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Five new zero-dimensional hybrid manganese halides based on discrete [MnCl4]2− tetrahedrons were prepared and used as highly efficient green-light emitters. Through rational management of organic cations to tailor the Mn⋯Mn separation distances between neighboring [MnCl4]2− tetrahedrons, the photoluminescence quantum yield increased significantly from 7.98% to 81.11%.

A facile, green and economical preparation technique is critical for the cost-effective scale-up manufacture and optoelectronic device engineering of halide perovskites. Herein, we developed a viable solvent-free mechanochemical synthetic route to systematically prepare organic–inorganic hybrid perovskites. In this work, an enormous halide library comprising 16 zero-dimensional hybrid manganese halides with the formula of AnMnX4 (A = organic cations, X = Cl, Br, n =1, 2) was synthesized through an economically and environmentally friendly mechanical grinding solid-state reaction within a quite fast time of 40 s and 100% yield. Even without any crystallization process, these AnMnX4 display strong green light emissions with the highest photoluminescence quantum yield (PLQY) of 79.5%, which reaches up to the top rank of green-light-emitting halide perovskites. Moreover, the enormous structural library facilitates us to build up a direct correlation between intermolecular Mn⋯Mn distances and PLQY, which provides a feasibility of fine-tuning luminescence performance by reasonably managing organic species to tailor the Mn⋯Mn distance. This work not only paves a green assembly way of hybrid perovskite materials but also provides a generalized method to rationally optimize the luminescence performances of hybrid manganese halides, which is potentially extended to all emissive hybrid metal halides.

An ultrapure green phosphor with narrow emission range (525–535 nm) and full width at half maximum (FWHM < 25 nm) is critical for a backlit light-emitting diode to realize an ultrawide color gamut in liquid-crystal display (LCD), according to the Rec. 2020 standard. However, it is extremely formidable to achieve this goal for low-dimensional halide perovskites (LDHPs), which readily display broadband emissions arising from self-trapped excitons due to strong electron–phonon coupling. Herein, we report a new one-dimensional (1D) hybrid lead halide of [TMPDA]2Pb3Br10 (TMPDA = tetramethyl-1,3-diaminopropane) displaying unusual ultrapure green light emission. Benefiting from the synergistic work of weak electron–phonon interaction and strong quantum confinement, this 1D halide displays sharp green emission at 526 nm with narrow FWHM (25 nm), high photoluminescence quantum yield (71.95%) and color purity (91.1%), which achieves the Rec. 2020 standard and represents the purest green emitting LDHP to date. Remarkably, as a down-conversion green phosphor, [TMPDA]2Pb3Br10 provides an ultrawide color gamut covering 121.5% of NTSC and 90.7% of Rec. 2020 standards, showcasing the application in high-resolved LCD. The establishment of a fundamental structure–property relationship also paves a new way to rationally design novel narrow-band emitting LDHPs as a supplement of colloidal 3D perovskite nanostructures.

Recently, low-dimensional organic–inorganic hybrid metal halides have attracted considerable attention in solid-state optical application fields, especially in white-light emitting diodes (WLEDs) owing to intrinsic broadband luminescence performances. Herein, by selecting different types of organic cations as a structural decoration strategy, we designed a series of new 1D hybrid halides of A2Pb3Br10 (A = NPM, DMPDA, TMEN) based on same [Pb3Br10]4− chains composed of edge-shared [Pb3Br12]6− trimers. The low-dimensional crystal lattice results in the formation of self-trapped excitons, which leads to broadband light emissions covering the entire visible region for all A2Pb3Br10 homologues. Specifically, compound 1 exhibits yellowish-white light emission (0.34, 0.45) with a photoluminescence quantum efficiency of 2.51%. Both compounds 2 and 3 show bluish-white light emissions centered at 438 nm and 440 nm, respectively, with high color rendering index (CRI) of 96, which belongs to one of the highest values to date. The intrinsic broadband white light emissions enable them as promising candidates for single-component white-light emitting materials.

The Eu-doped K0.5Na0.5NbO3 pellucid ceramics were first prepared via a conventional solid-state reaction, and they exhibited light illumination-induced high-contrast photochromism of both optical transmittance and photoluminescence behaviors. Through thermal treatment, the optical performances could return to their initial states and displayed excellent reversibility. Eu3+ ions were selected as the luminescent activator for detecting the local environment of the K0.5Na0.5NbO3 host. Meanwhile, the effects of the amount of Eu3+ present on phase structures, microstructures, optical transmittance and photoluminescence intensities were systematically investigated. The results suggest that Eu-doped K0.5Na0.5NbO3 transparent ceramics possess multifunctionality including photochromism, photoluminescence and optical switching properties, and that they exhibit promising potential for non-destructive optical data storage application.

