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

Abstract

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.