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A series of single phased phosphors Sr8MgLa(PO4)7: Eu2+, Mn2+, Tb3+ were synthesized by solid state reaction methods for applications of white light emitting diodes(w-LEDs). The broad absorption band at the near ultraviolet (NUV) region of 250–450 nm was obtained, which is ascribed to the 4f7→ 4f65d1 electronic transition of the Eu2+ ions. Under NUV excitation, the broad yellow emission was obtained from tri-activated Sr8MgLa(PO4)7 phosphors via combining three emission bands centered at 500, 550, and 600 nm contributed by Eu2+, Tb3+ and Mn2+, respectively. The optimized concentrations of Mn2+ and Tb3+ were 6 mol%, respectively, which enhanced the total PL intensity up to 30% comparing to only Eu2+ doped phosphor. Moreover, the quantum efficiency of Sr8MgLa(PO4)7: Eu2+, Mn2+, Tb3+ phosphor had achieved up to 52%. The combination of a NUV chip with compound of Sr8MgLa(PO4)7: Eu2+, Mn2+, Tb3+ and BaMgAl10O17:Eu2+ achieved tunable w-LEDs with high CRI. The results suggest that this single phased Sr8MgLa(PO4)7: Eu2+, Mn2+, Tb3+ phosphor can be a key for the phosphor converted w-LEDs for warm white light emission.

A series of the Eu3+-activated Gd2W1-xMoxO6 phosphors were synthesized by a high-temperature solid-state reaction method. The phase composition, ultraviolet-visible diffuse reflectance spectra, photoluminescence and decay properties of the phosphors were investigated. Through adjusting the Mo6+ ion concentration, the excitation band of the studied sample was gradually shifted to longer wavelength. Under 376 nm excitation, the strong red emission at 610 nm and weak yellow emission centered at 591 nm were detected, indicating that Eu3+ occupies non-inversion symmetry sites in the host lattices. With elevating the dopant concentration, the emission intensity of synthesized products was greatly enhanced and achieved its optimum value when x = 0.95 which was 2.33 times higher than that of the Gd2WO6:Eu3+ compounds. The quantum efficiency of resultant samples was as high as 76.1%. Moreover, the Judd-Oflet theory was used to study the local structure environment behaviors of the Eu3+ ions in the host lattices. Finally, a red LED device, which consisted of a near-ultraviolet chip and prepared Gd2W0.05Mo0.95O6:Eu3+ phosphors, was successfully fabricated. These results confirmed that the Eu3+-doped Gd2W1-xMoxO6 phosphors have potential value as the red component for WLEDs.

Aligned Nano rods of transparent conducting indium tin oxide (ITO) were deposited on glass substrates using dc magnetron sputtering technique from an ITO alloy target at two different oxygen pressures placing the substrates at three different lateral positions inside the chamber. The (4 4 0) oriented ITO thin films at optimal deposition conditions with high transmittance, low sheet resistance, good crystallinity and novel morphology was obtained at room temperature deposition. The structural, optical, morphological, electrical transport behavior and figure of merit imply the need in optimizing the positioning of the substrates within the chamber during deposition for achieving films of best desired properties.

Nowadays, in view of health and safety demands, the controlled design of selective and sensitive sensors for Cu2+ detection is of considerable importance. Therefore, we construct herein core-shell colloidal GdVO4:Eu3+@SiO2 nanocrystals (NCs) as optical sensor for the detection of Cu2+, which were synthesized by a facile hydrothermal reaction and encapsulated with a uniform layer of ultrathin silica through a sol-gel strategy. The NCs present strong red emission due to energy transfer from VO43− groups to Eu3+ when exciting with ultraviolet (UV) light. This intense red emission from Eu3+ could be selectively quenched in the presence of Cu2+ in comparison to other metal ions and the limit of detection is as low as 80 nM in aqueous solution. It is revealed that the spectral overlap between the emission band of NCs and the absorption of Cu2+ accounts for this intriguing luminescence behavior. The detection ability is highly reversible by the addition of ethylenediaminetetraacetic acid (EDTA) with the recovery of almost 100% of the original luminescence. The luminescence quenching and recovery processes can be performed repeatedly with good sensing ability. These remarkable performances allow the colloidal GdVO4:Eu3+@SiO2 NCs a promising fluorescence chemosensor for detecting Cu2+ ions in aqueous solution.

