Temperature-compensated BaV2O6-Ba2V2O7 ceramic composite for ULTCC applications

A temperature-compensated dielectric ceramic composite in the BaV2O6-Ba2V2O7 system has been achieved using rule of mixtures and subsequent modulation of composition based on experiments. The BaV2O6 and Ba2V2O7 powders, synthesized by the solid-state route, are mixed in various compositions and sintered between 525 and 600 °C to produce the composites. The effect of sintering temperature and duration on the density, stability of the phases, microstructure and microwave dielectric properties have been investigated. The BaV2O6 and Ba2V2O7 phases coexist up to 575 °C without any reaction, as established by XRD and SEM-EDS analyses. The composite with 0.60 weight (wt) fraction of BaV2O6 sintered to 96% TD at 550 °C and exhibits a temperature coefficient of resonance frequency (τf) very close to zero (+0.2 ppm/K). The relative permittivity (εr = 10.73), loss tangent (tanδ = 3.66 × 10-4), and quality factor (Qu × f = 30,000 GHz) obtained for this composite are adequate for microwave dielectric applications. This composite shows a linear coefficient of thermal expansion of 14 ppm/K. The excellent chemical compatibility with Al during cofiring, makes this composite a suitable choice for ULTCC application.