Effects of gadolinium modification on leakage conduction and energy storage performance of sol-gel derived (Ba0.85Ca0.15)(Zr0.2Ti0.8)O3 thin films

The microstructures, leakage conduction and energy storage performances of Gadolinium (Gd 3+ ) modified barium calcium zirconate titanate based thin films [Ba (0.85-x) Ca 0.15 Gd x ][Zr 0.2 Ti 0.8 ]O (3+0.5x) ( x = 0, 0.005, 0.0075 and 0.01) prepared on the Pt/Ti/SiO 2 /Si substrates using sol-gel method were characterized and analyzed. The dense and uniform microstructure with fine nanocrystalline grains is obtained in low Gd 3+ concentration ( x ≤ 0.0075) doped BCGZT thin films with single phase perovskite structure. With the increase of Gd 3+ content, the leakage current density of BCGZT films initially decreases to the minimum at x = 0.0075 due to the existing of defect dipoles V Ca ″-V O •• caused by the Gd 3+ substitution for A site ions and then increases significantly due to the appearance of impurity phases. With the increase of electric field, the leakage mechanism for each BCGZT film transforms from ohmic conduction and/or SCL conduction to F-N tunneling. The remanent polarization keeps decreasing because of the weakened ferroelectricity of Gd 3+ modified BCZT perovskites and the decreasing average grain size as the Gd 3+ content increases. The BCGZT thin film with x = 0.0075 possesses an enhanced energy storage density of 55.1 J/cm 3 and an acceptable energy storage efficiency of 67.1 % at the ultra-high breakdown field of 4300 kV/cm, which is promising for capacitor applications.