Preparation And Electrical Properties Of Strontium-based Amorphous Films And Polycrystalline Ceramics

Amorphous film is also called amorphous film.Due to amorphous film has small limitation on substrate material,larger performance development possibility and simple preparation process,the most of researches on functional materials are converte single crystal and polycrystalline materials to amorphous materials now.Information storage and energy storage is also particularly important research areas in the 21st century,where science and technology are rapidly developing and resources are scarce.In this paper,the srtrontium-based thin film memristor was prepared by sol-gel method.The chemical state,leakage current performance,resistance swithching effect and conduction mechanism of the srtrontium-based amorphous film were studied.In addition,the srtrontium-based lead-free ferroelectric ceramics were prepared by high-temperature solid-state reaction method.The dielectric properties,electrocaloric effect,pyroelectric energy harvesting and energy storage performances were studied.?1?High temperature annealed Au/SrTiO₃/Si?100?and low temperature annealed Au/SrTiO₃/FTO/Glass devices were prepared by sol-gel method.The combination of chemical components and leakage current performance,conduction mechanism,and resistive performance of SrTiO₃ films under different crystal states were studied.The resistance switching effect of SrTiO₃ film annealed at 400°C is the best,the high and low resistance ratios are 10².In addition,Ohmic conduction became dominated in initial high-and low-resistance state,however,space charge limited conduction mechanism was dominant in later high-resistance field.The resistance switching effect in the device was explained by formation and rupture of oxygen vacancies interrelated filament well.?2?Layered perovskite structure SrO?SrTiO₃?_n?n=1 and 2?thin films with different compositions were prepared by sol-gel method under 500°C.The SEM and XPS analysis of SrO?SrTiO₃?_n films were performed.Leakage current,conduction mechanism and resistance switching performances of SrO?SrTiO₃?_n films were studied.The SrO?SrTiO₃?₁ film exhibits a diode characteristic,and the leakage current conduction mechanism results indicate that the diode effect is related to the Schottky emission mechanism.The test results of the resistive effect show that the higher the SrO ratio,the more obvious the resistive property of the film,and the high-and low-resistance state of the device has good retention and fatigue resistance.?3?SrFe_0.1Ti_0.9O₃ films were prepared by sol-gel method under different annealing temperature?400,500,600 and 700°C?.The results show that the films exhibit a characteristic diode effect under annealing temperatures.In addition,the leakage current density is smaller in the low-temperature annealed film and is related to the compactness of the amorphous film.In addition,the sample annealed at 500°C shows a better resistance switching effect,the high and low resistance ratio can achieve 10³,and the 500°C leakage current conduction mechanism is also dominated by the Schottky emission mechanism at the high-voltage range.This conduction mechanism proves the oxygen vacancies are related to resistive performance.?4?Amorphous double perovskite structure Bi₂FeCrO₆ films were prepared by sol-gel method at different annealing temperatures?400,450,500 and 550°C?.The XPS results show that there are two valence states of Fe in the film,and Bi exists only in the 4⁺valence state,and Cr is present in the film as an oxide and a compound.The thicknesses of amorphous Bi₂FeCrO₆ films were observed to be approximately 250 nm from the cross-sectional SEM images.In addition,the resistive properties of amorphous Bi₂FeCrO₆films annealed at 400,450 and 500°C are significantly better than those of 550°C annealed films.Finally,it is proved that the conduction mechanism conversion in the film is closely related to the accumulation of oxygen vacancies.?5?We prepared polycrystalline Sr_xBa_1-xNb₂O₆?x=0.4,0.5 and 0.6?ceramics by solid-state reaction route.XRD results show that the Sr_xBa_1-xNb₂O₆ ceramic is a tungsten bronze structure.The high temperature dielectric properties of the sample show a relaxation phase transition behavior similar to that at low temperatures.This behavior is considered as high temperature dielectric relaxation which is independent of phase transition.We also analyzed the electrocaloric effect,thermal energy harvesting,and energy storage performance of the ceramic based on the measured hysteresis loop.At 60 kV·cm^-1,?S_max and?T_max of SBN60ceramics at Curie temperature are 0.39 J·Kg^-1·K^-1 and 0.32 K,respectively.The SBN60 has a maximum pyroelectric collection density of 170 kJ·m^-3 and a temperature range of 293 to433 K.The storage density and efficiency of SBN60 at room temperature were 0.19 J·cm^-3and 86.37%,respectively.The above results show that Sr_xBa_1-xNb₂O₆ ceramics have great potential in environmental energy conversion and harvesting loss heat energy.