Effects of Pb(Mg 1/3 Ta 2/3 )O 3 and Pb(Zn 1/3 Nb 2/3 )O 3 substitution in the Pb(Mg 1/3 Nb 2/3 )O 3 -PbTiO 3 ceramic system on structure formation, crystallographic aspects, and dielectric properties are discussed. Developed phases in the B-site precursor and perovskite systems were studied by X-ray diffraction. Crystal symmetries and dimensions of the perovskite unit cell of the two systems are compared. Changing rates of the lattice parameter with substituent PbTiO 3 concentration in the two modified systems are virtually identical to that of the unmodified Pb(Mg 1/3 Nb 2/3 )O 3 -PbTiO 3 system. Weak-field lowfrequency dielectric responses of the ceramics were investigated. The dielectric maximum temperatures of the two perovskite systems shifted almost linearly with compositional change. Dielectric constant spectra at low concentrations of PbTiO 3 exhibited typical diffuse phase transition behavior, whereas those at high PbTiO 3 concentrations were rather sharp. The phase transition modes reflected on the dielectric spectra were quantitatively analyzed in terms of diffuseness parameters.
Octahedral cations of Mg and Ta in Pb[(Mg1/3Ta2/3)0.8Ti0.2]O3 were replaced independently as well as simultaneously by Zn and Nb, respectively, to investigate the effects of composition modification on phase formation and dielectric properties. When Mg was replaced by Zn, the perovskite formation yields decreased continuously to 0% with the Zn fraction. In contrast, nearly phase‐pure perovskite powders could be prepared when Ta and the Mg‐Ta complex were replaced by Nb and Zn‐Nb, respectively. Dielectric relaxation with diffuse phase transition was observed at most of the compositions. Dielectric maximum temperatures increased steadily with the substituent fractions, whereas variations of the maximum dielectric constant were dependent heavily on the substituent species.
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