ISSN:
1573-4803
Quelle:
Springer Online Journal Archives 1860-2000
Thema:
Maschinenbau
Notizen:
Abstract The reaction chemistry involved in the synthesis of perovskite Pb(Mg1/3Nb2/3)O3 [Pb3MgNb2O9] was studied by the solid state reaction technique using precursor oxides as reactants. At the initial stage of the reaction process, a large fraction of PbO present in the mixtures combined with Nb2O5 and a small amount of MgO to form an oxygen-deficient pyrochlore phase with a composition Pb1.714(Mg0.286Nb1.714)O6.286 [Pb6MgNb6O22]. The pyrochlore phase thus formed further reacted with the remaining PbO and MgO to yield the perovskite Pb(Mg1/3Nb2/3)O3. The pyrochlore Pb1.714(Mg0.286Nb1.714)O6.286 accomodates a small amount of PbO into its lattice and forms a narrow homogeneity range which extends from the composition Pb1.714(Mg0.286Nb1.714)O6.286 [Pb6MgNb6O22] to a composition Pb2(Mg0.286Nb1.714)O6.571 [Pb7MgNb6O23] with a corresponding increase in the lattice constant value from a = 10.586 to 10.601 Å. The pyrochlore phase melts incongruently at a temperature near 1230°C to yield Mg4Nb2O9 and a liquid. Below this temperature, the perovskite Pb(Mg1/3Nb2/3)O3 coexists with the pyrochlore solid solutions. However, the compound Pb(Mg1/3Nb2/3)O3 is not compatible with Nb2O5 and these two phases react with one another to form the pyrochlore Pb1.714(Mg0.286Nb1.714)O6.286 and MgO.
Materialart:
Digitale Medien
URL:
http://dx.doi.org/10.1023/A:1004767823668
