M. Valant et D. Suvorov, New high-permittivity AgNb1-xTaxO3 microwave ceramics: Part I, Crystal structures and phase-decomposition relations, J AM CERAM, 82(1), 1999, pp. 81-87
The crystal structure of monophasic AgNb1/2Ta1/2O3 was investigated via Rie
tveld refinement using powder X-ray diffractometry (XRD) data. The study re
vealed a monoclinic unit cell of the P2/m space group with the following un
it-cell parameters: a = 3.9286(3) Angstrom, b = 3.9259(2) Angstrom, c = 3.9
302(3) Angstrom, and beta = 90.49(1)degrees. High-temperature XRD studies o
f the decomposition of AgNb1/2Ta1/2O3 showed that the kinetics of the decom
position are influenced by the volatilization of silver, Suppression of sil
ver volatilization by enclosing the sample in a corundum tube and applying
an oxygen atmosphere yielded sintered, almost-monophasic AgNb1/2Ta1/2O3 cer
amics with >97 % of the theoretical density, The Ag-8(Nb,Ta)(26)O-69 phase,
which regularly appeared as a result of partial decomposition of Ag(Nb1-xT
ax)O-3, was studied by energy-dispersive spectroscopy analysis and XRD. The
Ag-8(Nb,Ta)(26)O-69 phase exhibited a bronzelike orthorhombic structure wi
th the follovcing unit-cell parameters: a = 37.116(5) Angstrom, b = 12.432(
3) Angstrom, and c = 7.826(2) Angstrom. Indexed powder diffraction data for
Ag-8(Nb,Ta)(26)O-69 have been reported.