We report a new Mg 2+ , Mn 4+ co-doped red-emitting SrLaMgTaO 6 phosphor for solid state lighting. The phosphor can be efficiently excited in the wavelength range of 250–500 nm, which matches well with the emission wavelengths of blue or NUV chips. The photo-luminescence spectra exhibit the highest emission peak at 692 nm from 2 E g → 4 A 2 spin forbidden transition of Mn 4+ under NUV excitation. The Mg 2+ co-dopant for charge compensation plays a key role in enhancing the luminescence intensity by a factor of 2.8. The incorporation of Mg 2+ ion in the host could not only suppress the energy migration among Mn 4+ ions but also eliminates the charge imbalance in Mn 4+ − Mg 2+ pairs. W-LED fabrication with different mass ratios of yellow emitting YAG: Ce 3+ and red emitting SrLaMgTaO 6 :Mn 4+ /Mg 2+ phosphors is designed to explore its possible application in warm w-LEDs with high CRI. The w-LEDs fabricated with the integration of SrLaMgTaO 6 :Mn 4+ /Mg 2+ red phosphor show changing trends toward warm white light with lower color temperature and higher CRI than that based on single yellow emitting YAG:Ce 3+ phosphors. The results suggest that SrLaMgTaO 6 : Mn 4+ /Mg 2+ phosphor has great potential for the warm w-LEDs application as a suitable red light component.

Mn 4+ -doped MGe 4 O 9 (M = Li 2 , LiNa and K 2 ) red-emitting phosphors were successfully prepared and characterized. Owing to the different ionic radii and electron configurations among the Li, Na and K ions, the MGe 4 O 9 (M = Li 2 , LiNa and K 2 ) compounds have different space group and crystal structure, such as different bond lengths, bond angles, crystal fields and nephelauxetic effect. Under the excitation of ultraviolet and blue light, the studied samples emit visible red emissions. The thermal stabilities of phosphors are greatly affected by the alkaline ions, especially when M = LiNa and K 2 , the thermal stability is significantly enhanced. Furthermore, the crystal field strength (D q ) and Racah parameters ( B and C ) are estimated to evaluate the nephelauxetic effect of Mn 4+ ions in MGe 4 O 9 (M = Li 2 , LiNa and K 2 ) host lattices. The results indicate that the alkaline ions can influence the red emissions of Mn 4+ ions in MGe 4 O 9 (M = Li 2 , LiNa and K 2 ) phosphors and these resultant phosphors may have potential applications for solid state lighting.

We report the band gap tunability of (1 − x)Na0.5Bi0.5TiO3–xBiMnO3 (x = 0.00, 0.05, 0.10 and 0.15) ceramics by a solid-state reaction method. X-ray diffraction (XRD) analysis confirmed the phase formation of rhombohedral structure with the space group of R3c. Rietveld refinement of XRD data revealed that the structural symmetry as a function of x composition. Raman analysis exhibited the vibrational phonon frequencies associated with Bi–O, Na–O, and TiO6 octahedral vibrations. The realized band gap energy variations (3.35–2.53 eV) suggesting that the synthesized ceramics materials are promising for photovoltaic and photocatalytic applications.

A soft chemical co-precipitation method has been proposed for the synthesis of YMnO3 (YMO) and Dy-modified YMO (YDMO) powders. X-ray diffraction (XRD) pattern confirms the existence of single phase in YMO and YDMO powders with hexagonal structure belonging to P63 cm space group. The crystallite sizes deduced from XRD line width analysis is found to be within 38–28 nm. A broadening and shifting of Raman-active phonon modes towards lower frequencies have been observed in YDMO in comparison to YMO. Dielectric measurements showed a gradual increase of dielectric constant values with increasing of Dy concentration. From the temperature dependent dielectric measurements, both YMO and YDMO samples showed a dielectric anomaly around 340 °C signifies the relaxation of doubly ionized oxygen vacancies. Magnetization versus magnetic field (M–H) curves of YMO and YDMO measured at room temperature suggests a paramagnetic behaviour. Compared to YMO, leakage current densities in YDMO samples are found to be improved by an order and more.

