Strongly enhanced dielectric and energy storage properties in lead-free perovskite titanate thin films by alloying

Abstract

Lead-free perovskite oxide thin films prepared by alloying of titanates and materials with lower melting points are shown to have enhanced ferroelectric and dielectric properties. BaTiO3 (or SrTiO3) with 25% addition of BiFeO3 has much improved crystalline perfection because of the lower melting point of the BiFeO3 giving enhanced growth kinetics. The maximum dielectric peak temperature of BaTiO3 is increased by similar to 200 degrees C and leakage currents are reduced by up to a factor of similar to 100. The loss tangent reduces up to 300 degrees C, with a factor of > 14 reduction at room temperature. The dielectric breakdown strength is higher by a factor of similar to 3 (> 2200 kV cm(-1)) and from room temperature up to 500 degrees C the dielectric constant is > 1000. Also, a low variation of dielectric constant of similar to 9% from room temperature to 330 degrees C is obtained, compared to similar to 110% for BaTiO3. The maximum polarization (P-max) is double that of BaTiO3, at 125.3 mu C cm(-2). The film has high energy storage densities of > 52 J cm(-3) at 2050 kV cm(-1), matching Pb-based ferroelectric films. The strongly improved performance is important for applications in energy storage and in high temperature (up to 300 degrees C) capacitors as well as wider application in other electronic and energy technologies