Dengfeng Peng

Strong red emission in Pr doped (Bi0.5Na0.5)TiO3 ferroelectric ceramics

The photoluminescence of Pr doped (Bi0.5Na0.5)TiO3 ferroelectric ceramics prepared by conventional solid-state reaction were investigated. A bright red emission is observed at room temperature, which ascribed to 1D2→3H4 transition. The excitation bands are mainly located at 440 ∼ 505 nm, which is adaptable to the emission band of commercial blue light-emitting diodes (LEDs) chips. The optimal emission intensity was also obtained when Pr doping level was 0.003 mol. Meanwhile, the enhanced ferroelectric properties were obtained by Pr doping. The results show that Pr doped (Bi0.5Na0.5)TiO3 ceramics as a multifunctional material may be useful for white LEDs, sensor, and optical-electro integration.

Green and red emission for (K0.5Na0.5)NbO3:Pr ceramics

The photoluminescence properties of Pr-doped K0.5Na0.5NbO3 (KNN) ceramics were prepared by the solid-state reaction method and investigated as a function of Pr concentration and sintering temperature. The excitation band ranging from 430 to 500 nm covers the emission wavelength of all commercial blue light-emitting diode chips. The photoluminescence spectra of KNN:Pr exhibit strong green (528 nm) and red (617 nm and 650 nm) emissions. The optimum doping concentration of Pr in KNN is 0.5 mol. %, and the optimized sintering temperature is 1170 °C. In addition to the admirable intrinsic piezoelectric properties of KNN, Pr-doped KNN may take an important role in many fields as a multifunctional material.

Upconversion luminescence, ferroelectrics and piezoelectrics of Er Doped SrBi4Ti4O15

Er3+ doped SrBi4Ti4O15 (SBT) bismuth layered-structure ferroelectric ceramics were synthesized by the traditional solid-state method, and their upconversion photoluminescent (UC) properties were investigated as a function of Er3+ concentration and incident pump power. Green (555 nm) and red (670 nm) emission bands were obtained under 980 nm excitation at room temperature, which corresponded to the radiative transitions from 4S3/2, and 4F9/2 to 4I15/2, respectively. The emission color of the samples could be changed with moderating the doping concentrations. The dependence of UC intensity on pumping power indicated a two-photon emission process. Studies on dielectric properties indicated that the introduction of Er increased the ferroelectric-paraelectric phase transition temperature (Tc) of SBT, thus making this ceramic suitable for piezoelectric sensor applications at higher temperatures. Piezoelectric measurement showed that the doped SBT had a relative higher piezoelectric constant d33 compared with th...

Polarization-induced enhancement of photoluminescence in Pr3+ doped ferroelectric diphase BaTiO3-CaTiO3 ceramics

Photoluminescence (PL) spectra impacted by electric polarization in Pr3+ doped diphase (1-x)BaTiO3-xCaTiO3 (x = 0.4–0.7) ceramics were studied systematically. The transparent electrode of indium tin oxide was deposited on both surfaces of ceramics to reduce experimental errors and then PL properties were characterized with and without polarization. An enhancement in PL intensity of ∼100% was obtained in the Ba1−xCaxTiO3 (x = 0.7) ceramics with polarization. It was found that the PL intensity increased the same level whether the poling direction was up or down. With the x increases, the enhanced factor decreased first and then increased, which ascribed to the ratio of the tetragonal Ba0.77Ca0.23TiO3 and orthorhombic Ba0.1Ca0.9TiO3 in the diphase ceramics. The investigation of UV-Vis reflective spectrum and X-ray Photoelectron Spectroscopy spectrum demonstrated that the polarization effect on the PL was attributed to the change of band gap of host by a local electric field around Pr3+ doped in Ba0.1Ca0.9TiO...

Bright upconversion luminescence and increased Tc in CaBi2Ta2O9:Er high temperature piezoelectric ceramics

Er3+ doped CaBi2Ta2O9 (CBT) bismuth layered-structure high temperature piezoelectric ceramics were synthesized by the traditional solid state method. The upconversion (UC) emission properties of Er3+ doped CBT ceramics were investigated as a function of Er3+ concentration and incident pump power. A bright green upconverted emission was obtained under excitation 980 nm at room temperature. The observed strong green and weak red emission bands corresponded to the transitions from 4S3/2 and 4F9/2 to 4I15/2, respectively. The dependence of UC emission intensity on pumping power indicated that a three-photon process was involved in UC emissions. Studies of dielectric with temperature have also been carried out. Introduction of Er increased the Curie temperature of CBT, thus, making this ceramic suitable for sensor applications at higher temperatures. Because of its strong up-converted emission and increased Tc, the multifunctional high temperature piezoelectric ceramic may be useful in high temperature sensor,...

Luminescent, dielectric, and ferroelectric properties of Pr doped Bi7Ti4NbO21 multifunctional ceramics

Pr doped Bi7Ti4NbO21 (BTN) multifunctional ceramics were prepared by a conventional sintering technique and their luminescent, dielectric, and ferroelectric properties were investigated. The X-ray diffraction data showed that the samples were single phase, and the scanning electron microscopy image indicated that the ceramics had flake-like grains with uniform thickness. The red emission was observed under the ultraviolet and blue light excitation at room temperature. The thermal quench of luminescence was measured and the result indicated that Pr doped BTN ceramics might be potentially applied in luminescent probes and temperature sensors. With the increasing Pr3+ content, the intensity of the photoluminescence increased initially and then decreased due to concentration quenching; The Curie temperature Tc was slightly shifted to the lower temperature; the ferroelectric properties was almost unchanged by doping. As a new multifunctional material, the Pr doped BTN ceramics could be used for a wide range of application, such as integrated electro-optical devices.

Up-conversion luminescence of Er3+ and Yb3+ co-doped CaBi2Ta2O9 multifunctional ferroelectrics

Er3+ and Yb3+ co-doped CaBi2Ta2O9 (CBT)-based bismuth layered-structure oxides were synthesized by a simple solid-state reaction method. Their up-conversion (UC) luminescence, dielectric and ferroelectric properties were investigated. Two strong green emission bands centered at 526 and 547 nm and a weak red emission band centered at 658 nm were obtained under a 980 nm laser excitation at room temperature. These emission bands originated from the radiative relaxation of Er3+ from 2H11/2, 4S3/2, and 4F9/2 levels to the ground state 4I15/2, respectively. At the meantime, the fluorescence intensity ratio (FIR) variation of two green UC emissions at 526 and 547 nm has been studied as a function of temperature in the range of 153–603 K. The maximum sensor sensitivity obtained was 39 × 10-4 K-1 at 590 K, which indicated that Er3+/Yb3+ co-doped CBT ceramic is a promising candidate for applications in optical high temperature sensor.

Photoluminescence and thermal stability of yellow-emitting Pr3+ doped CaAl2O4 phosphors

Pr3+-doped CaAl2O4 phosphors with broad yellow emission were synthesized by conventional solid-state reaction in air and their structural and luminescent properties were investigated. A pure monoclinic structure can be obtained when the sintering temperature is 1400°C or above. With photoluminescence (PL) measurement, the excitation was observed at 450–500 nm, which covered the emission of the blue light-emitting diode (LED) chips. Emission of the phosphors showed a green band and a red band. So these phosphors showed great potential in application of warm white LEDs without reabsorption. Additionally, the optimal emission intensity was obtained when Pr doping level was at 0.2 mol%. Furthermore, the Pr-doped CaAl2O4 phosphors have the higher quenching temperature. With an increase in temperature, the emission bands of Pr-doped CaAl2O4 showed an abnormal blue-shift.