A series of color–tunable SrLa 0.93-y MgTaO 6 :0.07Dy 3+ , yEu 3+ phosphors were synthesized via solid–state reaction. The X–ray diffraction, diffuse reflectance spectra, luminescent spectra, lifetimes and thermal quenching were applied to characterize the obtained phosphors. The X–ray diffraction results revealed that the obtained phosphors possessed pure monoclinic phase. The band gap of SrLaMgTaO 6 was calculated from Vienna ab initio simulation package and diffuse reflectance spectra. The energy transfers from host to Dy 3+ and Eu 3+ ions were confirmed by the luminescence spectra. Furthermore, the SrLa 0.92 MgTaO 6 : 0.07Dy 3+ , 0.01Eu 3+ phosphor had excellent thermal stability, while the integrated PL intensity still kept about 83.34% at 150 °C of that measured at room temperature (30 °C). In addition, the warm and cold white light emission could be generated with different Eu 3+ contents. All the results of SrLa 0.93-y MgTaO 6 :0.07Dy 3+ , yEu 3+ phosphors show great potential as a single–phase white–emitting phosphor for solid state lighting applications.

Er 3+ /Tm 3+ /Yb 3+ tri-doped Sr 2 CeO 4 phosphors have been synthesized via high-energy deformation processes. The structure of the synthesized phosphor is identified to be a pure orthorhombic structure. By varying the concentration of dopant ions (Er 3+ , Tm 3+ , Yb 3+ ), the obtained phosphors present tunable up-conversion emissions under 975 nm a laser diode excitation. The white up-conversion light emitted from a 3 mol%Er 3+ /1 mol%Tm 3+ /10 mol%Yb 3+ ions tri-doped Sr 2 CeO 4 phosphor was observed corresponding to the transitions from 1 G 4 → 3 H 6 (Tm 3+ ), 1 G 4 → 3 F 4 (Tm 3+ ), 2 H 11/2 → 4 I 15/2 (Er 3+ ), 4 S 3/2 → 4 I 15/2 (Er 3+ ) and 4 F 9/2 → 4 I 15/2 (Er 3+ ) transitions at 478, 652, 526, 552 and 664 nm, respectively. The efficient up-conversion emission is attributed to energy transfer between Yb 3+ and Er 3+ or Tm 3+ ions. Moreover, there is a chance for an energy transfer from the 4 I 15/2 level of the Er 3+ to the 3 H 5 level of the Tm 3+ to enhance the blue emission. The results indicate that the synthesized phosphors can be potentially applied to many devices, such as optical displays, lighting sources for light emitting diodes and lasers.

The color-tunable emissions of Dy3+-activated SrLaMgTaO6 phosphors were synthesized via a conventional high temperature solid-state reaction method. The phase and the luminescent properties were well characterized by X-ray diffraction patterns (XRD), diffuse reflectance spectra, luminescent spectra and lifetime. The XRD result revealed the as-prepared samples exhibited a monoclinic structure with the space group P21/n. Moreover, the obtained phosphors could be efficiently excited by the UV (250 nm), near-UV (354 and 390 nm) and blue (452 nm) lights. A gradual enhancement of PL emission intensity was observed with elevating the Dy3+ ion concentration and reached its maximum value when the doping concentration was 7 mol%. The critical distance was estimated to be 15.13 A. In addition, the emission color of the as-synthesized samples were changed from blue to pure white and finally to yellow by properly adjusting the excitation wavelength and the doping concentration. All the results confirmed that Dy3+-activated SrLaMgTaO6 phosphors may have potential applications in white light-emitting diodes as white light-emitting phosphors.