Er3+-doped Ba0.85Ca0.15Ti0.9Zr0.1O3 (xEr-BCTZ, x = 0, 0.005, 0.01, 0.015) multifunctional thick films were prepared by the tape-casting method, using sol-gel-derived nano-sized powders as the matrix material. The surface morphologies, photoluminescence, and electrical properties were investigated. Dense microstructures with pure perovskite structure were obtained in the thick films. By doping an appropriate amount of Er3−, the samples exhibit superior up-conversion photoluminescence performance and simultaneously enhanced electrical performances. In addition, relatively higher texture fractions (with the largest value of 83.5%) were realized through introducing plate-like BaTiO3 templates to make the thick film grow by the [001]c orientation. And the ferro-/piezoelectric properties of the thick films were further improved, showing potential in the applications of micro-optoelectronic devices.

A novel photochromic (PC) ferroelectric material, Nd3+-doped K0.5Na0.5NbO3 translucent ceramic, was fabricated by a conventional solid method. The ceramic shows moderate optical transparency due to its dense microstructure, as well as good photoluminescence (PL) properties of up-conversion (UC) emission in the visible region and down-shifting (DS) emission in the near-infrared region. Simultaneously, the colors of all the ceramics turn darker after 365 nm illumination, and then recover to their initial states upon thermal stimulus (210 °C, 10 min), exhibiting a typical PC phenomenon. In particular, the effect of the PC behavior on PL lifetimes of Nd3+ was investigated. Multi-mode reversible modulations of various optical behaviors were realized based on the PC behavior, especially for the regulation of near-infrared emission. And the maximum modulation ratios of transmittances, UC or DS PL intensities and luminescence lifetimes are 43.0%, 66.7%, 66.4% and 12.8%, respectively. Owing to high-temperature sintering and Nd3+ substitution in the ceramics, cation and oxygen vacancies appear to produce F′ and V1 color centers, which are in charge of the PC behavior and corresponding modulations. These results suggest that the ceramics are a promising PC material in visible and near-infrared optical data storage, photo-switches, and optoelectronic devices. Meanwhile, they also provide insights into the applications of rare-earth Nd3+ in other inorganic PC ferroelectric materials.

Er3+-doped xK0.5Na0.5NbO3-(1-x)Ba0.85Ca0.15Ti0.9Zr0.1O3 (x = 0.04, 0.05, 0.06 and 0.07) translucent ceramics have been first prepared by conventional pressureless sintering. Owing to the effective suppression of grain growth induced by both Er3+ and K0.5Na0.5NbO3, the ceramics possess dense and fine-grained microstructure. The XRD patterns demonstrate cubic-like phase structure with minimal optical anisotropy. The ceramics perform good photochormic (PC) properties under 407-nm light irradiation and superior reproducibility after heat treatment (200 °C, 5 min). And PC reaction is responsible for coloration and decoloration processes. The up-conversion photoluminescence before and after irradiation have been studied. With increasing the K0.5Na0.5NbO3 content or elevating the sintering temperature of the ceramics, the luminescent quenching degree (ΔRt) gradually increases. The color centers induced by irradiation can be reversibly created or eliminated, resulting in invertible luminescent modulations. This work can guide other multifunctional PC transparent ferroelectric materials for optoelectronic applications.

In recent years, although low-dimensional hybrid lead halides have received great attention due to the fascinating photoluminescent (PL) properties, the research is still on the early stage and only limited phases have been explored and characterized. Here, by introducing heterometals as mixed structural compositions and optical activity centers, we prepared a series of low-dimensional hybrid heterometallic halides, namely as, [(Me)-DABCO]

The lead-free 0.5(Ba0.7Ca0.3)TiO3–0.5Ba(Ti0.8Zr0.2)O3 (BCTZ) ceramics with Er doping have shown good upconversion photoluminescence (PL) and desirable optical temperature sensing properties. To bridge a relationship between the structure/intrinsic defects and properties of rare-earth-doped ferroelectrics, we designed and fabricated a series of BCTZ ceramics doped with 1 mol % Er3+ by combining the first-principles calculations and experimental measurements. Theoretically, we discovered that Er can occupy both A sites (i.e., replacing Ba or Ca) and B sites (i.e., replacing Ti or Zr) in the BCTZ lattice and highlighted that the Er-doping-induced vacancy concentration decreases for both the oxygen vacancies (Vo) and cation vacancies (Vc). Experimentally, the enhanced PL performance and the dielectric, ferroelectric, and piezoelectric properties of the Er-doped BCTZ ceramics have been observed. Finally, the physical origin of Er-induced property enhancement in BCTZ has been elaborated according to the charge ...

