Microstructure and low-temperature relaxor behavior of dense K2Nb4O11 ceramics derived from sol-gel route

High purity tetragonal tungsten-bronze type K2Nb4O11 fine powders were synthesized via an economical sol-gel route and the crystal structure was solved by Rietveld refinement of X-ray powder diffraction. Structural evolution during calcination was found to occur via translation of the edge shared octahedra into a corner sharing coordination. Using nano-structured powder as precursor, dense K2Nb4O11 ceramics were successfully fabricated by pressure-less sintering. This maiden achievement allowed for primary dielectric characterization of this ceramic compound. The quantitative analysis based on empirical parameters, ΔTm and γ, reveals a relaxor nature in the temperature region below 200 K. More remarkably, the dielectric constant and loss are almost frequency independent in the wide range of 1 Hz-1 MHz at room temperature and a high dielectric constant and low loss (ɛr = 200 and tan δ = 0.007) makes them good materials for dielectric components for embedded capacitors and multilayer ceramic capacitors.