We report a structural evolution analysis of the long-range and local order and disorder of lead scandium niobate (PSN) down to 10 K, using a combination of neutron and x-ray diffraction on powder and single crystals. The structure of PSN is discussed and compared with those of simple perovskite compounds and . In PSN the existence of a long-range but still disordered ferroelectric phase, different from those of simple perovskites, is evidenced. The disorder of lead and scandium/niobium atoms on short-, medium- and long-range scales is discussed in connection with the dielectric properties of these materials.

Non‐photochemical laser‐induced nucleation (NPLIN) has been a growing field of study since 1996, and more than 40 compounds including organics, inorganics and proteins have now been probed under various conditions (solvents, laser types, laser beams etc.). The potential advantages of using this technique are significant, in particular polymorphic control. To realize these benefits, the objective is a carefully designed experimental setup and highly controlled parameters, for example temperature and energy density, in order to reduce the uncertainty regarding the origin of nucleation. In this paper, a new experimental setup designed to study NPLIN is reported. After a full technical description of the present setup, the different functionalities of this device will be illustrated through results on glycine. Glycine crystals obtained through NPLIN nucleate at the meniscus and exhibit different morphologies. The nucleation efficiency, as a function of the supersaturation of the solution used and the laser beam energy density, has also been established for a large number of samples, with all other parameters held constant.

International audienceThis paper reports for the first time the crystallization of the carbamazepine (CBZ) molecule in two solvents (methanol and acetonitrile) using the non-photochemical laser-induced nucleation (NPLIN) technique. The metastable zone of CBZ is first determined experimentally for different temperatures in both solvents. Then, the prepared solutions are irradiated by a 532 nm wavelength nanosecond pulsed laser and permitted to obtain CBZ crystals of phases I and III. The impact of laser power and polarization (circularly (CP) and linearly (LP)) on the CBZ crystallization efficiency in both solvents is determined through experiments. According to the results, the crystallization efficiency is significantly higher in methanol than in acetonitrile, and it is higher in solutions irradiated by CP laser than those by LP laser. Moreover, the irradiation of an acetonitrile solution by a LP laser results in CBZ phases I and III, whereas irradiation by the CP laser leads to CBZ phase III crystals. An ab initio determination of the interaction energy of different pairs of CBZ has been carried-out that enables the explanation of the nucleation in acetonitrile for both polarizations. In methanol, only CBZ phase III is obtained, which is in agreement with the ability of methanol to create noncovalent interactions preventing the CBZ phase I and II nucleation