Er-doped K0.5Na0.5NbO3-SrTiO3 transparent ceramics were fabricated by traditional pressureless sintering. The dual effects of Er3+ and SrTiO3 contents on the microstructures, optical transparencies and optoelectronic properties of the ceramics were investigated. The introduction of Er3+ and Sr2+ results in decreasing grain size and generating cation vacancies, affecting the density and uniformity of the ceramics. The ceramics exhibit superior transmittance: T ∼55% in the visible region (760 nm) and ∼75% in the infrared region (2000 nm), which is dependent on optical band gap energy. In terms of electrical properties, the ceramics also possess relaxor-like characteristics, low dielectric loss and suitable piezoelectric constants. Due to Er3+, the ceramics exhibit composition-tunable green and red up-conversion photoluminescence emissions, whose intensities are related to the crystal symmetry. Combined with good optical and electrical properties, the ceramics open up potential applications in the electrical/optical interdisciplinary field, such as visible displays, solid-state lasers and transparent electronic devices.

By simply doping with a certain amount of Sm3+, opaque lead-free (K0.5Na0.5)NbO3 piezoelectric ceramics were fabricated into transparent/translucent ceramics. The photochromic (PC) behavior and associated reversible transmittance/luminescence modulation were realized via physical means. Upon illumination under a xenon lamp, the maximal decreased values of optical transmittance and luminescence intensity are 36.1% and 49%, respectively. Meanwhile, the colors of all the ceramics turn darker after illumination, and subsequently return to their initial states by thermal stimulus (200 °C for 5 minutes), exhibiting a typical PC phenomenon. Combining experimental and calculation results, it can be found that the PC mechanism is closely related to the vacancy defects induced by both high-temperature sintering and Sm3+-doping. Additionally, the Sm3+ effects on phase structures, microstructures, optical transmittance and photoluminescence properties of the ceramics were systematically studied. The substitution behavior of Sm3+ and vacancy defect concentrations on the energy band gap of the material were unraveled by the first principles calculations to further clarify the corresponding mechanism. The Sm3+-doped (K0.5Na0.5)NbO3 transparent ceramics have potential for application in modulation and conversion of photoenergy, such as in optical memory and photo-switching devices. And the reversible tuning of transmittance in our material is especially attractive for exploring novel transparent PC materials.

Herein, the tape-casting technique was used to fabricate an Er-doped (K0.5Na0.5)NbO3 (KNN:0.02Er) laminar ceramic, which possesses a pseudo-cubic phase structure with regular cube-shaped grains. Considering the substitution behavior of the Er dopant in the KNN lattice, X-ray diffraction analysis and density functional theory simulations both verify that Er can replace K and Na sites. And Er-induced enlargement of the energy band gap of KNN:0.02Er has been obtained in the reflectance spectra and simulations. Furthermore, the ceramic exhibits dual-mode down-conversion and up-conversion photoluminescence (PL). As a lead-free luminescent ferroelectric, the PL intensity of KNN:0.02Er can be enhanced by polarization induced by electric poling. And the dual-mode PL can be obviously modulated under an electric field in an in situ, reversible, real-time and dynamical way. Our results offer an effective theoretical way to bridge the relationship between the crystal structure/chemical bonding environment and the performance of the KNN system, and also provide an opportunity to realize electrically controlled tuning of the PL response in KNN-based luminescent ferroelectrics and the corresponding optoelectronic devices.

Recently, organic–inorganic hybrid lead halides have been explored as photoluminescent (PL) materials with flexible structural tunabilities and high photoluminescence quantum efficiencies, which can be modified by the structure regulating functions of organic cations. Here, by adopting different saturated organic cations as structure directing agents (SDAs), a series of organic–inorganic hybrid lead halides have been solvothermally synthesized and characterized with different structural types. Compound [(CH3)2NH2]2[H2DABCO]2Pb3I12 (1, DABCO = 1,4-diazabicyclo[2.2.2]-octane) features a linear zero-dimensional (0D) [Pb3I12]6− trimer, and [(Me)6-en]2Pb3I10 (2) and [H2N-Prpipz]2Pb3Br10 (3) contain two different types of one-dimensional (1D) [Pb3X10]4− chains based on the C3-symterric [Pb3X11] trimer and [PbX6] unit, respectively. In the structures of H[(Me)2-DABCO]Pb3I9 (4) and H[(Me)4-pipz]Pb3I9 (5, pipz = piperazine), the C3-symmetric [Pb3I11] trimers are interlinked to form the same two-dimensional (2D) corrugated [Pb3I9]3− layers. Under the excitation of UV irradiation, these hybrid lead halides exhibit tunable luminescence properties from yellow, orange to red emissions with the largest Stokes shift of 335 nm. The PL nature is also investigated based on temperature-dependent PL emission, time-resolved PL and theoretical calculations, etc. These hybrid lead halides provide new types of structural models to probe into the PL properties and understand the underlying structure–property relationship.

