The high pressure structural chemistry of zeolites has been thoroughly investigated and several unusual structural characteristics have been discovered, such as pressure induced expansion and superhydration [1-2]. However, to date few materials with layered structures have been studied [3]. Here, we present an in-situ high-pressure powder diffraction study of the layered metal phosphates α-zirconium phosphate and α-titanium phosphate [4-5]. Experiments were carried out in diamond anvil cells using a synchrotron X-ray source up to pressures of 10 GPa under hydrostatic and non-hydrostatic conditions. The GSAS suite of programs were used to carry out Rietveld analysis at each pressure step [6]. It was found that under hydrostatic conditions there is a linear decrease in all lattice parameters with pressure, a plot of unit cell volume versus pressure is shown below and it can be clearly seen that there is little hysteresis upon pressure release. Under non-hydrostatic conditions α-zirconium phosphate is almost amorphous by 10 GPa whilst α-titanium phosphate remains crystalline. Excessive line broadening in both samples meant full Rietveld analysis could not be carried out although lattice parameters could be obtained. Full details from the refinements, changes in distances, angles and bulk moduli will be presented.

References:

[1] Y. Lee, T. Vogt, J. A. Hriljac, J. B Parise and G. Artoli, J. Am. Chem. Soc., 124, 5466 (2002).

[2] J. A. Hriljac, Cryst. Rev., 12, 181 (2006).

[3] S. Nakano, T. Sasaki, K. Takemura and M. Watanabe, Chem. Mater., 10, 2044 (1998).

[4] A. Clearfield and U. Costantino, Supramolecular Chemistry, 7, 107 (1996).

[5] S. Bruque, M. A. G. Aranda, E. R. Losila, P. Olivera-Pastor and P. Maireles-Torres, Inorg. Chem., 34, 893 (1995).

[6] A. C. Larson and R. B. Von Dreele, “General Structure Analysis System (GSAS)”, Los Alamos National Laboratory Report LAUR 86-748 (2000).

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1. High-pressure phase transitions in AI₃ (A = Rb, Cs, Tl, NH₄) Triiodides
2. Pair distribution studies of ion-exchanged α-zirconium phosphate
3. Powder diffraction studies of mixed titanium zirconium phosphates