Enhanced energy-storage performance of 0.94NBT-0.06BT thin films induced by a Pb0.8La0.1Ca0.1Ti0.975O3 seed layer

0.94(Na_0.5Bi_0.5TiO₃)-0.06BaTiO₃ ferroelectric thin films with and without the Pb_0.8La_0.1Ca_0.1Ti_0.975O₃ seed layer were deposited on platinum-buffered silicon substrates by using Sol–Gel process. The influence of Pb_0.8La_0.1Ca_0.1Ti_0.975O₃ seed layer and annealing temperatures on the microstructures, ferroelectric properties and energy-storage performances of the as-prepared films were investigated in details. The low annealing temperature and Pb_0.8La_0.1Ca_0.1Ti_0.975O₃ seed layer could improve the values of electric break-down field strength and P_max-P_r, which play a vital role for high recoverable energy-storage density. Owing to the high electric break-down field strength value of 3310 kV/cm, a large recoverable energy density of W=17.2 J/cm³ and a high energy efficiency of η=74.3% were obtained for the 0.94(Na_0.5Bi_0.5TiO₃)-0.06BaTiO₃ thin film with the Pb_0.8La_0.1Ca_0.1Ti_0.975O₃ seed layer, which was annealed at 450 °C.     

High recoverable energy storage density in (1-x)Bi0.5(Na0.8K0.2)0.5TiO3-xSrZrO3 thin films prepared by a sol-gel method

Lead-free (1-x)Bi_0.5(Na_0.8K_0.2)_0.5TiO₃-xSrZrO₃ (abbreviated as BNKT-100xSZ) thin films were deposited on Pt(111)/Ti/SiO₂/Si using sol-gel/spin coating method. With the addition of SZ, the long-range ferroelectric order dominant in BNKT is disrupted, which boosts the ferroelectric relaxor behavior. Consequently, a high recoverable energy density of 34.69?J/cm³ combined with an efficiency of 59.32% was achieved at the optimal composition of BNKT-15SZ under a high electric field of 2100?kV/cm, which can be ascribed to the slim P-E loops induced by strong relaxor behavior (γ?=?1.93) and the enhanced breakdown strength. Moreover, BNKT-15SZ thin film capacitor presents a good thermal stability with minimal variations of the energy density (<10%) and the energy storage efficiency (<5%) over a wide temperature range of 30–100?°C. The results indicated that the BNKT-100xSZ thin films may be a promising environmental-friendly material for energy storage applications.     

SrBi_2Ta_2O_9薄膜的制备和铁电性能研究

用一种新的低温过程制备了SrBi2Ta2O9铁电薄膜。在Sol-Gel方法中用Pt/Ti/SiO2/Si作衬底,研究了薄膜的结构和电特性。SrBi2Ta2O9薄膜在淀积Pt上电极之前和之后都要退火,第一次退火在760乇氧压下600℃时退火30分钟,在第二次退火后薄膜结晶良好。     

UV-Vis光谱研究Al3+,Zn2+,Cu2+掺杂对TiO2薄膜光学禁带宽度的影响

通过采用溶胶一凝胶法制备了稳定的TiO2溶胶，在此基础上制备了Al^3＋，Zn^2＋，Cu^2＋等金属离子氧化物掺杂的复合TiO2薄膜。采用X射线衍射、紫外一可见分光光度计以及NKD-7000W薄膜分析系统对所得薄膜晶相组成、光学性质以及禁带宽度等进行了表征。结果表明，这些金属氧化物与TiO2的复合薄膜体系中，形成了单一的锐钛矿相TiO2，与纯TiO2薄膜相比，复合薄膜中TiO2纳米粒子平均尺寸在一定程度上减小了。同时，复合TiO2薄膜的光学透过率以及光学禁带宽度均随着添加量的增加而规律性变化。     

Large electrostrain and high energy-storage of (1-x)[0.94(Bi0.5Na0.5) TiO3-0.06BaTiO3]-xBa(Sn0.70Nb0.24)O3 lead-free ceramics

(1-x)[0.94(Bi_0.5Na_0.5)TiO₃-0.06BaTiO₃]-xBa(Sn_0.70Nb_0.24)O₃ (abbreviated as BNTBT-100xBSN) lead-free ceramics were fabricated with a relative density greater than 96 %, and the structure as well as performance were tested. BNTBT-100xBSN ceramics are pseudo-cubic perovskite structure, with dense surface morphology. Doping BSN can effectively reduce the dielectric loss of ceramics and increase the relaxation properties to a certain extent. The randomly distributed ferroelectric phase was replaced by polar nano regions, thereby improving the electro-strain and energy storage performance of the system. The largest electro-strain and the corresponding normalized strain (d₃₃*) reach ~ 0.43 % and 633 pm/V respectively in the BNTBT-1BSN ceramic. The largest effective energy storage density reaching ~ 1.28 J/cm³ was tested in BNTBT-2BSN. BNTBT-100xBSN ceramics provide a feasible idea for the systematic research of lead-free ferroelectrics and improvements in electro-strain and energy storage applications.     