By applying the sol-gel method, we fabricated Ba1−x Eu x TiO3 (BET) ceramics as a single peroveskite phase in the composition range of x = 0 ~ 0.20. The BET ceramics displayed a ferroelectric phase transition temperature that changed from 120 ◦C to 80 ◦C, and exhibited the coexistance of the tetragonal, and cubic structures as the Eu composition was increased. They also displayed anomalous dielectric behaviors related to structural relaxation in the temperature range from 200 ◦C to 600 ◦C. We considered the Arrhenius temperature dependence of the dielectric relaxation time by using the electric modulus formalism. The characteristic activation energy was thought to be related with the substitution of Eu (Eu2+, Eu3+) ions for Ba2+ or Ti4+ ions in the perovskite structure.

Substitution of Ln site in Sr9Ln(PO4)7: Eu2+ [Ln = Sc, Lu, Y, La] matrix prepared from powder-based precursors were designed for the first time. By modulating the lanthanide such as Sc, Lu, Y and La, the corresponding luminescence varied hues from yellow to blue light under 360 nm excitation. The Rietveld refinement verified the successful substitution for Ln3+ site, and the samples crystallized with the space group of I2/a for Sc, Lu, Y and R-3m for La, respectively. The internal quantum yield was found to be 24 %, 87 %, 91 %, and 100 %, respectively. The highest quantum yield phosphor of Sr9La(PO4)7: Eu2+ has potential to overcome the low efficiency of the commercial phosphors. Moreover, it possesses a high thermal quenching behavior up to 90 % emission at 423 K compared to room temperature. Therefore, a series of Sr9Ln(PO4)7: Eu2+ phosphors are expected to be exploration of technologically important material as excellent wavelength-conversion phosphor.

Eu3+-activated Ca3Mo0.2W0.8O6 phosphors, which presented bright red emissions mainly from the 5D0 → 7F2 transition of Eu3+ ions upon the near-ultraviolet and blue light excitation, were successfully prepared by a traditional high-temperature technology. The crystal structure, phase constitution, morphology, electronic structure, photoluminescent behaviors, decay time, internal quantum efficiency and thermal stability of the resultant phosphors were investigated in detail. Under the excitation of 365, 393 and 465 nm, the optimal doping concentration was 9 mol% and the electrical multipolar interaction contributed to the non-radiative energy transfer between Eu3+ ions in Ca3Mo0.2W0.8O6 host lattices. Additionally, through using the prepared compounds, commercial blue/green-emitting phosphors and light-emitting diodes (LEDs), the fabricated white-LEDs emitted warm white light with excellent performance, such as good CIE coordinates, high color rending index and low correlated color temperature, when driven by 30 mA of injection current. Ultimately, according to the response of the decay time to the temperature, the thermometric performances of the resultant phosphors in the temperature range of 298–573 K were studied. The maximum sensor sensitivity of the studied phosphors reached up to 1.16% K−1 at 523 K. These achievements revealed that Eu3+-activated Ca3Mo0.2W0.8O6 phosphors were promising candidates for solid-state lighting and thermometer.

Well-crystallized nanorod bundles Ln4O(OH)9NO3:1%Eu(Ln = Y, Lu) have been successfully prepared by hydrothermal method. The crystalline phase, size and optical properties were characterized using powder X-ray diffraction (XRD), field emission-scanning electron microscopy (FE-SEM), infrared (IR) spectrograph and photoluminescent (PL) spectra. Site occupations of Eu3+ in crystals Ln4O(OH)9NO3:Eu(Ln = Y, Lu) were discussed based on excitation spectra and the empirical relationship formula between the charge transfer (CT) energy and the environmental factor. The emission spectra exhibited that the strongest emission peaks with an excitation wavelength of 395 nm were at 617 and 626 nm in crystal Lu4O(OH)9NO3:1%Eu and Y4O(OH)9NO3:1%Eu, respectively, both of which come from 5D0-7F2 transition of the Eu3+ ions. The broad excitation peaks at about 254 and 255 nm were found when monitored at 617 and 628 nm in crystal Lu4O(OH)9NO3:1%Eu and Y4O(OH)9NO3:1%Eu, respectively, which were due to O-Eu CT transition. Based on the dielectric theory of complex crystal, the CT bands at about 254 and 255 nm in Ln4O(OH)9NO3:1%Eu(Ln = Y, Lu) were assigned to the transition of O-Eu at Ln3(Ln = Y, Lu) site, from which we can conclude that Eu3+ ions occupied the site of Ln3(Ln = Y, Lu) in crystal Ln4O(OH)9NO3:1%Eu(Ln = Y, Lu). It put forward a new route to investigate site occupation of luminescent center ions in rare earth doped complex inorganic luminescence materials.

