Research On Luminescent Properties Of Rare Earth Doped Potassium Sodium Niobate-based Ceramic Materials

With the rapid progress and development of human society,science and technology have begun to establish the concept of protecting the environment and sustainable development,and people have accelerated the pace of exploring environmentally-friendly functional materials.Rare earth element-doped niobate-based inorganic ferroelectric materials not only effectively enhance electrical properties,but also introduce unique optical properties,and their luminescence intensity can be modulated based on photochromic reactions.It has potential application value in the fields of biological imaging,anti-counterfeiting,and optical information storage in modern scientific and technological life.Therefore,this versatile intelligent ferroelectric material has a very good application prospect.This thesis focuses on the research of doping rare earth elements in KNN-based lead-free ferroelectric ceramic materials,exploring its preparation process and discovering various optical characteristics,such as test light.Modulation of color change reaction and reversible fluorescence.The main research objects are the following two:the up-conversion luminescence,photochromism,and temperature sensing characteristics of Pr³⁺and Yb³⁺ions co-doped into KNN-based ceramic materials;the research of K_xNa_1-xNbO₃:Pr³⁺ferroelectric ceramic materials Luminescence,photochromic reaction and luminous modulation.In the work of KNN:x Pr³⁺/0.01Yb³⁺,we synthesized all sample ceramics by the traditional solid-phase sintering.These ceramics have an up-conversion luminescence phenomenon under the excitation of a 980 nm diode laser and the color is depened on the sample surface under the irradiation of visible light.The photochromic phenomenon of obvious darkening,the up-conversion luminous intensity of the sample can be effectively controlled based on the photochromic reaction,and the up-conversion luminous intensity is significantly attenuated after irradiation,up to 74.94%.In addition,the color of the sample will be completely restored to its original state by thermal stimulation upon the sample,and the luminous intensity will not fluctuate greatly by alternating irradiation and heating stimulation cycle test,illustrating a has good fatigue resistance.In the temperature range of 123-573 K,the optical temperature sensing characteristics of the samples were also tested,irradiated and unirradiated.It was found that the prepared samples had stable and wide-range temperature sensing performance.These results show that KNN:x Pr³⁺/0.01Yb³⁺is expected to be applied in the market of optical energy storage,thermometer and sensor applications.The ferroelectric(K_xNa_1-x)NbO₃was selected as the host,and the rare earth Pr³⁺ions were doped.For the first time,various applications such as photoluminescence,photochromism,luminescence modulation,and thermoluminescence have been realized in Pr³⁺-doped(K_xNa_1-x)NbO₃ferroelectric ceramics.All samples showed intense red light emission centered at 610 nm under excitation at 337 or 448 nm.With the increase of K⁺content,the photochromic reaction also increases.And the best photochromic reaction phenomenon was found in(K_0.5Na_0.5)NbO₃:Pr³⁺ceramics.The sample can achieve stable photoluminescence modulation,with a maximum ratio of50.71%before and after irradiation.In addition,all prepared ceramics can show visible thermoluminescence.And the luminous intensity decreases with the increase of K⁺content.In combination with two kinds of performance changes,we discuss the mechanism of luminous modulation and thermoluminescence.Current research can provide a workable paradigm to achieve multiple optical properties in one material.