The phase formation process of Bi0.5(Na0.8K0.2)0.5TiO3 thin films prepared using the sol-gel method

Lead-free Bi_0.5(Na_0.8K_0.2)_0.5TiO₃ (abbreviated as BNKT) thin films were grown on Pt(111)/Ti/SiO₂/Si substrates using a sol-gel/spin coating technique and were then annealed at different temperatures (350 °C, 550 °C, 750 °C and 850 °C). Analysis of the XRD patterns and FT-IR spectra were used to determine the main reactions and the phase formation process of BNKT thin films during the sol-gel process. The results show that the dielectric constant of the thin films attains a maximum at a set temperature and then decreases at higher annealing temperatures, which can be attributed to phase formation and transformation. Moreover, the morphologies of the BNKT thin films improve with the increase in grain size and the formation of distinct grain boundaries. Furthermore, through increasing the pH of the precursor solutions, the size of the sol-gel colloidal particles increases slightly and the grains formed from the corresponding solutions tend to be small and uniform.     

Enhanced electrocaloric effect and energy-storage performance in PBLZT films with various Ba2+ content

(100)-oriented Pb_(0.90−x)Ba_xLa_0.10Zr_0.90Ti_0.10O₃ (x=0, 0.02, 0.05 and 0.11) antiferroelectric thick films were deposited on LaNiO₃/Si (100) substrates by the sol-gel process. The influences of Ba²⁺ content on the dielectric properties, electrocaloric effect (ECE), energy-storage performance and leakage current were systematically investigated. With Ba²⁺ content increasing, the temperature (T_m) corresponding to the maximum dielectric constant of the thick films was decreased, while their diffuseness was increased. The maximum ECE ∆T=18.1 °C was obtained in the thick film with x=0.05 at room temperature under ∆E=700 kV/cm. The maximum energy storage density of 42.3 J/cm³ and the corresponding efficiency of 68% was achieved in the film with x=0.11, companied by a power density of 0.53 MW/cm³, due to its high breakdown strength. In addition, a small leakage current density (<10⁻⁵ A/cm²) were attained in these films at room temperature. In conclusion, we believe that this kind of antiferroelctric thick film is a potential candidate for applications in solid cooling devices and the energy-storage systems.     

Structural peculiarities of 0.67 Pb(Mg1/3Nb2/3)O3–0.33 PbTiO3 thin films grown directly on SrTiO3 substrates

Growth of Pb(Mg_1/3Nb_2/3)O₃–33PbTiO₃ thin films by pulsed-laser deposition directly on non-conductive SrTiO₃ substrates for d₃₃-mode energy harvesters (EHs) was studied, as they offer a higher figure-of-merit than d₃₁-mode EHs. It was found that a high defect density, present in the film grown at 0.13?mbar, is manifested in the form of splitting of the (00l) peaks in X-ray diffraction, which was avoided by raising the process pressure to 0.27?mbar. Nevertheless, both films grow in a combined 2D and 3D manner, and form out-of-phase boundaries (OPBs) with a PbO rock-salt structure between the as-grown islands. It was found that the overall composition of the sample with optimized structural and functional properties was Pb_1.07Mg_0.19Nb_0.44Ti_0.32O₃, which is close to stoichiometric. The surplus of Pb is compensated by the formation of OPBs and Mg deficit maintains macroscopic electroneutrality. In-plane and out-of-plane relative permittivities of 1900 and 980, respectively, imply macroscopic out-of-plane polarization.     

Simultaneously enhanced energy storage density and efficiency in novel BiFeO3-based lead-free ceramic capacitors

In this work, a series of novel lead-free (1-x)Bi_0.83Sm_0.17Fe_0.95Sc_0.05O₃-x(0.85BaTiO₃-0.15Bi(Mg_0.5Zr_0.5)O₃) [(1-x)BSFS-x(BT-BMZ), x = 0.45?0.85] relaxor ceramics were prepared by solid phase sintering, and their dielectric properties and energy storage performances were explored. It was revealed that all the samples have a dense structure with pure pseudo-cubic phase. With the increase of x, the ferroelectric hysteresis loop is gradually slimmed accompanied by a decreasing polarization, indicating an enhanced relaxor behavior. Moreover, the electric breakdown strength increases linearly with x due to the fine grain size and enhanced relative density. Interestingly, a large recoverable energy density (～3.2 J/cm³) with an outstanding efficiency (～92 %) is achieved under an electric field ～206 kV/cm for the optimized component x = 0.75, which is superior to other reported lead-free ceramic systems. Moreover, the optimized ceramics of 0.25BSFS-0.75(BT-BMZ) show good thermal stability (25?100 °C) and excellent fatigue endurance (cycle number: > 10⁵) in energy storage performances. This work opens up a new route to tailor lead-free dielectric ceramics with high energy storage properties.     

TiO2多孔纳米薄膜的溶胶-凝胶法制备和光催化特性研究

锐钛矿型ＴｉＯ２多孔纳米薄膜可以从含聚乙二醇的钛醇盐溶前驱体中通过溶胶－凝胶法制备。涂层的形貌,如孔的大小和孔的分布可以通过聚乙二醇的加入量来控制。当聚乙二醇的加入量为０￣２．０ｇ时,孔径大小在０￣４００ｎｍ范围内变化。可见光透过光谱分析表明：随着ＴｉＯ２薄膜中气孔孔径增大,光的散射增强,透过率减小,该ＴｉＯ２镀膜玻璃对于紫外线具有吸收作用,有机磷农药敌敌畏水溶液在紫外灯照射和ＴｉＯ２多孔纳米薄膜