Reaction between the tetragonal tungsten bronze niobate K2Sr4Nb10O30 and the perovskite Pb(Mg1/3Nb1/3)O-3

The search for dielectric materials with a high dielectric constant and epsilon(r)'=f(T) curves with a flat profile fitting the X7R specification is still ongoing. Promising results were obtained by mixing compounds with closely related structures, such as the tetragonal tungsten bronze (TTB) niobate K2Sr4Nb10O30 and the perovskite Pb(Mg1/3Nb2/3)O-3 (PMN). The present study, based on three methods of synthesis, explores the origin of the spreading out of the dielectric curves epsilon(r)'=f(T). For the composition 10x Kr0.2Sr0.4NbO3(KSN)+(1 - x)Pb(Mg1/3Nb2/3)O-3(PMN) with x=0.3-0.6, the three synthesis methods provided similar characteristics and for the highest perovskite ratio (x=0.3), the epsilon(r)'=f(T) curve exhibits a flat profile. When lithium is used as a sintering agent, epsilon(r)'=f(T) curves present a linear dependency with the temperature. These materials are also characterized by a structural and a microstructural inhomogeneity. Two phases TTB and perovskite type, different from KSN and PMN, an present after calcination and sintering, but not evenly distributed. The PbO loss during sintering also contributes to the evolution of the properties of the material.