0000000000322839
AUTHOR
J.l. Rodrigo
High temperature neutron diffraction study of sodium di-tin tri-phosphate
Abstract High temperature high resolution neutron diffraction study of the crystal chemistry of NaSn 2 (PO 4 ) 3 has been completed, at four different temperatures, applying the Rietveld method to the experimental neutron diffraction profile of a synthetic crystalline powder. Below the phase transition (∼860 K) the space group has been determined to be R3 which changes to R3c in the high temperature phase. No chemical bond breaks through the transition. The change in temperature makes the SnO 6 polyhedra rotate around the three fold axis in both structures. The PO 4 polyhedra rotate strictly around the two fold axis in the high temperature phase, but around the [0001] direction in the low t…
Thermal expansion of LiZr2(PO4)3: Water inclusion influence
Abstract Lattice thermal expansion has been measured on three samples of composition LiZr 2 (PO 4 ) 3 , prepared by (i) a ceramic method, (ii) a gel-route and (iii) a nonstoichiometric ceramic. The first sample is monoclinic (?), with a transition at 50°C to rhombohedral. The second is clearly monoclinic with lattice parameters depending on the calcination temperature (700 to 1200°C. The third kind of synthesis yielded a new PO 4 -deficitary rhombohedral structure. X-ray diffraction measurements in a high temperature camera have been made from room temperature up to 1100°C. Lattice parameters, as well as their dependence on temperature are different for the three samples. While thermal expa…
Phase transition in NaSn2(PO4)3 and thermal expansion of NaMIV2 (PO43; MIV = Ti, Sn, Zr
Abstract NaSn2(PO4)3 presents a fast and reversible second order phase transition about 575°C. Both phases above and below the transition point are rhombohedral. The high temperature phase is isostructural with NaTi2(PO4)3 and NaZr2(PO4)3, NZP structure. The lattice thermal expansion of these three compounds has been determined from x-ray diffraction data at different temperatures ranging from room temperature up to 1000°C. Differences in behaviour are discussed in relation to the structure.