Novel, Oxygen-Deficient n ) 3 RP-Member Sr 3 NdFe 3 O 9-δ and Its Topotactic Derivatives D. Pelloquin,* J. Hadermann, M. Giot, V. Caignaert, C. Michel, M. Hervieu, and B. Raveau Laboratoire CRISMAT-ENSICAEN, UMR6508, 6, Bd du Mare ´ chal Juin, 14050 Caen Cedex, France Received October 15, 2003. Revised Manuscript Received February 5, 2004 The stabilization of the n ) 3 member of the Ruddlesden-Popper series has been investigated in the Sr-Nd-Fe-O system. A new series of phases closely derived from RP- type structures has been synthesized and characterized by X-ray diffraction and electron microscopy. The control of the oxygen stoichiometry first allowed us to isolate a new highly oxygen deficient, layered oxide, Sr 3 NdFe 3 O 9-δ . The structural analysis has revealed that this oxide crystallizes in an orthorhombic lattice (a p 2 × a p 2 × 28 Å), distorted with regard to the ideal I-type symmetry of the RP-type structures. Interestingly, this oxygen- deficient n ) 3 RP-member reacts at room temperature with ambient moisture to transform into a hydrated oxyhydroxide, Sr 3 NdFe 3 O 7.5 (OH) 2 ·H 2 O. This second phase can be dehydrated topotactically in two steps by heating to 400 °C, leading to Sr 3 NdFe 3 O 7.5 (OH) 2 and then Sr 3 - NdFe 3 O 8.5+δ , respectively. The reversible character of these hydration/hydrolysis reactions is also demonstrated. Introduction Titanates of the Ruddlesden and Popper series Sr n+1 - Ti n O 3n+1 1 represent the first members of a huge family of layered oxides that are closely related to perovskite. Starting from these compounds, whose structure is built up from the intergrowth of a single rock salt layer [SrO] with multiple perovskite layers [SrTiO 3 ] n , new struc- tural series were generated by increasing the multiplic- ity of the rock salt layers, especially introducing Bi, Tl, Pb, and Hg, or by creating ordered oxygen deficiency within the multiple perovskite layers. This is exempli- fied by the numerous high T c superconducting cuprates that were discovered these last 15 years. 2-3 Interest for the RP structure was also renewed with the discovery of colossal magnetoresistance in the layered man- ganites. 4-5 Several bismuth-, thallium-, and lead-based cobaltites 6-9 and ferrites 10-16 and a chromium-based oxide, Sr 4 Cr 2.5 O 9 , 17 derived from RP-type structures were also isolated. The existence of the three first members of the RP series Sr n+1 Fe n O 3n+1 , 18-20 all characterized by the pres- ence of Fe 4+ , makes the system Sr-Fe-O very attrac- tive for the generation of new RP phases. In such a system, the introduction of a lanthanide on the Sr sites or of carbonate groups in the octahedral layers leads to the formation of Fe 3+ derivatives, as shown by the existence of RP-type oxides in the system LaSr 3 Fe 3 - O 10-x , 21 with x varying from 0 to 1, and oxycarbonates Sr 4 Fe 3-x O 10-4x (CO 3 ) x . 