A novel green emitted phosphor Li2Sr1−xBaxSiO4:Eu2+ (LSBS:Eu) has been synthesized by a solid-state reaction method. Its crystal structure and grain morphology have been investigated by a powder X-ray diffractometer and a scanning electronic microscope, respectively. A green emission peak around 566 nm was observed under the excitation ranged from 225 to 500 nm, which covers the emission spectra of blue and near UV LEDs. The optimal emission intensity was obtained when the Ba content was 0.6 and Eu2+ doping level was 0.003 mol. Furthermore, the investigation of the temperature dependence of luminescence and quantum efficiency indicate that LSBS:Eu phosphors are highly thermally stable and energy saving. The lifetime decay curves and chromaticity coordinates were also obtained. The results show that Li2Sr1−xBaxSiO4:Eu2+ would be a promising green phosphor candidate for UV-chip-based multiphosphor converted white LEDs.

Ho3+/Yb3+-codoped ZnWO4 phosphors were synthesized using a solid state reaction method and their structures, upconversion (UC) luminescence, and temperature-sensing properties were investigated. The obtained ZnWO4:0.01Ho3+/xYb3+ phosphors crystallized in the monoclinic phase with space group P2/c. Under 980 nm excitation, bright green [(5F4, 5S2) → 5I8], weak red (5F5 → 5I8), and near-infrared emissions [(5F4, 5S2) → 5I7] were observed. The optimal Ho3+ and Yb3+ doping concentrations in ZnWO4 were 0.01 and 0.15, respectively. The near-infrared-green (I757/I540) and red-green (I641,665/I540,549) fluorescence intensity ratios (FIRs) were studied as a function of temperature at 83–503 K. The sensitivity of the ZnWO4:0.01Ho3+/0.15Yb3+ phosphors was also discussed and their potential application as thermal sensors in luminescence thermometry was analyzed using a four-level system and the intensity ratio of the red and green emissions. ZnWO4:0.01Ho3+/0.15Yb3+ phosphors could potentially be applied as optical temperature-sensing materials.

Ferroelectric (1 − x)BaTiO3-x(Na0.5Ho0.5)TiO3 ceramics with ferroelectric and up-conversion luminescent multifunctions were designed and fabricated by a solid state reaction process. Their structure, ferroelectric, piezoelectric, up-conversion photoluminescence and relative optical temperature sensing properties were investigated systematically. Crystal structure analysis and Rietveld refinements based on the powder X-ray diffraction data show that the ceramics crystallized in the tetragonal perovskite space group P4mm at room temperature. Enhanced electrical properties and strong green up-conversion luminescence with thermally coupled green emission bands centered at 523 and 553 nm were observed. For a typical sample x equals 0.05, a large electrostrain of 0.279% was obtained under a 70 kV cm−1 electric field that is comparable to that of the PZT4. Meanwhile, the excellent optical temperature sensitivity (0.0063 K−1 at 480 K) is higher than that of Er-doped BaTiO3 nanocrystal materials. The results suggest that the BaTiO3-(Na0.5Ho0.5)TiO3 material should be an attractive material for piezoelectric actuator and temperature sensing device applications.

•(Sr,Ca,Ba)2SnO4:La,Sm were prepared by solid-state reactions.•ML and PL spectra, and thermoluminescence properties were investigated.•Emission ascribe to the 4G5/2 to 6HJ (J = 5/2, 7/2, 9/2, 11/2) transitions of Sm3+.•Traps are tuned in both trap depth and quantity.•Traps are ameliorated in both trap depth and quantity by Ca2+ and Ba2+ substitution for Sr2+ and La3+ co-doping with Sm3+.(Sr,Ca,Ba)2SnO4:Sm3+,La3+ phosphors were prepared by traditional solid-state reactions. Based on previous Sr2SnO4:Sm3+ phosphor, mechanoluminescence (ML) property was greatly enhanced by substitution of Ca2+, Ba2+ and codoped of La3+. Among the samples, (Sr0.7Ca0.27Ba0.03)1.92La0.06Sm0.02SnO4 showed excellent properties with intense ML and good linearity between the intensity and the load. ML spectrum of (Sr0.7Ca0.27Ba0.03)1.92La0.06Sm0.02SnO4 is consistent with the PL spectrum, ascribed to the 4G5/2 to 6HJ (J = 5/2, 7/2, 9/2, and 11/2) transitions of Sm3+ ions. Introducing Ca2+, Ba2+ and La3+ causes more lattice distortion or defects in the crystal grains, indicating traps can be controlled in both trap depth and quantity. Due to the improvement of traps in the system, ML performance is enhanced.

•The Er-doped (Ba0.4Ca0.6)TiO3 diphase ceramics were prepared by a solid state reaction method.•The dual-mode photoluminescence properties were observed.•The good optical temperature sensing performance was obtained.•The Er doping enhances ferroelectric properties and modifies dielectric properties.Dual-mode phosphors, Er3+ doped Ba0.4Ca0.6TiO3 ferroelectric diphase ceramics, were prepared by a conventional solid-state reaction method and their phases, microstructure, photoluminescence, ferroelectric and dielectric properties were investigated. The ceramics exhibit up-conversion and down-conversion emission of 550 nm light excited by a near-infrared (980 nm) light and a 487 nm blue light, respectively. The related photoluminescence mechanism has been discussed. In up-conversion emission, the 2H11/2 → 4I15/2 and 4S3/2 → 4I15/2 transitions of the Er3+ ion portray a temperature dependent behavior and have been used for optical temperature sensor using the fluorescence intensity ratio method. The maximum sensitivity is found to be 0.0033 K−1 at 483 K in the temperature range of 103–573 K. Together with the enhanced ferroelectric properties and good dielectric properties, these ceramics should be one of the promising candidates for multifunctional optoelectronic applications.

