High energy storage efficiency and thermal stability of A‐site‐deficient and 110‐textured BaTiO₃–BiScO₃ thin films

Abstract

The development of thin film dielectrics having both high energy density and energy conversion efficiency, as well as good thermal stability, is necessary for practical application in high‐temperature power electronics. In addition, there is a demand for the development of new Pb‐free high‐energy density dielectric materials due to environmental concerns. In this regard, thin films of weakly coupled relaxors based on solid solutions of BaTiO3–BiMeO3 have shown good promise, because they exhibit a remarkably large polarization over a wide temperature range. Nevertheless, the performance of Pb‐free thin films has lagged behind that of their Pb‐based counterparts in terms of thermal stability and energy conversion efficiency. Toward this end, most recent studies on BaTiO3–BiMeO3 systems have focused on the optimization of material composition, while relatively less attention has been paid to other aspects such as defect chemistry and crystallographic texture. In this study, we examine the effects of A‐site vacancy and crystallographic texture on the energy storage performance of BaTiO3–BiScO3 thin films synthesized using pulsed laser deposition (PLD). It is shown that a high energy storage density (Wr) of ~28.8 J/cm3 and a high efficiency of η >90% are achieved through a combination of moderate A‐site vacancy concentration and (110) crystallographic texture. Furthermore, Wr remains nearly temperature independent while a high efficiency of η >80% is maintained for temperatures up to 200°C, which constitutes one of the best performances for Pb‐free ferroelectric films for high‐temperature capacitor applications.

Temperature‐induced changes of the electrical and mechanical properties of aerosol‐deposited BaTiO3 thick films for energy storage applications

“…For comparison, an overview of dielectric properties in commercially available capacitors and selected lead‐free dielectric materials is provided in Table 2. The synthesis temperature ( T S ) of the AD method is at room temperature, much lower than that of solid‐state reaction for the fabrication of commercial X7R multilayer ceramic capacitors (MLCCs) and other BT‐based ceramic capacitors 55–65 . It should be mentioned here that annealing at 500°C is required for AD‐BT films.…”

“…The synthesis temperature (T S ) of the AD method is at room temperature, much lower than that of solid-state reaction for the fabrication of commercial X7R multilayer ceramic capacitors (MLCCs) and other BT-based ceramic capacitors. [55][56][57][58][59][60][61][62][63][64][65] It should be mentioned here that annealing at 500 • C is required for AD-BT films. In addition, the annealed AD-BT films exhibit high energy storage density and efficiency mainly due to the high electrical breakdown strength (E BDS ) and slim-like polarization loop.…”

Critical Effect of Film–Electrode Interface on Enhanced Energy Storage Performance of BaTiO3–BiScO3 Ferroelectric Thin Films

“…It shows that the Pt layer in both the samples has a (200) orientation, in accordance with X-ray diffraction results from our previous work. 14 However, the crystallinity of the film layer immediately adjacent to the Pt-electrode is markedly different for the two samples. We observed a defective layer at the film− electrode interface of the BSBT 510 °C sample, which has an amorphous structure and varied thicknesses from region to region along the entire interface (see Figure 1).…”

“…41 For example, Funakubo et al demonstrated that independent of the other parameters (i.e., composition, film thickness, and Pt-orientation), the temperature-dependent growth rate (V) of PZT films follow the V 100 > V 110 > V 111 sequence. 42 Here, for the BSBT 510 °C sample, since the crystalline layer in the bulk film grows on top of the interfacial amorphous layer, the film exhibits a (100) growth texture, 14 which is dictated by the lower PD of the (100) planes.…”

“…17 Third, it remains a challenge to grow highly textured perovskite ferroelectric thin films directly on a Pt-coated Si substrate, 18,19 which is important for achieving higher dielectric properties and novel functionalities. 14 Previous studies have shown that the various limitations of Pt-electrodes, as mentioned above, can be attributed to interlayer diffusion during thin-film deposition. For instance, hillock formation is caused by the diffusion of Ti from the underlying Ti or TiO 2 adhesion layers into the Pt-electrode, which forms TiO x inside the Pt-electrode.…”