Dielectric Properties Of barium titanate Based Composites

In the last few decades there has been a growing interest in lead free piezoelectric materials. The main driving force is limitations due to environmental concern. The most well-known example is 2003 European Union’s RoHS... [ view full abstract ]

In the last few decades there has been a growing interest in lead free piezoelectric materials. The main driving force is limitations due to environmental concern. The most well-known example is 2003 European Union’s RoHS (Restriction of Hazardous Substances) directive, which has limited the use of lead in certain fields. Pb(Zr_xTi_1-x)O₃ (PZT) is the most commercially viable piezoelectric material due to its high piezoelectric constant, ability to operate in a wide temperature range. Unfortunately, it is lead-containing, thus falls under the restriction of RoHS.  In literature, most studies are focused on preparing high quality solid solution or composites at high temperatures which is not always desirable. However, a different approach can be used, where we focus on preparation at lower temperatures which can be advantageous in some cases. 

In our presentation broadband dielectric properties of BaTiO₃ (BT) based composites with core-shell structure in temperature range of 100 to 500 kelvins will be presented. The composites were prepared in two steps. BT, BiFeO3 (BF), BaTiO₃-Bi(Mg_0.5,Ti_0.5)O₃ (BT-BMT) and BaTiO₃-Bi(Mg_0.5,Ti_0.5)O₃-BiFeO₃ (BT-BMT-BF) nanoparticles were compressed with TiO₂ (ratio 1 : 1) in to low density pellets. Further, disk-shape pellets were submerged into barium hydroxide (Ba(OH)₂) for solvothermal solidification. In the end we obtain BT around BT, BF, BT-BMT and BT-BMT-BF particles. In such systems cores are stressed by barium titanate shell creating similar conditions as in morphotropic phase boundary (MPB), thus increasing dielectric and piezoelectric constants. We have investigated dielectric properties in broad frequency range of 4 different composite systems where core is a good dielectric, a relaxor, a ferroelectric and a non-ferroelectric material.