About Us
High Pressure Physics Section
The universe we live in is host to extreme conditions of pressure and temperature. The conditions in our immediate vicinity are known as ambient pressure (~1 bar) and temperature (few tens of degree celsius). The planet we live in itself has extreme conditions as one proceeds towards its centre. The pressure at the center of our earth is three and a half million times the atmospheric pressure and the temperature is about five thousand Kelvin. Still higher pressures and temperatures prevail at the centres of other planets. If we can simulate these conditions in a laboratory and investigate the behaviour of materials at such extreme conditions, we can throw more light on the formation and composition of our earth as well as other planets.
It is now possible to simulate these extreme conditions in a laboratory and investigate the behaviour of materials by using a facility called the Laser Heated Diamond Anvil Cell. High pressures of the order of five million atmosphere can be generated by squeezing the sample between a pair of diamond anvils in a Diamond Anvil Cell (DAC). Simultaneously, temperatures >5000K can be generated by focussing a high power infrared laser onto the pressurized sample. Further, the behaviour of the sample at such extreme conditions can be studied by a variety of techniques such as x-ray diffraction, micro-Raman, optical reflectivity and so on. This laboratory has the distinction of developing these facilities for the first time in our country.
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Schematic illustrates the principle of generating extreme conditions of pressure and temperature in the lab |
Indigenously developed Mao-Bell DAC capable of generating megabar pressure |
Diamond the hardest naturally occurring material known to man is formed in earths crust at high pressure and high temperatures. These conditions can be simulated quiet easily in the lab to carryout direct conversion of graphite to diamond. Graphite contained between diamond anvils at high pressure (0.17 megabar or 17 GPa) is laser heated (T~2000 K) to form micro crystallite diamonds.
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| Micro crystallites of diamond of size ~2 micro meter seen in SEM image. | Micro-Raman spectra shows diamond Raman peak at 1330 cm-1 riding on a diamond like carbon background |
During the last three decades, this laboratory has not only developed several advanced and state of the art experimental techniques, but also and carried out research in frontline areas, such as the investigation of the early actinide elements and their intermetallic compounds, lanthanide based intermetallic compounds, 3d transitions metals, metallic glasses, quasicrystals, Fullerenes, matlockite systems, rare-earth sesquioxides, pyrochlore systems, high temperature structural intermetallics, 316-stainless steel, Ni-based smart materials, etc. The investigation of the lanthanide and actinide (f-electron) based intermetallics remains the main theme research of the group, and has already culminated into three review articles. Apart from more than hundred research articles that have been published in various national and international journals, five Ph.D. theses have come out based on the investigations carried out so far. Apart from these experimental activities, electronic structure calculations as a function of reduced volume (pressure) have been done on a number of systems, mainly to understand and interpret the observed compressibility and structural behaviour in terms of their electronic structure.
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High Pressure XRD patterns of LaGa2 , BaFBr and Gd2Zr2O7 showing structural phase transitions
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