Lecture Amir Abbas Haghighirad
|15 June 2012||FWN-Building 5118.-152, Nijenborgh 4, 9747 AG, Groningen|
|Speaker:||Dr. Amir Abbas Haghighirad|
|Affiliation:||Physikalisches Institut, Johann Wolfgang Goethe-Universitaet, Frankfurt am Main, Germany|
|Title:||Synthesis and growth of novel materials at extreme conditions of pressure and temperature|
|Date:||Fri Jun 15, 2012|
|Telephone:||+31 50 363 4419|
Crystal growth under high pressure offers chances to manufacture novel materials in high-purity single crystalline form to explore the physics of electrons subject to strongly competing interactions. In this regime of strong “frustration” the quantum nature of the electron spin and orbital motion become very important and can lead to completely new properties. Synthesizing materials in this regime is very challenging as often extreme conditions of high pressures and temperatures are required to stabilize a desired composition, ion valence or crystal structure, but it potentially can open up new avenues for synthesizing novel materials.
The multianvil technique is a very effective and flexible way which combines comparatively large sample volumes, high pressures and high temperatures.
With our current setup, pressures up to 7 GPa are reached in a sample volume (~ 80 mm3).
A small graphite tube serves as a resistance furnace for temperatures up to 1500 °C.
We have investigated the synthesis and crystal growth of pyrochlore vanadates A 2V2O7 ( A = Er, Y and Dy). The application of high pressure is necessary for the formation and stability of these compounds.
For the first time, A 2V2O7 ( A = Er, Y and Dy) single crystals were grown by using grain growth method at high pressure (HP) of 5.0-5.5 GPa and high temperatures (HT) of ~ 1200 °C in a 6-8 multianvil appartus.
Currently we study the preparation and crystal growth of the superconducting iron-based layered compounds, e.g. FeSe1-x and R FeAsO1-xFx ( R = La, Nd, Sm, etc.).
Despite the structural simplicity of FeSe among the Fe-based-compounds, crystal growth of this compound is very challenging taking into account the different polymorphs and the extreme sensitivity of superconductivity to small deviations depending on the elemental composition and synthesis conditions, temperature or pressure.
|Last modified:||22 October 2012 2.31 p.m.|