In recent years, low-dimensional lead halides have emerged as some of most attractive photoelectric materials due to their intrinsic broadband emissions with a potential application in white-light emitting diodes. To achieve the desired performance, tremendous research has emphasized the modulation of inorganic components as optical centers; however, less work has paid attention to the direct contribution of the organic components. Herein, we successfully assembled two new hybrid lead halides of [H2BPP]Pb2X6 (X = Br, 1, and Cl, 2) containing one-dimensional double [Pb2X6]2- chains using optically active 1,3-bis(4-pyridyl)-propane (BPP) as an organic cation. Under UV-light excitation, compounds 1 and 2 exhibit broadband yellowish-green emissions, which were verified by promising photoluminescence quantum efficiencies (PLQEs) of 8.10% and 4.84%, respectively. The broadband light emissions are derived from the combination of dual higher-energy blue and lower-energy yellow light spectra, which can be attributed to the individual contributions of the organic and inorganic components, respectively, according to the time-resolved and temperature-dependent emission spectra as well as theoretical calculations. This work proves the great contribution of organic components to the photophysical properties and provides a new design strategy to realize broadband light emission by rationally combining the dual-emitting properties of different assembly blocks.

Considering the instability and low photoluminescence quantum yield (PLQY) of blue-emitting perovskites, it is still challenging and attractive to construct single crystalline hybrid lead halides with highly stable and efficient blue light emission. Herein, by rationally introducing d10 transition metal into single lead halide as new structural building unit and optical emitting center, we prepared a bimetallic halide of [(NH4 )2 ]CuPbBr5 with new type of three-dimensional (3D) anionic framework. [(NH4 )2 ]CuPbBr5 exhibits strong band-edge blue emission (441 nm) with a high PLQY of 32 % upon excitation with UV light. Detailed photophysical studies indicate [(NH4 )2 ]CuPbBr5 also displays broadband red light emissions derived from self-trapped states. Furthermore, the 3D framework features high structural and optical stabilities at extreme environments during at least three years. To our best knowledge, this work represents the first 3D non-perovskite bimetallic halide with highly efficient and stable blue light emission.

Recently, 2D organic-inorganic hybrid lead halide perovskites have attracted intensive attention in solid-state luminescence fields such as single-component white-light emitters, and rational optimization of the photoluminescence (PL) performance through accurate structural-design strategies is still significant. Herein, by carefully choosing homologous aliphatic amines as templates, isotypical perovskites [DMEDA]PbCl4 (1, DMEDA=N,N-dimethylethylenediamine) and [DMPDA]PbCl4 (2, DMPDA=N,N-dimethyl-1,3-diaminopropane) having tunable and stable broadband bluish white emission properties were rationally designed. The subtle regulation of organic cations leads to a higher degree of distortion of the 2D [PbCl4 ]2- layers and enhanced photoluminescence quantum efficiencies (

The BaZrx Si3 O7+2x :Eu2+ /Eu3+ (2%, molar ratio) phosphors were prepared with adding different amounts of zirconium dioxide (ZrO2 ) (x = 0, 0.2, 0.4, 0.6, 0.8, and 1) by a self-reduction method under air conditions. X-ray diffraction, photoluminescence properties, thermal quenching properties and luminescent lifetimes of the prepared samples were systematically analyzed. In BaZrx Si3 O7+2x :Eu2+ /Eu3+ , both the 4f → 5d transitions of Eu2+ and sharp emissions assigned to 5 D0 → 7 FJ (J = 0, 1, 2, 3, 4) transitions of Eu3+ were observed. In addition, the results also reveal that the amount of ZrO2 affects the crystal structure, the self-reduction process and further influences the relative intensity of Eu2+ /Eu3+ in all samples. Therefore, the diverse emission colors can be obtained and modulated by controlling the content of ZrO2 . The highlight of this work is that the white light emission is observed, when x is 0.4, 0.6, 0.8 and 1, respectively.

