Effects of experimental parameters on characterization of AgNb1−xTaxO3 materials by a modified sol–gel route

Abstract

Nano-sized AgNb1−xTaxO3 (x = 0.4) ceramic powders were synthesized by a modified citrate sol–gel route. Homogeneous Ag–Nb–Ta precursor gel was prepared with silver citrate, niobium citrate, and tantalum citrate as source of Ag, Nb and Ta, respectively. Citrate acid and ethylene glycol were used as the complexing agents. The structural variation of the AgNb1−xTaxO3 powder with annealing temperature was studied by TG–DTA and X-ray diffraction. The precursor gel calcinated at 680 °C produced a pure perovskite phase. The effects of experimental parameters including pH value of the solution and the proportion of citric acid to the metal ions on the formation of homogeneous and microstructure of the powders were also investigated. The results indicated that a homogeneous Ag–Nb–Ta precursor gel with no precipitate was formed at about pH = 6 and the optimum molar ratio of citric acid and the metal ions were 2:1–3:1. The XRD data was analysis and the correlation between dielectric properties and (Nb,Ta)O6 octahedra was discussed.