural Characterization: Laue X-Ray DiffractionThe Laue method is used to determine orientation and quality of single crystals. White (polychromatic) x-ray radiation is transmitted through a crystal. Each set of planes in the crystal structure diffracts the particular wavelength from the white radiation that satisfies the Bragg law. The diffracted beams form arrays of spots recorded by the CCD camera. Details of Laue setup can be found here.
Structural Characterization: Powder X-Ray Diffraction
- Phase identification
- Crystal structure determination
- Determine size and strain broadening