The electric modulus relaxations were considered to be coupled phenomena between the polarization fluctuations < P 2 > due to local symmetry breaking and ionic hopping through nearest neighbor sites. The Nb-rich potassium lithium niobate (K5.595Li3.125Nb11.28O30) crystals exhibited a ferroelectric diffused phase transition around the dielectric maximum temperature T max = 350. The electric modulus relaxations were characterized by using the Cole-Davidson distribution of the electric modulus relaxation times at frequencies ranging from 100 Hz to 1 MHz. Although the lattice constants along the a-axes and the c-axes and the tetragonal unit cell volume showed linear expansions with increasing temperature T, the axial ratio c/a decreased with increasing T at temperatures below the Burn’s temperature TB. The dielectric relaxation accompanied the high ionic conduction in the temperature range above T. The ac conductivity σ'(ω) was analyzed by using the formulae, where ω O is the crossover frequency. It was considered that a double-Arrhenius behavior of the dc conductivity σ dc at temperatures around the Burn’s temperature T B was suspected of thermally activated motions in the random distribution of oxygen vacancies and lithium ions. The ac universality could result in a disordered configuration of the mobile ions, i.e., the dc conductivity at temperatures above T B . The slow relaxations of the nano-sized polar regions may contribute to the dc conductivity σ dc at temperatures below T B . The characteristic relaxation time τ CD showed a change in activation energy from 1.08 eV to 0.80 eV at temperatures around T B . The scaling factor increased in proportion to (T B − T) at T T B , but was almost constant at T >T B , where e'∞ is the high frequency dielectric constant and T is the temperature in Kelvin.

It has been still a challenge to obtain a new single-component white-light phosphor with the vanadates as host lattices and with two types of ions as activators. A systematic Ln 1 3+ /Ln 2 3+ (Ln 1 3+ /Ln 2 3+ = Dy 3+ /Tm 3+ or Dy 3+ /Sm 3+ or Dy 3+ /Eu 3+ or Tm 3+ /Eu 3+ or Tm 3+ /Sm 3+ ) coactivated Ca 9 Y(VO 4 ) 7 (CYV)samples as well as their singly doped CYV phosphors have been synthesized by the traditional solid state reaction and their photoluminescence properties have been investigated. The photoluminescence properties as a function of the concentration of rare earth ions have been discussed and the tunable luminescent color was found. The warm (CYV: 1%Dy 3+ , 1%Sm 3+ ), natural (CYV: 7% Tm 3+ ,0.5% Eu 3+ ; CYV: 1.0% Tm 3+ , 0.5% Sm 3+ ), and cold (CYV: 3% Tm 3+ ,0.5% Eu 3+ ; CYV: 0.5% Dy 3+ ,0.5% Tm 3+ ; CYV: 0.5% Dy 3+ ,0.7% Tm 3+ ; CYV: 0.3%Dy 3+ , 0.5% Tm 3+ ) white lights can be obtained. Generally, the emission intensity or lifetime of one rare earth ions decreases with increasing of the concentration of another rare earth ions.

GdVO 4 :Yb 3+ , Er 3+ powder was synthesized by a conventional solid state reaction. The XRD pattern confirmed that the GdVO 4 :Yb 3+ , Er 3+ powder phosphors have tetragonal structure. The up-conversion photoluminescence (UCPL) spectrum consisted of 2H11/2 → 4I15/2 (525 nm) and 4S3/2 → 4I15/2 (554 nm) transition. The UCPL intensity of 2H11/2 → 4I15/2 (525 nm) is stronger than 4S3/2 → 4I15/2 (554 nm) by adjusting Yb 3+ concentrations. In order to explain this behavior, we investigated a pump power dependence.

