Electric and ferro-piezoelectric properties of (SBN)1-x(BTN)x, ceramics obtained from amorphous precursors

Ceramics of compositions within the solid solution system (SrBi2Nb2O9)(1-x)(Bi3TiNbO9)(x) have been obtained for 0 less than or equal to x less than or equal to 1. The preparation method for the ceramic precursor powder consists of mechanochemical activation by milling of the oxides and carbonates mixture until amorphization. Sintered ceramics obtained from amorphous powders are not textured and have high densifications (up to 98% of theoretical density). Ferro-piezoelectric characterisation of the ceramics has been carried out and the electric properties of ceramics with x = 0.50 and x = 0.25 compositions were exhaustively studied. Dielectric characterisation shows several anomalies in the dielectric constant and a lineal variation of the: Curie temperature as a function of the composition. The anomaly at temperatures close to 500 degreesC, more significant for x = 0.25 composition, is, surely, originated by the contribution of any dipolar contribution (pole-defects) to the dielectric constant. The Arrhenius plots of the D.C. conductivity show different behaviour in the: heating and cooling run of the first thermal cycle, being less pronounced in subsequent cycling. For x = 0.50 composition on heating, four slopes can be clearly drawn, but only one slope appears on cooling from high temperature. Explanations are given based on the point defect thermal evolution and their relation with extended defects (boundary grains and ferroelectric domains). (C) 2001 Elsevier Science Ltd. All rights reserved.