Effects Of Phase Transitions On Fluorescence Properties Of Rare Earth Ions Doped Ferroelectric Ceramics

Temperature is a significant physical quantity that can represent ferroelectric properties, so measurement of phase-transition temperature accurately is vital to improve ferroelectric properties. In recent years the method has attract considerable attentions of using fluorescence to indicate phase transition temperature through doping rare earth ions into ferroelectric ceramics, for the change of fluorescence spectra induced by phase transition can indicate phase transition temperature accurately. This method has several advantages, such as noncontact, simplicity, and so on. At present, this fluorescence method is still in its infancy, so it’s necessary to study it more detailedly. We have systematically carried out the investigation about the effect of phase-transition on fluorescence properties based on the Er³⁺ ions doped BaTi O₃（BT） ceramics, Ba_0.77Ca_0.23 Ti O₃（BCT） ceramics and K_0.5Na_0.5Nb O₃（KNN） ceramics.The measurement of phase-transition temperature in 1% Yb³⁺,1% Er³⁺:BT ceramic has been designed and accomplished. The pure BT ceramic and 1%Yb³⁺,1% Er³⁺:BT ceramic have been prepared by Sol-Gel method. The ferroelectric properties and dielectric properties have been measured, it is found that the rare earth ions improved the ferroelectric properties of the sample, and the Curie temperature（TC） is raised to 136 °C meanwhile the orthogonal-tetragonal phase transition temperature（TO-T） is reduced to-11 °C. The effect of temperature on fluorescence properties between-50 °C to 150 °C has been studied, and the upconversion（UC） fluorescence were originated from 4S3/2â†'4I15/2 transitions of Er³⁺ions. It is found that the fluorescence intensity and peak position have changed, and some Stark peaks have disappeared near TC and TO-T. The result illustrates that the TC and TO-T can be achieved by using the fluorescence method in BT-based ceramics.The measurement of phase-transition temperature in 1% Er³⁺: BCT ceramic has been designed and investigated. The pure BCT ceramic and 1% Er³⁺: BCT ceramic have been prepared by Sol-Gel method. The ferroelectric properties and dielectric properties have been measured, it is found that the Er³⁺ ions greatly improved the ferroelectric properties of the sample, and the TC is raised to 110 °C. The effect of temperature on fluorescence properties between 90 °C to 150 °C have been studied,and the UC fluorescence were originated from 4S3/2â†'4I15/2 transitions of Er³⁺ ions. It is found that the fluorescence intensity and peak position have changed near TC. The result illustrates that the TC can be achieved by using the fluorescence method in BCT-based ceramics.The measurement of phase-transition temperature in 1% Er³⁺:KNN ceramic has been designed and investigated. The pure KNN ceramic and 1% Er³⁺:KNN ceramic have been prepared by high temperature solid-state reaction. The ferroelectric properties and dielectric properties have been measured, it is found that the Er³⁺ ions improved the ferroelectric properties of the sample, and the TC is reduced to 404 °C and the TO-T is reduced to 201 °C. The effect of temperature on fluorescence properties between 150 °C to 450 °C has been studied, and the UC fluorescence were originated from 2H11/2â†'4I15/2 and 4S3/2 â†' 4I15/2 transitions of Er³⁺ ions. It is found that the fluorescence intensity and fluorescence intensity ratio have changed near TC and TO-T. The result illustrates that the TC and TO-T can be achieved by using the fluorescence method in KNN-based ceramics.