A series of orange–red emitting Y6WO12:xSm3+ (0.005≤x≤0.15) phosphors were synthesized by the convenient solid-state reaction. X-ray diffraction and photoluminescence spectra were utilized to characterize the structure and luminescence properties of the as-synthesized phosphors. The results show an efficient energy transfer from WO66− group to Sm3+ occurs. The emission spectra of the Y6WO12:Sm3+ phosphors consisted of some sharp emission peaks of Sm3+ ions centred at 571 nm, 610 nm, 675 nm, 720 nm. The strongest one is located at 610 nm due to 4G5/2–6H7/2 transition of Sm3+, generating bright orange–red light. The optimum dopant concentration of Sm3+ ions in Y6WO12:Sm3+ is around 5 mol% and the energy transfer between Sm3+ is found to be through exchange interaction. The CIE chromaticity coordinates of the Y6WO12:0.05Sm3+ phosphor were located in the orange reddish region. The Y6WO12:Sm3+ phosphors may be potentially used as orange–red phosphors for white light-emitting diodes.

An intense red-emitting NaY(MoO4)2:Eu3+ nanophosphor was developed using a hydrothermal technique. A highly pure and single-phase NaY(MoO4)2:Eu3+ nanopowder was obtained after sintering the as-prepared sample at 800 degrees C. The crystal structure and photoluminescence properties of this double molybdate were investigated. X-ray diffraction analysis showed that the NaY(MoO4)2 nanoparticles have a scheelite-type tetragonal structure, without mixed phases. Rietveld analysis provided the atomic coordinates and Mo-O-rare-earth angles. The morphology of the molybdate precursor was controlled by adjusting the synthesis conditions. The pH was found to play a crucial role in the particle size and morphology distribution. The crystalline powder phosphor exhibited intense and efficient red emissions attributed to efficient energy-transfer from MoO4(2-) to Eu3+. The chromaticity coordinates (x,y) of the NaY(MoO4)2:Eu3+ phosphor sample correspond to (0.662, 0.337). The NaY(MoO4)2:Eu3+ powder exhibited a deep-red emission under near-ultraviolet (UV) excitation, indicating a promising red phosphor for white-light-emitting diodes based on near-UV light-emitting diodes.

10 mol% Ce 3+ , 5 mol% Tb 3+ doped LaF 3 , KGdF 4 , and KYF 4 nanocrystals have been synthesized by a polyethylene glycol assisted hydrothermal method under similar synthetic conditions. The final products are characterized by X-ray diffraction patterns, field emission scanning electron microscopy images, photoluminescence (PL) excitation and emission spectra, and luminescent dynamic decay curves. The energy transfer from Ce 3+ to Tb 3+ has been observed in the final products. The Ce 3+ presents different excitation and emission properties in sensitizing Tb 3+ in the three samples. The Tb 3+ presents characteristic green emissions ( 5 D 4 → 7 F J , J =6, 5, 4, 3) and has different emission intensities in the three samples. In addition, the energy transfer from host Gd 3+ to Tb 3+ has been observed in the KGdF 4 nanocrystals. Based on the PL excitation and emission spectra and some references, energy transfer efficiency from Ce 3+ to Tb 3+ and possible energy transfer processes among Ce 3+ and/or Gd 3+ and/or Tb 3+ have been discussed.

