Synchrotron diffraction study of YCrO3 perovskite under high pressure

Due to its electric, magnetic, piezoelectric and optical properties, YCrO3 perovskite has become an attracting material (e.g. multifunctional biferroic, interconnection for the SOFC’s). A recent study [1] revealed that the YAlO3–YCrO3 system exhibits the lowest relaxation coefficient, if compared with other structures hosting Cr3+ in octahedral coordination. Despite the many studies devoted to assess the high pressure (HP) behavior of orthorhombic perovskites, data on YCrO3 under HP conditions are lacking. Thus, we investigated YCrO3 using synchrotron powder diffraction, up to 60 GPa. The fitted P-V data gave a V0 = 218.23(4) Å3, and a bulk modulus KT0 = 208.4(5) GPa, with a K'0 = 3.7(1). The elastic moduli showed that the b-axis is appreciably less compressible than both a- and c-axis (Ka0 = 195(5) GPa, Kb0 = 223(7) GPa, and Kc0 = 200(6) GPa, respectively). The polyhedral bulk moduli for YO12 and CrO6 polyhedra are almost equivalent with V0,poly, Kp0: 46.09(2) Å3, 254(2) GPa for YO12, and 10.40(1) Å3, 251(5) GPa for CrO6. Differently, it has been reported that for YAlO3 the b-axis is significantly more compressible than both c and a [2], meaning that the two structures under pressure show a different anisotropic behavior along [101] (both YCrO3 and YAlO3). Furthermore, for the YAlO3 the compressibility of the A site is ~15% less than that of the B site. Such contrasting trends can be explained by the stronger confinement of Y ions in YAlO3 due to the smaller size of octahedral network in the YAlO3 compared to the YCrO3. The decrease of <B–O> distance, from YCrO3 to YAlO3, was found to be accompanied by shortening of the <A–O> distance and decreasing of interpolyhedral tilting [1]. As a result, Y cation in YAlO3 are in stiffer site than in YCrO3. In the latter the A site is easier to compress and does not hamper the octahedral tilting expected at HP conditions. [1]G. Cruciani, M. Ardit, M. Dondi, F. Matteucci, M. Blosi, M. C. Dalconi, and S. Albonetti, J. Phys. Chem. A 2009, 113, 13772. [2]N. Ross, J. Zhao, and R. Angel, J. Solid State Chem. 2004, 177, 1276.