LINEAR THERMAL EXPANSION OF 0.5BA(ZR0.2TI0.8)O3-0.5(BA0.7CA0.3)TIO3 BULK CERAMIC

We report the linear thermal expansion coefficient of lead-free ferroelectric ceramic barium zirconate titanate - barium calcium titanate 0.5Ba(Zr0.2Ti0.8)O-3-0.5(Ba0.7Ca0.3)TiO3 (BZT-BCT). The material was prepared by solid-state synthesis and consolidated by sintering at 1450 degrees C. BZT-BCT crystallizes in the perovskite phase. The microstructure of the ceramic with about 95 % relative density consists of about 10 mm-sized grains. The contact dilatometry of the ceramic specimen reveals the change of slope of the linear thermal expansion curve at 84 degrees C. This is in good agreement with the peak of the dielectric permittivity versus temperature at about 85 degrees C indicating the transition from the low-temperature polar ferroelectric phase to a high-temperature nonpolar phase or Curie temperature. The thermal expansion coefficients of the polar tetragonal and nonpolar cubic phases of BZT-BCT are 7.69x10(-6) K-1 (40 degrees C - 80 degrees C) and 12.39x10(-6) K-1 (100 degrees C - 600 degrees C), respectively. The thermal expansion data are among the material data needed in the design of thin- and thick-film structures for energy-harvesting and energy-storage applications.