Synthesis and dielectric properties of magnesium niobate-magnesium tantalate solid solutions

Monophasic Oxides of the type MgNb2-xTaxO6 (0 less than or equal to x less than or equal to 2) have been synthesized by solid-state reactions using Mg (NO3)(2). 6H2O as the source of Mg. The oxides crystallize in the orthorhom bic columbite structure till x = 1.75 and the tetragonal trirutile structur e for pure MgTa2O6 (X = 2.0). Sintered pellets at 1200 degreesC show dielec tric constant varying between 16 to 28 for the entire range of composition at a frequency of 500 kHz. The dielectric loss is nearly constant with freq uency, and varies between 0.004 and 0.01 for different compositions. The te mperature coefficient of dielectric constant (tau (E)) is 3 to -3 ppm/C (30 to 300 degreesC). Scanning electron micrographs reveal a gradual decrease in grain size with increase in Ta concentration with size of 7 to 10 micron s for the pure Nb phase sintered at 1200 degreesC while the pure Ta phase s hows a grain size of approximately 0.5 to 1 microns. (C) 2001 Elsevier Scie nce Ltd. All rights reserved.