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SUMMARY:Synthesis and growth of novel materials at extreme conditions of p
 ressure and temperature
DTSTART:20121127T111500
DTSTAMP:20260916T043951Z
UID:eb316cc46f02c2add9783d78153187830517177bb658c653e91fefd9
CATEGORIES:Conferences - Seminars
DESCRIPTION:Dr. Amir Abbas Haghighirad\, Physikalisches Institut\, Goethe 
 University\, Frankfurt am Main\, Germany\nCrystal growth under high pressu
 re offers chances to manufacture novel materials in high-purity single cry
 stalline form to explore the physics of electrons subject to strongly comp
 eting 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 regi
 me is very challenging as often extreme conditions of high pressures and t
 emperatures are required to stabilize a desired composition\, ion valence 
 or crystal structure\, but it potentially can open up new avenues for synt
 hesizing novel materials. The multianvil technique is a very effective and
  flexible way which combines comparatively large sample volumes\, high pre
 ssures and high temperatures. With our current setup\, pressures up to 8 G
 Pa 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 investig
 ated the synthesis and crystal growth of pyrochlore vanadates A2V2O7 (A = 
 Er\, Ho\, Dy and Y). The application of high pressure is necessary for the
  formation and stability of these compounds.\nFor the first time\, A2V2O7 
 (A = Er\, Ho\, Dy and Y) 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.\nCurrently we study the preparati
 on and crystal growth of the superconducting iron-based layered compounds\
 , e.g. 11-compound FeSe1-x and the 1111-system LaFePnO1-xFx (Pn = P\, As\,
  Sb). Despite the structural simplicity of FeSe among the Fe-based-compoun
 ds\, crystal growth of this compound is very challenging taking into accou
 nt the different polymorphs and the extreme sensitivity of superconductivi
 ty to small deviations depending on the elemental composition and synthesi
 s conditions\, temperature or pressure. I will discuss different aspects o
 f high pressure technique and its impact in solid-state physics.
LOCATION:PH L1 503 http://plan.epfl.ch/?room=PHL1503
STATUS:CONFIRMED
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