The growing interest in the inclusion compounds of the alkali metals in zeolites stems from their potential use as basic catalysts1 and increasingly from a rich variety of observations relating to their electronic, magnetic and optical A considerable volume of electron spin resonance (ESR) investigations has demonstrated the existence of a range of brightly colored paramagnetic centers-&'"-"+ and N+"'-')+ (m = 3,4; n = 3-6)-in zeolites X, Y, and A?-'5 Structures of zeolites containing cesium, rubidium, potassium, and sodium clusters have been reported by Seff and co-workers16-19 and by Armstrong et al.?n-22 but the location of the single-electron ionic cluster Na3+ continues to be the subject of debate.'n.11.23.24The incorporation of larger amounts of alkali metal results in dark solids with single-line ESR spectra, widely attributed to the formation of metallic clusters within the zeolite pores?s More recent work has cast doubt on this interpretation?5 and it has been proposed that in sodium-loaded sodium zeolite Y (Nd Na-Y), for example, the ESR line results from the interaction ' Rutherford Appleton Laboratory. Current Address: School of Chem+University of Birmingham.

The structure and electronic properties of the compound resulting from the reaction of cesium vapor with dehydrated cesinm-exchanged zeolite A are reported here. Rietveld refinement of powder neutron diffraction data demonstrates the incorporation of at least two "excess" cesium atoms per primitive unit cell into the zeolite. The presence of the previously identified Cs4 linear unit was confirmed; in the present study, the different synthetic route leads to a higher concentration of the tetramer than previously reported, approaching one per primitive unit cell. Detailed structural analysis, using powder neutron diffraction, magnetic susceptibility, and electron spin resonance (ESR) studies, points to the formulation CS~'+ rather than the previously reported Cs43+. Accordingly, the compound is only weakly paramagnetic with less than 6% of the excess electrons forming localized paramagnetic centers. There are indications from the ESR g shift that this paramagnetism may originate from hole-based localized states, perhaps arisingout of some partial charge fluctuation in an (otherwise) filled Csd2+ electronic baud. Even for these paramagnetic centers, substantial electron-electron interactions lead toantiferromagneticordering below 10 K. Approximately threesodinmions per primitiveunitcell resulting from incomplete ion exchange were identified; these also appear to carry some excess electron density, and there is evidence for segregation of sodium and cesium cations within the zwlite.

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He completed his Ph.D. thesis in 1990 (with PPE) at Cambridge. At the time ofpublication ofthis article he becomes Royal Society Research Fellow at the University of Birmingham. Lee Woodall was born in Rochdale, England. He graduated ,from Oxford University (St. Catherines College) in 1991 and moved to Birmingham in 1992 to begin his Ph.D. in Inorganic Chemistry.

We analysed x-ray powder diffraction data of spray pyrolytic precursor powders for the oxide-powder-in-tube (OPIT) technology by means of the Rietveld method. For calcinations in air we find a typical phase composition of 2212, 14-24, 11, CP and 3321 at 800 °C (13 h). At 820 °C 2212 is in equilibrium with 14-24 and CP after 48 h calcination. In 8% O2 at 800 °C 2212 exists together with 14-24, 21, CP and CuO, in 99.999% N2 at 760 °C the stable phase assemblage consists of 2212, 21 and CuO. The highest amount of 2212 can be found in the powder calcined at 8% O2 (72.4 wt%) compared with 68.9 wt% for the powder calcined in 21% O2 and 69.3 wt% for the powder calcined in flowing N2. A first trace of 2223 can be observed in powders calcined in air at temperatures of 838 °C and 842 °C. The crystallographic features of the 2212 phase correlate with the calcination atmosphere: under reducing atmospheres the satellite reflections of the x-ray powder diffractogram disappear and the orthorhombic lattice distortion z increases due to Pb2+-incorporation into 2212. With increasing O-content the c lattice parameter becomes significantly shorter in samples calcined in oxidizing atmospheres. It is possible to infer a cationic ratio of Sr:(Sr + Ca) ≈ 0.12 for the 11 phase and Ca:(Ca + Sr + Bi) ≈ 0.57 for 14-24 in precursors from lattice parameter data.