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 an d epsilon(r)'=f(T) curves with a flat profile fitting the X7R specific ation is still ongoing. Promising results were obtained by mixing comp ounds 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, explo res 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(Mg1/3Nb 2/3)O-3(PMN) with x=0.3-0.6, the three synthesis methods provided simi lar characteristics and for the highest perovskite ratio (x=0.3), the epsilon(r)'=f(T) curve exhibits a flat profile. When lithium is used a s a sintering agent, epsilon(r)'=f(T) curves present a linear dependen cy with the temperature. These materials are also characterized by a s tructural and a microstructural inhomogeneity. Two phases TTB and pero vskite type, different from KSN and PMN, an present after calcination and sintering, but not evenly distributed. The PbO loss during sinteri ng also contributes to the evolution of the properties of the material .