The development of new visible light-driven photocatalysts based on semiconducting materials remains a greatly interesting and challenging task for the purpose of solving the energy crisis and environmental issues. By using photosensitive [(Me)2-2,2′-bipy]2+ (1,1′-dimethyl-2,2′-bipyridinium) cation as template, we synthesized one new type of inorganic−organic hybrid cuprous and silver halogenides of [(Me)2-2,2′-bipy]M8X10 (M = Cu, Ag, X = Br, I). The compounds feature a three-dimensional anionic [M8X10]2– network composed of a one-dimensional [M8X12] chain based on MX4 tetrahedral units. The photosensitization of organic cationic templates results in narrow band gaps of hybrid compounds (1.66–2.06 eV), which feature stable visible light-driven photodegradation activities for organic pollutants. A detailed study of the photocatalytic mechanism, including the photoelectric response, photoluminescence spectra, and theoretical calculations, shows that the organic cationic template effectively inhibits the rec...

The lead-free 0.985(K0.5Na0.5)NbO3-0.015ErBiO3 (KNN-EB-0.015) ceramic was fabricated by pressureless sintering. It possessed a pure perovskite phase with pseudo-cubic symmetry. Due to the fine-grains, small-sized pores, dense microstructure and relaxor-like characteristics, the ceramic was optically clear, exhibiting the highest transmittances of ∼40% and ∼71% in the visible and infrared regions, respectively. The photoluminescence (PL) properties of the ceramic were studied, including the up-conversion (UC) green and red emissions, down-conversion near infrared emission as well as the emission lifetimes. The color-tunable (from green to yellow) UC emissions were observed by increasing the temperature, based on the temperature-dependent emission spectra, which also exhibited good thermal stability (52.6% of the initial intensity at 453 K) of the ceramic. Additionally, the temperature sensing properties were investigated using the fluorescence intensity ratio technique. A maximum sensitivity of ∼0.0048 K at 603 K was obtained. Combined with the good optical and electrical properties, the KNN-EB-0.015 transparent ceramic could be a promising candidate for multifunctional optoelectronic applications.

Er-doped (K 0.5 Na 0.5 ) 1− x Li x Nb 1− x Bi x O 3 (0.05 ≤ x ≤ 0.08) ceramics have been prepared by pressureless sintering. Because of the cubic-like phase as well as the dense and fine-grained structure, the ceramics are optically clear, exhibiting high transmittances in the near-infrared and mid-infrared (MIR) regions (∼50% and ∼75%, respectively). They also possess strong electro-optic (EO) response, giving a large effective linear EO coefficient (128–184 pm/V). Owing to Er 3+ , the ceramics exhibit green and red up-conversion photoluminescence (PL) emissions, which are sensitive to the crystal symmetry of the ceramic host. The ceramics also exhibit a low absorption coefficient of OH − groups and then distinct and broadband MIR emissions. Together with the relatively large piezoelectric coefficient (70–90 pC/N), high dielectric constant (∼1400) and low dielectric loss (∼0.03), the ceramics open up potential applications in electrical/optical interdisciplinary field, such as visible displays, MIR solid lasers and optical attenuators.

In recent years, organic-inorganic hybrid metal halides have emerged as a highly promising class of semiconducting light emitting diodes (LEDs) due to their fascinating photoluminescence properties. Here, by specifically selecting different organic cations as templates, a series of new hybrid cuprous halides have been solvothermally prepared, namely [Me-Py]CuI2 (1), [(Me)2-DABCO]Cu2I4 (2), [Me-MePy]Cu2I3 (3), and [H2DABCO]Cu3X5 (X = I (4) and Br (5)). These hybrid cuprous halides feature one-dimensional (1D) [CuI2]-, [Cu2I3]- and [Cu3X5]2- (X = Br, I) chains surrounded and charge-balanced by organic cations. Under UV photoexcitation, these hybrid cuprous halides exhibit strong tunable photoluminescence from cyan (480 nm) to red (675 nm) emissions with large Stokes shifts (345 nm). The intrinsic nature of PL emissions is also investigated based on temperature-dependent PL emission, lifetime, photoluminescence quantum efficiencies, etc.

Cr3+-Yb3+ codoped bulk glass-ceramics containing KZnF3 nanocrystals are fabricated by thermal treatment of cast glass samples and characterized by X-ray diffraction and transmission electron microscopy. The luminescent properties of the glass and glass ceramic are investigated from the measured photoluminescence spectra and fluorescent lifetime. The measurement results demonstrate that Cr3+ and Yb3+ ions are both predominantly hosted in the KZnF3 nanocrystals, and the energy absorbed by Cr3+ ions is efficiently transferred to Yb3+ ions when excited at 450 nm. Compared to the glass, the near-infrared emission in the Cr3+-Yb3+ codoped glass ceramics is significantly enhanced when the excitation wavelength lies in the range λ~400–800 nm of a solar simulator. Results indicate that the Cr3+-Yb3+ codoped KZnF3 glass ceramic provides a promising material for spectral conversion from visible sunlight to near-infrared emission and a novel gain material for solar pumped fiber laser.