22 We have investigated the Sr- Nd-Fe-O system, controlling the oxygen stoichiometry * Corresponding author. E-mail: denis.pelloquin@ismra.fr. Permanent address: EMAT Laboratory, University of Antwerpen- RUCA, Groenenborgerlaan 171, 2020 Antwerpen, Belgium. (1) Ruddlesden, S. N.; Popper, P. Acta Crystallogr. 1957, 10, 538; ibid 1958, 11, 54. (2) See for a review, Rao, C. N.; Raveau, B. Transition Metal Oxides; Wiley-VCH: New York, 1998. (3) See for a review, Raveau, B.; Michel, C.; Hervieu, M.; Groult, D. Crystal Chemistry of High Tc Superconducting Copper Oxides; Springer Series Materials Science; Springer-Verlag: Berlin, 1991. (4) Kimura, K.; Hatsuda, K.; Ueno, Y.; Kajimoto, R.; Mochizuki, A.; Yoshizawa, H.; Nagai, T.; Matsui, Y.; Yamazaki, A.; Tokura, Y. Phys. Rev. B 2001, 65, 20407. (5) Maignan, A.; Martin, C.; Van Tendeloo, G.; Hervieu, M.; Raveau, B. J. Mater. Chem. 1998, 8, 2411. (6) Tarascon, J. M.; Miceli, P. F.; Barboux, P.; Hwang, D. M.; Hull, G. W.; Giroud, M.; Greene, L. H.; Lepage, Y.; McKinnon, W. R.; Tselepis, E.; Pleizier, G.; Eibschutz, M.; Neumann, D. A.; Phyne J. J. Phys. Rev. B 1989, 39, 11587. (7) Coutanceau, M.; Dordor, P.; Doumerc, J. P.; Grenier, J. C.; Maestro, P.; Pouchard, M.; Semidubsky, D.; Seguelong, T. Solid State Commun. 1995, 96, 569. (8) Groult, D.; Martin, C.; Maignan, A.; Pelloquin, D.; Raveau, B. Solid State Commun. 1998, 105, 583. (9) Pelloquin, D.; Masset, C.; Maignan, A.; Hervieu, M.; Michel, C.; Raveau, B. J. Solid State Chem. 1999, 148, 108. (10) Pelloquin, D.; Allix, M.; Michel, C.; Hervieu, M.; Raveau, B. Philos. Mag. B 2001, 81 (11), 1669-1685. (11) Pelloquin, D.; Wahl, A.; Masset, A. C.; Maignan, A.; Michel, C.; et Raveau, B. J. Solid. State. Chem. 2000, 154 (2), 375-383. (12) . Retoux, R.; Michel, C.; Hervieu, M.; Nguyen, N.; Raveau, B. Solid State Commun. 1989, 69, 599. (13) Daniel, Ph.; Barbey, L.; Nguyen, N.; Ducouret, A.; Groult, O.; Raveau, B. J. Phys. Chem. Solids 1994, 55, 795. (14) Caignaert, V.; Daniel, Ph.; Nguyen, N.; Groult, O.; Raveau, B. J. Solid State Chem. 1994, 112, 126. (15) Hervieu, M.; Pelloquin, D.; Michel, C.; Calde `s, M. T.; Raveau, B. J. Solid State Chem. 1995, 118, 227. (16) Boullay, Ph.; Domenges, B.; Groult, D.; Raveau, B. J. Solid State Chem. 1996, 124, 1. (17) Nguyen, N.; Groult, D.; Caignaert, V.; Ducouret, A.; Raveau, B. Phys. B, Condens. Matter 1996, 228, 251. (18) Dann, S. E.; Weller, M. T.; Curie, D. B. J. Solid State Chem. 1991, 92, 237. (19) Dann, S. E.; Weller, M. T.; Curie, D. B. J. Solid State Chem. 1992, 97, 179. (20) Brisi, C.; Rolando, Ann. Chim. (Rome) 1969, 59, 385. (21) Lee, J. Y.; Swinn, J. S.; Ea, P.; Steinfink, H.; Reiff, W. M.; Pei, S.; Jorgensen, J. D. J. Solid State Chem. 1993, 103, 1. (22) Bre ´ard, Y.; Michel, C.; Hervieu, M.; Raveau, B. J. Mater. Chem. 2000, 10, 1043. BATCH: cm5b07 USER: ckt69 DIV: @xyv04/data1/CLS_pj/GRP_cm/JOB_i10/DIV_cm030351n DATE: March 26, 2004 10.1021/cm030351n CCC: $27.50 © xxxx American Chemical Society PAGE EST: 9.4 Published on Web 00/00/0000 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50