High energy storage density achieved in Bi3+-Li+ co-doped SrTi0.99Mn0.01O3 thin film via ionic pair doping-engineering

The demand for lead-free dielectric capacitors with rapid charge-discharge ability and high energy storage density is increasing owing to the rapid development of electronic equipment. Lead-free Sr1-x(Bi0.5Li0.5)xTi0.99Mn0.01O3 (x = 0.02, 0.025, 0.03, 0.035) thin films grown on Pt/Ti/SiO2/Si substrates were prepared by sol-gel method. A huge enhancement in polarization was found in Bi3+-Li+ co-doped SrTiO3 thin films. The large lattice distortion and local broken-symmetry due to formation of Bi3+-Li+ ionic pairs are responsible for ferroelectricity and high polarization. The maximum polarization (42.1 μC/cm2) and largest energy storage density of 47.7 J/cm3 at 3307 kV/cm were both achieved in Sr0.975(Bi0.5Li0.5)0.025Ti0.99Mn0.01O3 thin film. Moreover, an excellent temperature-dependent stability was also obtained in Sr0.975(Bi0.5Li0.5)0.025Ti0.99Mn0.01O3 thin film from 30 to 110 °C.