Structure, dielectric tunability, thermal stability and diffuse phase transition behavior of lead free BZT-BCT ceramic capacitors

This paper reports the development of a lead free {Ba(Zr0.2Ti0.8)O-3}((1-x)){(Ba0.7Ca0.3)TiO3}(x) - x=0.10, 0.15 and 0.20 - BZT-BCT ceramic solid solution system prepared using a solid-state reaction technique. The evolution of the Raman spectra with temperature was used to study the variation of the basic phase transition of BaTiO3 in these compositions. The phase transition temperature on heating was found to decrease to 310 K, 300 K, and 300 K, respectively, with increasing Ca content on BCT end and decreasing Zr content on BZT end of lead free pseudobinary ferroelectric BZT-BCT system. Tetragonal and rhombohedral phase coexistence is observed at room temperature from X-ray diffraction (XRD) spectra. Rhombohedral phase is identified between the 83 K and 273 K from temperature dependent Raman studies. Raman results are in excellent agreement with those obtained from temperature dependent dielectric measurements. Bulk ceramic BZT-BCT materials have shown interesting temperature dependent dielectric properties and as well as higher values of room temperature dielectric constant similar to 7800, 8400, 5200, dielectric tunability similar to 82%, figure of merit (FOM) similar to 93.71 % with low dielectric loss (tan delta) similar to 0.015 to 0.024 and good thermal stability at high sintering temperature (1600 degrees C); they might be one of the strong candidates for dielectric tunable capacitor applications in an environmentally protective atmosphere. (C) 2012 Elsevier Ltd. All rights reserved.