High Pressure In Diamond Anvil Cell Research Articles

Tensorial stress-plastic strain fields in α - ω Zr mixture, transformation kinetics, and friction in diamond-anvil cell

Various phenomena (phase transformations (PTs), chemical reactions, microstructure evolution, strength, and friction) under high pressures in diamond-anvil cell are strongly affected by fields of stress and plastic strain tensors. However, they could not be measured. Here, we suggest coupled experimental-analytical-computational approaches utilizing synchrotron X-ray diffraction, to solve an inverse problem and find fields of all components of stress and plastic strain tensors and friction rules before, during, and after α-ω PT in strongly plastically predeformed Zr. Results are in good correspondence with each other and experiments. Due to advanced characterization, the minimum pressure for the strain-induced α-ω PT is changed from 1.36 to 2.7 GPa. It is independent of the plastic strain before PT and compression-shear path. The theoretically predicted plastic strain-controlled kinetic equation is verified and quantified. Obtained results open opportunities for developing quantitative high-pressure/stress science, including mechanochemistry, synthesis of new nanostructured materials, geophysics, astrogeology, and tribology.

Low-temperature high-pressure spectroscopy of lanthanum lutetium gallium garnet crystals doped withCr3+andNd3+

Low-temperature luminescence measurements under high pressures in diamond-anvil cell of nonstoichiometric lanthanum lutetium gallium garnet (LLGG) doped with Cr 3 + ions and nonintentionally with Nd 3 + ions are reported.Three nonequivalent Cr 3 + centers were found in the crystal using this technique. The results also reveal information about the electronic structure of different Cr 3 + centers in those crystals. Cr 3 + ions in a LLGG crystal experience a very low crystal field strength. The energy differences between the 4 T 2 and 2 E levels are negative, and equal to about - 1100 cm - for two of those centers and about -1500 cm - 1 for the third one. The spectral results were corroborated by a theoretical analysis of the luminescence decay times as a function of pressure, which allowed one to establish the exact values of the crystal-field parameter Dq at ambient pressure for those centers. The crystal exhibits a large inhomogeneous broadening of the R lines, associated with nonstoichiometry. In addition to the Cr 3 + luminescence also luminescence of Nd 3 + ions was detected in the LLGG crystals. One of the Nd 3 + luminescence lines, associated with the 4 F 3 / 2 4 I 9 / 2 transition. is strongly dependent on pressure, with a pressure coefficient equal to 0.96′0.02 cm - 1 /kbar, which makes this system interesting as a pressure gauge in the infrared region.