Philippe Guy Paul Sciau

TL;DR: In this paper, the symmetry of the phases in disordered perovskite has been investigated using X-ray and synchrotron radiation, showing that the compound is a monoclinic ferroelectric at 293 K, undergoes a structural transition to another tetragonal state at about 355 K and finally transforms into a cubic form at approximately 376 K.

TL;DR: In this article, the ferroelastic symmetry changes of lead-based complex perovskite PbFeY0.5Ta0.3 are investigated by means of single crystal x-ray diffraction and observations in polarized light microscopy at different temperatures.

TL;DR: In this paper, the structures of MgV2O5 and δLiV2 O5 have been determined from X-ray powder diffraction Rietveld analysis at 294 and 83 K. The main difference between the two is induced by the higher polarization of the magnesium atoms compared to the lithium atoms, which leads to higher puckering angles of 21.0° and 11.3°, respectively.

TL;DR: The paraelectric and the ferroelectric/ferroelastic structures of Pb(2)KNb(5)O(15) have been refined by the Rietveld method from neutron and X-ray powder diffraction data and it was established that the Pb atoms situated on the 15-coordinate sites are not on the special position (2mm) but are distributed over two disordered positions as in the tetragonal phase of P b(2).

TL;DR: In this article, a quadratic magnetoelectric effet was detected in the incommensurate antiferro-magnetic phase of BaMnF4 and the eight third order coefficients have been determined at 4K: βxxx = 1.1 10−19 s.A−1, βxzz = -1.6 10− 19 s.