No abstract

The infrared reflectance spectra of two LaMnO 3 crystals ͑pure and doped͒ have been measured at various temperatures between 300 and 10 K. The infrared active phonons of the two samples have been studied in detail and have been compared to recent lattice dynamics calculations. In the case of the undoped LaMnO 3 , the number of infrared active phonons agrees with the predictions of group theory. In contrast the phonon structures of the doped sample are broader and do not allow to identify all the expected lines.

In the crystal structure of hydrothermally synthesized disodium manganese fluoride orthophosphate, Na2{MnF[PO4]}, two kinds of cis-MnO4F2 octahedra share common vertices to form (Mn2F2Os) chains parallel to the b axis of the monoclinic unit cell. In the a and c directions these chains are linked by PO4 tetrahedra to form a three-dimensional framework of octahedra and tetrahedra. Na + cations are located in the channels of this framework structure. The problem of {OTXs} mixed anionic radical polymorphism is discussed. CommentThis work is part of our efforts to synthesize and investigate pegmatite-related phosphates. We are interested in the relationship between the structures of transition metal phosphates and the conditions of their formation (Yakubovich & Urusov, 1996). In addition to this, first row transition metal phosphates have become a focus for interest in recent years because of their possible use as new non-linear optical materials such as KTiOPO4 (KTP). The crystals of the new compound, Na2{MnF[PO4]}, were obtained as the product of hydrothermal growth experiments in the system NaF-MnO-(NH4)2HPO4-H20.

No abstract