Er3+-doped Ba0.85Ca0.15Ti0.9Zr0.1O3 (xEr-BCTZ, x = 0, 0.005, 0.01) ferroelectric-luminescent thin films were prepared by the chemical solution deposition method. The effects of annealing temperature on microstructures of the samples were examined. Fine, uniform and well-crystallized thin films with pure perovskite structure were obtained through annealing at 750 °C. And the number of pores reduce with denser microstructure by increasing the Er3+ content. Additionally, ferroelectric and photoluminescence (PL) properties of xEr-BCTZ thin films were studied. Owing to dense microstructure and few defects, high remanent polarization and strongest up-conversion PL intensity were obtained at x = 0.01. The result of X-ray photoelectron spectroscopy confirms the existence of oxygen-related defects in the films, which can partly deteriorate the ferroelectricity and PL intensity. This work can guide other multifunctional lead-free ferroelectric-luminescent thin films for micro-optoelectronic applications.

Pr 3+ /Er 3+ -doped 0.93Bi 0.5 Na 0.5 TiO 3 –0.07BaTiO 3 ceramics have been fabricated at a low sintering temperature of 960°C using a sintering aid of Li 2 CO 3 . The effects of energy transfer between Pr 3+ and Er 3+ on their photoluminescence properties have been investigated. Our results reveal that the down-conversion emissions of Pr 3+ are weakened and the lifetimes are shortened by the co-doping of Er 3+ . As a result, when both Pr 3+ and Er 3+ are excited simultaneously, with increasing the concentration of Er 3+ , the green emissions from Er 3+ increase but the red emissions from Pr 3+ decrease. Moreover, the emission color of the ceramics can be reversibly changed between red, yellow and yellowish green by using excitation sources of different wavelengths. Strong up-conversion green emissions with short lifetimes arisen from Er 3+ have also been observed for the ceramics under the excitation of 980 nm. Owing to the Li 2 CO 3 sintering aid, the low-temperature sintered ceramics also exhibit reasonably good ferroelectric and piezoelectric properties, and hence should be promising for multifunctional applications such as electro-optical coupling devices.

Ultraviolet light is a necessary light source for humans. As typical ultraviolet emission materials, Pb2+ doped phosphors have been widely investigated. Here, we report a Pb2+ activated silicate material. Under the excitation of 258 nm ultraviolet light, Sr2MgSi2O7:Pb2+ can emit broadband ultraviolet light with a peak at 333 nm. The luminescence intensity can be adjusted by changing the Pb2+ doping concentration, and the experiments show that the optimum concentration is 0.02. The critical distance for the corresponding concentration quenching was calculated to be 19.92 A. By gradually decreasing the Sr/Ba ratio, the luminescence wavelength is gradually shifted from 333 to 383 nm due to the increase of Pb2+-O2−covalency. The continuous replacement of Sr by Ba atoms does not change the crystal structure, and the emission wavelength adjustable range is 50 nm. Our research adds new members to the Pb2+-activated phosphor family. At the same time, the successful use of atomic substitution method provides a reference for the adjustment of the emission wavelength of Pb2+ doped materials.

In this research, a series of La1-xB3O6: xDy3+ phosphors were synthesized for white light-emitting diode applications using the high-temperature solid-state method. The LaB3O6 structure and XRD of prepared samples were analyzed. Under 350 nm excitation, La1-xB3O6: xDy3+ phosphors can emit white light consist of blue (4F9/2→6H15/2) and yellow (4F9/2→6H13/2) light. The optimal doping concentration of Dy3+ is 0.02. The typical sample La0.98B3O6: 0.02Dy3+ with excellent thermal stability (integral emission intensity maintained at 51% of that at room temperature) was confirmed, and the activation energy was calculated to be 0.203 eV. The CIE coordinates of La0.98B3O6: 0.02Dy3+ is calculated as (0.313, 0.339), which is close to ideal white light. The research results indicate that La1-xB3O6: xDy3+ phosphors are promising candidate w-LEDs excited by ultraviolet light.

