Investigation On Photoluminescence Property Of Rare Earth Doped Titanates Lead-Free Piezoelectric Ceramics

In recent years, Rare-earth-doped lead-free piezoelectric ceramics as a candidate for ferro-/piezoelectric and luminescent multifunctional materials have received much attention due to its widely applications in detectors, sensors and display devices. It is well known that rare earth doping piezoelectric materials can not only help enhance the piezoelectric property, but also possible to obtain excellent photoluminescence property. However, the coupling effects between photoluminescence and different circumstance, such as, compositional change, temperature and electric field, have been seldom reported. Thus, piezoelectric/photoluminescence multifunctional material is designed on the base of Er3+-doped (Ba,Ca)(Zr,Ti)O3 ceramics and the dependence of photoluminescence on compositional change, temperature and electric field is reported in this work. The main search contents are as follows:(1) The influence of Ca contend on photoluminescence property of Er3+-doped (Ba1-xCax)(Zr0.1Ti0.9)O3 lead free ceramics.Er3+-doped (0.5 mol%) lead-free (Ba1-xCax)(Zr0.1Ti0.9)O3 dense ceramics, synthesized via a sol-gel synthesis route and a ceramic sintering process, possess excellent piezoelectric/photoluminescence performance, which is sensitive to compositional changes. It is clear that both the d33 and kp increased gradually and then decreased with increasing x, the optimal piezoelectric properties can be obtained at x = 0.15. With an increase in x, the upconversion emission intensities first increased and then decreased rapidly, giving the maximum value at x= 0.15, which agrees well with the piezoelectric and dielectric behavior. Thus, it is possible to indicate the compositional changes of piezoelectric ceramics through measuring the photoluminescence in rare earth doped piezoelectric ceramic.(2) The influence of temperature on photoluminescence property of Er3+-doped (Ba0.97Ca0.03)(Sn0.06Ti0.94)O3 lead free ceramics.Er3+-doped ferroelectric (Ba0.97Ca0.03)(Sn0.06Ti0.94)O3 (BCST-Er) ceramics were prepared by a conventional solid-state reaction technique. The dielectric constant and ferroelectric polarization-electric fields hysteresis loops of the BCST-Er ceramic as a function of temperature were measured, and the Curie temperature was confirmed to be 353 K. Also, the temperature dependence on the luminescent emission peak intensity of 525 nm was investigated. With increased temperature, the luminescent peak intensity of 525 nm shows a gradual increase at first, thereafter exhibits a decreasing trend and maximizes at a Tc of～353 K. Therefore, the ultrahigh luminescent emission near Tc can be used a probe for ferroelectric Curie phase transition, which posses the advantage of noncontact and quick response.(3) The influence of electric field on photoluminescence property of Er3+-doped (Ba0.95Sr0.005)(Zr0.1Ti0.9)O3 lead free ceramics.The 0.2 mol% Er3+-doped (Ba0.95Sr0.05)(Zr0.1Ti0.9)O3 (BSZT:Er) ceramics were prepared via a conventional solid-state reaction method. With increased polarization electric field (E) from 0 to 4.5 kV/mm, the photoluminescence intensity at 550 nm exhibits an increasing trend, giving the maximum value at E= 4.5 kV/mm. After undergoing a polarization treatment E= 4.5 kV/mm, the enhancement of photoluminescence at 550 nm reach a plateau followed a constant value of-6 times. An excellently linear relationship between d33 and IE/Io of BSZT:Er is observed. The results suggest that the good relationship between d33 and IE/Io of BSZT:Er is potential in optically monitoring the piezoelectric constant d33 and designing piezoelectric/luminescent multifunctional devices.