Er3+ doped K0.5Na0.5NbO3 (KNN) lead-free piezoelectric ceramics were synthesized by the solid-state reaction method. The upconversion emission properties of Er3+ doped KNN ceramics were investigated as a function of Er3+ concentration and incident pumping power intensity. Bright green (~555 nm) and red (670 nm) upconversion emission bands were obtained under 980 nm excitation at room temperature, which are attributed to (2H11/2, 4S3/2)→4I15/2 and 4F9/2→4I15/2 transitions, respectively. The upconversion emission intensity can be adjusted by changing Er3+ concentration, and the mechanism of upconversion processes involve not only a two-photon absorption but also a three-photon absorption. In addition to the admirable intrinsic piezoelectric properties of KNN, this kind of material may have potential application as a multifunctional device by integrating its upconversion and piezoelectric property.

•Eu3+-doped BNT red phosphors were prepared by the solid-state reaction.•BNT:Eu3+ exhibits high efficient red emission (618 nm) with η=0.50.•BNT:Eu3+ materials are potential candidates for the application in W-LEDs.An efficient red-emitting phosphor, Bi0.5Na0.5TiO3:Eu3+, was synthesized by the solid-state reaction. The Bi0.5Na0.5TiO3:Eu3+ phosphor showed a strong red emission corresponding to the 5D0→7F2 (618 nm) transition of Eu3+ under blue excitation (464 nm). The emission intensity reached its maximum when Eu3+-doped concentration is 0.25 mol. Furthermore, Bi0.5Na0.5TiO3:0.25Eu3+ revealed high quantum yield (η=0.50) and smaller full width at half-maximum (FWHM) values (5 nm). These results show that Bi0.5Na0.5TiO3:Eu3+ material is a promising red phosphor for application in W-LEDs with blue LEDs chip.

Ferroelectric oxides with optical, electrical and mechanical multifunctions have great potential applications in future optoelectronic devices. We examined the Er doped BaBi4Ti4O15 (BBT) layered ferroelectric oxides and demonstrated that a certain amount of Er doped ceramic sample shows a bright up-conversion photoluminescence (UC) while simultaneously obtaining enhanced ferroelectric properties and increased Curie temperature (Tc). The UC properties of doped BBT ceramics were investigated as functions of Er3+ concentration and incident pump power. Green (557 nm) and red (670 nm) emission bands were obtained under 980 nm excitation at room temperature. Studies of dielectric constant and dielectric loss with different temperature indicated that introduction of Er increased the Tc with relatively lower values of dielectric loss of BBT thus making this ceramic suitable for sensor applications at higher temperatures. Meanwhile, Er introduction improved the ceramic’s ferroelectric properties by increasing the remnant polarization making it suitable for effective ferroelectric devices. As a multifunctional material, Er doped BBT showed a great potential to be used in sensor, optical-electrical integration and coupling devices.Highlights► Er doped BaBi4Ti4O15 layered ferroelectric oxide was synthesized for the first time. ► The doped BaBi4Ti4O15 showed a bright up-conversion photoluminescence. ► At the same time, the doped sample showed enhanced ferroelectric properties. ► Additionally, introduction of Er increased the Tc with relatively less values of dielectric loss. ► The doped sample could be used for sensor, optical-electro integration and coupling devices.

In this paper, Pr doped CaBi4Ti4O15 ceramics were prepared by a traditional solid state method. Crystal structure and morphologies of the ceramics were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The photoluminescence properties of the samples were investigated by a spectrofluorometer. Three excitation bands are located at wide range of wavelength, which are 300–430 nm, 440–510 nm and 550–570 nm respectively. Upon the excitation of 494 nm light, the samples shows an emission peak centered at 614 nm, corresponding to 1D2 → 3H4 transition. A 614 nm red emission excited under the wave with long wavelength of Pr doped CaBi4Ti4O15 makes it useful in the white LEDs. In addition, it is an intrinsic ferroelectric and piezoelectric material; the enhanced ferroelectric properties were obtained by Pr doping. As a multifunctional materials, Pr doped CaBi4Ti4O15 may be useful in white LEDs, sensor, and optical-electro integration.

Ferroelectric (1 − x)BaTiO3-x(Na0.5Ho0.5)TiO3 ceramics with ferroelectric and up-conversion luminescent multifunctions were designed and fabricated by a solid state reaction process. Their structure, ferroelectric, piezoelectric, up-conversion photoluminescence and relative optical temperature sensing properties were investigated systematically. Crystal structure analysis and Rietveld refinements based on the powder X-ray diffraction data show that the ceramics crystallized in the tetragonal perovskite space group P4mm at room temperature. Enhanced electrical properties and strong green up-conversion luminescence with thermally coupled green emission bands centered at 523 and 553 nm were observed. For a typical sample x equals 0.05, a large electrostrain of 0.279% was obtained under a 70 kV cm−1 electric field that is comparable to that of the PZT4. Meanwhile, the excellent optical temperature sensitivity (0.0063 K−1 at 480 K) is higher than that of Er-doped BaTiO3 nanocrystal materials. The results suggest that the BaTiO3-(Na0.5Ho0.5)TiO3 material should be an attractive material for piezoelectric actuator and temperature sensing device applications.