0.93(Bi 0.5− x /0.93 Er x /0.93 Na 0.5 )TiO 3 –0.07BaTiO 3 photoluminescent ceramics have been prepared by a conventional ceramic fabrication technique and their photoluminescence, ferroelectric, dielectric and piezoelectric properties have been studied. Under an excitation of 980 nm, the ceramics exhibit visible up-conversion luminescent emissions at 532 nm (green), 540 nm (green) and 600 nm (red), as well as broadband down-conversion luminescent emissions in near-infrared (1.44–1.66 μm) and mid-infrared (2.62–2.84 μm) regions. The quenching concentration for the ceramics is high, about 6%, and both the visible and invisible emissions are very strong. Among the emissions, the photoluminescence intensity of the red emission band increases most significantly by more than 47 times as the Er-concentration increases from 0.005 to 0.07. As a result, the Commission Internationale de L’Eclairage chromaticity coordinates shift from (0.29, 0.69) to (0.49, 0.50), and the emission color changes from green to yellowish green. Owing to the establishment of a dynamic circulatory energy process at high Er-concentrations, the photoluminescence intensity of the mid-infrared emission increases significantly by more than 4 times at the expense of the near-infrared emission. Together with the good ferroelectric and piezoelectric properties, the ceramics should be promising candidates for multifunctional optoelectronic applications.

Er/Pr-doped K0.5Na0.5NbO3 ceramics have been fabricated and the effects of Pr3+ on their photoluminescence properties have been investigated systematically. The visible upconversion emissions, near-infrared and mid-infrared downconversion emissions of Er3+ ions under the excitation of 980 nm have been studied in detail. The effects of Pr3+ on PL properties and energy-transfer processes have also been elucidated. By selecting an appropriate excitation source, simultaneous visible downconversion emissions of Er3+ and Pr3+ ions can be realized, and the emission colors of the ceramics can be tuned via the concentration of Pr3+ ions in a wide range from yellowish green to yellow. Our results also reveal that the photoluminescence emissions of the ceramics can be enhanced by the alignment of polarization of the ferroelectric host.

The lead-free ceramics K0.5Na0.5NbO3 doped with x mol% Er3+ ions have been successfully manufactured and their photoluminescence properties, including the up-conversion visible (480–700 nm) emissions, down-conversion near infrared (1400–1680 nm) and middle infrared (2620–2850 nm) emissions, emission colors and lifetimes of the energy levels have been systemically investigated. The corresponding photoluminescence mechanism has been discussed in detail. Our results show that the Er-doping induces a phase transition from orthorhombic to cubic-like as well as inhibits the grain growth due to the donor-type nature. Both the change of crystallographic structures and concentration-quenching effect induced by Er3+ ions have great influences on the photoluminescence properties. Because of the wide emission ranges and long lifetimes, Er-doped K0.5Na0.5NbO3 ceramics are the promising candidates for optoelectronic applications.

Ferroelectric oxides with luminescent ions hold great promise in future optoelectronic devices because of their unique photoluminescence and inherent ferroelectric properties. Intriguingly, the photoluminescence performance of ferroelectric ceramics could be modulated by an external electric field. However, researchers face a current challenge of the diminutive extent and degree of reversibility of the field-driven modification that hinder their use in room-temperature practical applications. Within the scope of current contribution in rare-earth-doped bismuth sodium titanate relaxors, the most important information to be noted is the shifting of the depolarization temperature toward room temperature and the resulting considerable enhancement in ergodicity, as evidenced by the dielectric properties, polarization, and strain hysteresis, as well as the in situ Raman/X-ray diffraction studies. After the introduction of 1 mol % Eu, the induced composition and charge disorders disrupt the original long-range ferroelectric macrodomains into randomly dynamic and weakly correlated polar nanoregions, which facilitates a reversible transformation between polar nanoregions and unstable ferroelectric state under an electric field, engendering a large strain. By virtue of this, both the extent and degree of reversibility of photoluminescence modulation are enhanced (∼60%) considerably, and room-temperature in situ tunable photoluminescence response is then achieved under electric field. These should be helpful for the realization of regulating the physical couplings (photoluminescent-ferroelectrics) in multifunctional inorganic ferroelectrics with a high ergodic state by reversibly tuning the structural symmetry.

Photochromic (PC) luminescent ferroelectric materials have aroused great interest because of their potential applications in optical information memories, optical switches and bio-imaging. However, those materials are basically opaque. In this work, we prepared a PC luminescent [Formula: see text][Formula: see text]NbO3-based ferroelectric transparent ceramic by modifying with [Formula: see text], [Formula: see text], [Formula: see text] and [Formula: see text], which not only have good optical transmittances ([Formula: see text]60% at 900[Formula: see text]nm), moderate ferroelectric properties and down-conversion photoluminescence (PL) properties, but also exhibit reversible PC behavior. After the illumination by xenon lamp, the colors of the ceramics change from pale green to gray, and then reversibly recover to their initial state via thermal stimulus (200∘C for 10[Formula: see text]min). Interestingly, both the optical transmittances and PL intensities can be effectively tailored by controlling the PC reaction process. The results suggest that the ferroelectric transparent ceramics are promising for the modulation of photoenergy and the design of optoelectronic devices.