The orange–red emitting Ba 2 CaWO 6 : x Sm 3+ (0.01≤ x ≤0.25) phosphors were synthesized via solid state reaction process. The crystal structure of the phosphor was characterized by XRD. The photoluminescence excitation and emission spectra, concentration effect were investigated. The results show an efficient energy transfer from WO 6 6− group to Sm 3+ occurs. The emission spectra of the Ba 2 CaWO 6 :Sm 3+ phosphors consisted of some sharp emission peaks of Sm 3+ ions centre at 579 nm, 618 nm, 625 nm, and 675 nm. The strongest one is located at 610 nm due to 4 G 5/2 → 6 H 7/2 transition of Sm 3+ , generating bright orange–red light. The optimum dopant concentration of Sm 3+ ions in Ba 2 CaWO 6 : x Sm 3+ is around 5 mol% and the critical transfer distance of Sm 3+ is calculated as 18 A. The fluorescence lifetime of Sm 3+ in Ba 2 CaWO 6 :0.05Sm 3+ is 2.36 ms. The Ba 2 CaWO 6 :Sm 3+ phosphors may be potentially used as orange–red phosphors for white light-emitting diodes.

A novel blue-emitting Sr5(BO3)3Cl:Ce3+,Na+ phosphor was synthesized by solid-state reaction. The excitation spectrum shows a broad band extending from 200 nm to 400 nm, and the emission spectrum shows a broad blue band peaking at 414 nm with a half width of approximately 70 nm. The optimum doping concentration of Ce3+ is found to be 0.7%. The quenching temperature for Sr5(BO3)3Cl:Ce3+,Na+ is 416 K. The calculated CIE coordinates indicate that the phosphor has good color purity. Given their broadband absorption from 250 nm to 400 nm, these phosphors meet the application requirements for GaN-based light-emitting diodes.

A series of orange-red emitting Ba3La(PO4)3:xSm3+ (0.01≤x≤0.30) phosphors was synthesized by the convenient solid-state reaction. X-ray diffraction and photoluminescence spectra were utilized to characterize the structure and luminescence properties of the as-synthesized phosphors. The emission spectra of the Ba3La(PO4)3:Sm3+ phosphors consisted of some sharp emission peaks of Sm3+ ions centered at 563 nm, 600 nm, 647 nm, 710 nm. The strongest one is located at 600 nm due to 4G5/2–6H7/2 transition of Sm3+, generating bright orange-red light. The optimum dopant concentration of Sm3+ ions in Ba3La(PO4):xSm3+ is around 5 mol% and the critical transfer distance of Sm3+ is calculated as 22 A. The CIE chromaticity coordinates of the Ba3La(PO4)3:0.05Sm3+ phosphors was is located in the orange reddish region. The Ba3La(PO4)3:Sm3+ phosphors may be potentially used as red phosphors for white light-emitting diodes.

Undoped and lithium (Li) (1–5 wt%) doped MoO 3 thin films were deposited over ITO coated glass substrates by spray pyrolysis at a substrate temperature of 325 °C. Undoped film was oriented along the 〈0 k 0〉 direction. The texture coefficient value of the undoped film was higher for the (0 2 0) plane compared to other planes of undoped and ‘Li’ doped films. The 100% peak (0 2 1) plane of orthorhombic MoO 3 and hexagonal phase were induced upon doping with ‘Li’. The crystallite size of the undoped film is less compared to the ‘Li’ doped films. The intense Raman peak at 996 cm −1 is due to the terminal oxygen (Mo 6+ = O stretching mode) in the orthorhombic α-MoO 3 phase. The characteristic Mo 3 d 5/2 and 3 d 3/2 doublet caused by spin–orbit coupling are clearly resolved with a splitting of 3.1 eV in the XPS spectra. Scanning electron microscope (SEM) image shows a change in the microstructure, consistent with the change from α-MoO 3 to mixed α and hexagonal phases. Sprout like features were observed in SEM image and rod like features in atomic force microscope (AFM) images. Both direct and indirect band gap showed red shift upon doping with ‘Li’ compared to undoped film as estimated from the transmittance spectra. Intensity of the green photoluminescence (PL) emission spectra was found to quench with ‘Li’ concentration. Cyclic voltammetry result shows that the presence of mixed phases in ‘Li’ doped films decreases the electrochemical performance. Transport study reveals that the carrier concentration and mobility of the ‘Li’ doped films are lower compared to the undoped film which is due to the evolution of hexagonal phase upon doping with ‘Li’. A dye sensitized solar cell (DSSC) was fabricated using undoped MoO 3 film as photoanode and its efficiency is calculated.

