Elastic properties of perovskite YCrO3 up to 60 GPa

Perovskite compounds are largely applied in several technological fields due to their peculiar electric, magnetic, piezoelectric and optical properties. YCrO3, a GdFeO3-type perovskite, has become an attracting material due to its multifunctional biferroic behavior [1], and to its recent use as interconnection for the SOFC’s [2]. A recent work revealed that the YAlO3–YCrO3 system exhibits the lowest relaxation coefficient, if compared with other structures hosting Cr3+ in octahedral coordination [3]. In the last decade, many studies have been devoted to assess the high pressure behavior of orthorhombic perovskites. However, data on YCrO3 under high-pressure conditions are lacking. For these reasons, we investigated the high pressure evolution of the YCrO3 perovskite (s.g. Pbnm) using synchrotron powder diffraction, up to 60 GPa. The P-V data, fitted with a third-order Birch–Murnagham equation of state gave a V0 = 218.23(4) Å3, and to a volumetric bulk modulus KT0 = 208.4(5) GPa, with a K'0 = 3.7(1), with a volume reduction of ~17.5% in the studied pressure range. The elastic moduli of the individual crystallographic axes 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), implying that YCrO3 became more distorted with increasing pressure. The polyhedral bulk moduli for YO12 and CrO6 polyhedra led to: V0,poly, Kp0: 46.09(2) Å3, 254(2) GPa for YO12, and 10.40(1) Å3, 251(5) GPa for CrO6. The volume compressibilities of the YO12 and CrO6 sites are therefore equivalent. That results are different to those previously reported for the orthorhombic YAlO3 perovskite in which the b-axis is significantly more compressible than both c and a [4]. Considering the elastic moduli of both YCrO3 and YAlO3, the two structures under pressure show a different anisotropic behavior along [101] (both YCrO3 and YAlO3 structures). Furthermore, for the YAlO3 perovskite the compressibility of the A site is ~15% less than that of the AlO6 octahedron [4]. 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 orthoaluminate compared to the orthochromate. As known from previous work [3], the decrease of mean octahedral bond distance, <B–O>, from YCrO3 to YAlO3 is accompanied by shortening of the average <A–O> distance and decreasing of interpolyhedral tilting. The associated strong confinement of Y cation in YAlO3 does not occur in YCrO3. Here the A site is easier to compress and does not hamper the enhance of octahedral tilting and rotation expected at high pressure conditions. [1] Serrao, C.; Kundu, A.; Krupanidhi, S.; Waghmare, U.; Rao, C. Phys. Rev. 2005, B72, 220101. [2] Wang, S.; Lin, B.; Dong, Y.; Fang, D.; Ding, H.; Liu, X.; Meng, G. J. Power Sources 2009, 188, 483. [3] Cruciani, G.; Ardit, M.; Dondi, M.; Matteucci, F.; Blosi, M.; Dalconi, M.; Albonetti, S. J. Phys. Chem. A 2009, 113, 13772. [4] Ross, N.; Zhao, J.; Angel, R. J. Solid State Chem. 2004, 177, 1276.