TY - JOUR
T1 - Protonated niobate/titanate pyrochlores via lead-acid exchange in Pb 1.5Nb2O6.5 and Pb2Nb 1.33Ti0.67O6.67
AU - Brune, Alicia B.
AU - Mangham, Robert I.
AU - Petuskey, William
N1 - Funding Information:
Acknowledgements The authors gratefully acknowledge Dr. Shuling Guo and Dr. J.-P. Belieres for obtaining DSC data, Dr. Z. Liu for taking SEM micrographs, Dr. K. Leinenweber and F. He for helping with XRD, and Barry Wilkens for performing the Ion Beam Analysis. Financial support from the Air Force Office of Scientific Research under grants 155A-99-0031 and FA95500410153 is also gratefully acknowledged.
PY - 2008/1
Y1 - 2008/1
N2 - Hydrogen-based niobates and niobate-titanates were derived from the pyrochlores Pb1.5Nb2O6.5 (PN) and Pb 2Nb1.33Ti0.67O6.67 (PNT) by ion exchange in acid baths, affording sub-micron size white powders. The niobium sublattice was left intact, as shown by X-ray diffraction. A combination of stripping and thermogravimetric analyses gave the effective formulas H 2.66Pb0.17Nb2O6.5•0.5H 2O (HPN) and H3.88Pb0.06Nb 1.33Ti0.67O6.67•0.33H2O (HPNT). The corresponding structural refinements gave good fits to the XRD data. Densities measured by He pycnometry agreed with densities calculated from XRD analyses and the effective formulas. Thermal stability was assessed by TGA, DSC, and XRD. With increasing temperature, HPN and HPNT lost weight (H 2O), becoming amorphous, and then transforming to crystalline phases, with greatly reduced particle size. HPN was more stable than HPNT. The electrical conductivities of powder compacts in wet atmospheres were moderate and attributed mainly to proton conduction; i.e., 10-6 to 10 -5 S cm-1 for HPN and 10-7 to 10-6 S cm-1 for HPNT (from room temperature to 230 °C). Experimental results were interpreted in terms of Nb(V) being a stronger electron acceptor than Ti(IV).
AB - Hydrogen-based niobates and niobate-titanates were derived from the pyrochlores Pb1.5Nb2O6.5 (PN) and Pb 2Nb1.33Ti0.67O6.67 (PNT) by ion exchange in acid baths, affording sub-micron size white powders. The niobium sublattice was left intact, as shown by X-ray diffraction. A combination of stripping and thermogravimetric analyses gave the effective formulas H 2.66Pb0.17Nb2O6.5•0.5H 2O (HPN) and H3.88Pb0.06Nb 1.33Ti0.67O6.67•0.33H2O (HPNT). The corresponding structural refinements gave good fits to the XRD data. Densities measured by He pycnometry agreed with densities calculated from XRD analyses and the effective formulas. Thermal stability was assessed by TGA, DSC, and XRD. With increasing temperature, HPN and HPNT lost weight (H 2O), becoming amorphous, and then transforming to crystalline phases, with greatly reduced particle size. HPN was more stable than HPNT. The electrical conductivities of powder compacts in wet atmospheres were moderate and attributed mainly to proton conduction; i.e., 10-6 to 10 -5 S cm-1 for HPN and 10-7 to 10-6 S cm-1 for HPNT (from room temperature to 230 °C). Experimental results were interpreted in terms of Nb(V) being a stronger electron acceptor than Ti(IV).
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U2 - 10.1007/s10853-007-2170-0
DO - 10.1007/s10853-007-2170-0
M3 - Article
AN - SCOPUS:37249009208
SN - 0022-2461
VL - 43
SP - 621
EP - 634
JO - Journal of Materials Science
JF - Journal of Materials Science
IS - 2
ER -