A New Microporous Zeolitic Silicoborate (ITQ-52) with Interconnected Small and Medium Pores

A new zeolite (named as ITQ-52) having large cavities and small and medium channels has been synthesized. This was achieved by using a new family of amino-phosphonium cations as organic structure directing agents (OSDA). These cations contain P–C and P–N bonds, and therefore they lie between previously reported P-containing OSDA, such as tetraalkylphosphonium and phosphazenes. In this study, it has been found that 1,4-butanediylbis­[tris­(dimethylamino)]­phosphonium dication is a very efficient OSDA for crystallization of several zeolites, and in some particular conditions, the new zeolite ITQ-52 was synthesized as a pure phase. The structure of ITQ-52 has been solved using high-resolution synchrotron X-ray powder diffraction data of the calcined solid. This new zeolite crystallizes in the space group <i>I</i>2<i>/m</i>, with cell parameters <i>a</i> = 17.511 Å, <i>b</i> = 17.907 Å, <i>c</i> = 12.367 Å, and β = 90.22°. The topology of ITQ-52 can be described as a replication of a composite building unit with ring notation [4³5⁴6¹] that gives rise to the formation of an interconnected 8R and 10R channel system

Phase Transformations in the CeO₂–Sm₂O₃ System: A Multiscale Powder Diffraction Investigation

The structure evolution in the CeO₂–Sm₂O₃ system is revisited by combining high resolution synchrotron powder diffraction with pair distribution function (PDF) to inquire about local, mesoscopic, and average structure. The CeO₂ fluorite structure undergoes two phase transformations by Sm doping, first to a cubic (C-type) and then to a monoclinic (B-type) phase. Whereas the C to B-phase separation occurs completely and on a long-range scale, no miscibility gap is detected between fluorite and C-type phases. The transformation rather occurs by growth of C-type nanodomains embedded in the fluorite matrix, without any long-range phase separation. A side effect of this mechanism is the ordering of the oxygen vacancies, which is detrimental for the application of doped ceria as an electrolyte in fuel cells. The results are discussed in the framework of other Y and Gd dopants, and the relationship between nanostructuring and the above equilibria is also investigated

A New Microporous Zeolitic Silicoborate (ITQ-52) with Interconnected Small and Medium Pores

A new zeolite (named as ITQ-52) having large cavities and small and medium channels has been synthesized. This was achieved by using a new family of amino-phosphonium cations as organic structure directing agents (OSDA). These cations contain P–C and P–N bonds, and therefore they lie between previously reported P-containing OSDA, such as tetraalkylphosphonium and phosphazenes. In this study, it has been found that 1,4-butanediylbis­[tris­(dimethylamino)]­phosphonium dication is a very efficient OSDA for crystallization of several zeolites, and in some particular conditions, the new zeolite ITQ-52 was synthesized as a pure phase. The structure of ITQ-52 has been solved using high-resolution synchrotron X-ray powder diffraction data of the calcined solid. This new zeolite crystallizes in the space group <i>I</i>2<i>/m</i>, with cell parameters <i>a</i> = 17.511 Å, <i>b</i> = 17.907 Å, <i>c</i> = 12.367 Å, and β = 90.22°. The topology of ITQ-52 can be described as a replication of a composite building unit with ring notation [4³5⁴6¹] that gives rise to the formation of an interconnected 8R and 10R channel system