Luminescent materials with dynamic photoluminescence activity have aroused special interest because of their potential widespread applications. One proposed approach of directly and reversibly modulating the photoluminescence emissions is by means of introducing an external electric field in an in-situ and real-time way, which has only been focused on thin films. In this work, we demonstrate that real-time electric field-induced photoluminescence modulation can be realized in a bulk Ba0.85Ca0.15Ti0.90Zr0.10O3 ferroelectric ceramic doped with 0.2 mol% Pr3+, owing to its remarkable polarization reversal and phase evolution near the morphotropic phase boundary. Along with in-situ X-ray diffraction analysis, our results reveal that an applied electric field induces not only typical polarization switching and minor crystal deformation, but also tetragonal-to-rhombohedral phase transformation of the ceramic. The electric field-induced phase transformation is irreversible and engenders dominant effect on photoluminescence emissions as a result of an increase in structural symmetry. After it is completed in a few cycles of electric field, the photoluminescence emissions become governed mainly by the polarization switching and thus vary reversibly with the modulating electric field. Our results open a promising avenue towards the realization of bulk ceramic-based tunable photoluminescence activity with high repeatability, flexible controllability and environmental-friendly chemical process.

Eu2+-doped LiCaPO4 was synthesized by the high-temperature solid-state reaction. The photoluminescence excitation and emission spectra were investigated. The results show that LiCaPO4:Eu2+ phosphor can be efficiently excited by the incident lights of 280–420 nm, which well match with the emissions of near-UV light-emitting diode (LEDs). The phosphor shows a bright blue luminescence. The temperature and concentration dependence of luminescence intensities were investigated. The phosphor has an excellent thermal stability on temperature quenching effects. The luminescence decay and the color coordinates were discussed in order to further investigate its potential applications for white LED phosphors pumped by near-UV chips.

Hexagonal ZnS nanostructured spheres self-assembled from ZnS nanocrystals had been synthesized at a low temperature of 100 °C by using l -cysteine (an ordinary amino acid) as a sulfur source and gelatin (an ordinary amino acid) as the assembling agent. The reaction time, l -cysteine and gelatin all played key roles in the formation of ZnS spheres. By combining the results of X-ray diffraction (XRD), transmission electron microscope (TEM), field-emission scanning electron microscopy (FESEM), ultraviolet–visible (UV–vis) absorption and photoluminescence (PL) spectra, a structural and morphological characterization of the products was performed. The photocatalytic activity of ZnS spheres had been tested by degradation of Rhodamine-B (RB) under UV light compared to commercial Degussa P-25 TiO2 and that of ZnS prepared without gelatin or with other sulfur source, indicating that ZnS spheres synthesized by using l -cysteine and gelatin exhibit enhanced photocatalytic activity for degradation of RB.

A vanadate, Ca9Dy(VO4)7, was synthesized by the general high temperature solid-state reaction in air atmosphere. X-ray powder diffraction analysis confirmed the formation of single phase Ca9Dy(VO4)7. Photoluminescence excitation spectrum showed that the phosphor could be efficiently excited by UV–visible light from 250 to 500 nm. The characteristic emission peaks of Dy3+ were observed in the emission spectra due to the transitions of 4F9/2 → 6H15/2 at 483 nm and 4F9/2 → 6H13/2 at 573 nm. The photoluminescence measurements showed that the Ca9Dy(VO4)7 exhibited an improved chromaticity compared with YVO4:Dy3+. This was ascribed to lower site symmetry and disordered cation sites in Ca9Dy(VO4)7. The luminescence characteristics of Ca9Dy(VO4) indicated that this phosphor has a possible application for white-light-emitting diode. Luminescence mechanism and site occupancies of Dy3+ ions in Ca9Dy(VO4)7 lattices were discussed.

Pure hexagonal ZnO nanorods were synthesized by low-temperature (90 °C) solvothermal treatment of zinc acetate in 40–80 wt.% hydrazine hydrate aqueous solutions. The products were characterized by means of powder X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electronic microscopy (TEM), selected area electron diffraction (SAED), and room temperature photoluminescence (RTPL) spectra. They show a strong UV emission at around 380 nm upon excitation at 360 nm using a Xe lamp at room temperature. The influence on the quality of the nanorods was investigated while the content of the solvent changed. The as-synthesized ZnO nanorods are promising materials for nanoscale optoelectronic devices due to their excellent UV emission properties.