The phosphor of CeO2 activated with the trivalent rare-earth Sm3+ ions were synthesized by using a solvothermal method. The CeO2:Sm3+ powders were finally obtained through calcination process sintered in the air at 800-1200 degrees C. The synthesized phosphors were characterized systematically by X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), photoluminescence (PL) and photoluminescence excitation spectra (PLE). The XRD and FE-SEM results reveal that the phosphor exhibit agglomerated spherical shape and with the increase of sintering temperature peaks become sharper and narrower and the crystal sizes also increase, respectively. The room temperature photoluminescence spectra of Sm3+ doped CeO2 powders were recorded on a PTI (Photon Technology International) flurimeter using a Xe-arc lamp with a power of 60 W. The emitted radiation was dominated by the orange light with the characteristic emission of Sm3+ from the transitions of 4G5/2 --> 6H5/2,7/2. The sharp emission properties show that the CeO2 has the potential to serve as a host material for rare-earth doped laser crystal and phosphor material.

The upconversion luminescence properties of ZrO2:Ho3+ and co-doped ZrO2:Ho3+, Yb3+ nanophosphors with various concentrations of Yb3+ ions were synthesized via a solvothermal reaction method. Our samples have a nearby spherical shape and an average crystal size was about 80 nm. For low concentrations of Yb3+ ion, the crystalline structure changed from tetragonal to monoclinic phase as the Yb3+ concentration increased to 3 mol% Yb3+ ions. As the Yb3+ concentration increased to above 5 mol%, ZrO2 nanophosphors displayed a very stable tetragonal phase. The sample shows a strong green (550 nm) and weak red (660 nm) and near infrared (757 nm) upconversion emission corresponding to the transitions of Ho3+:5F4/5S2 --> 5I8, 5F5 --> 5I8 and 5S2 --> 5I7, respectively. The energy transfer (ET) processes between the Ho3+ and Yb3+ ions and the involved mechanisms have been investigated. Experimental results suggest that two-photon upconversion processes are taking place under excitation by a 975 nm.

A series of Zn1−xGa2S4:xMn2+ (0.005 ≤ x ≤ 0.08) phosphors has been synthesized by solid-state reaction at 950 °C for 2 h in a flowing H2S stream. The structural and photoluminescence properties of Zn1−xGa2S4:xMn2+ phosphors have been investigated. Under an excitation wavelength of λex = 336 nm, ZnGa2S4:Mn2+ exhibits a red emission band at about 612 nm owing to the Mn2+ 4T1(4G) → 6A1(6S) transition. The luminescence band shifts to longer wavelength and is accompanied by a decrease in decay time with increasing Mn2+ concentration. The maximum PL intensity of the phosphor is obtained at x = 0.03. The critical transfer distance of Mn2+ is calculated as 21 A. The decay time for ZnGa2S4:0.03Mn2+ is 1.79 ms. The calculated CIE coordinates indicate that ZnGa2S4:Mn2+ has good color purity. Mn2+-activated ZnGa2S4 phosphors have great potential for application in UV white LED and display devices.

Graphene nanosheets functionalized with poly(p-phenylenediamine) (PPDA) were prepared via the in-situ chemical oxidative polymerization using potassium persulphate as a catalyst. Graphene nanosheets were previously prepared by chemical reduction of exfoliated graphite oxide. The structure and morphology of the composite material were characterized by FTIR, XPS, HRTEM, FESEM and XRD, while the thermal and electrical properties were measured by TGA and a four-probe method. FESEM and HRTEM observations indicated that the graphene sheets were encapsulated in the PPDA matrix. Furthermore, the nanocomposites exhibited improved conductivity and thermal stability as compared with pure PPDA.

Through a polyethylene glycol (PEG) assisted hydrothermal method, the REF 3 –KF system materials have been synthesized. The crystalline structure and the morphology of the final products can be divided into three groups. With the molar ratio of REF 3 to KF = 1:0, 1:1, and 3:1 in the final products, the samples crystallize in the hexagonal phase (REF 3 , RE = La, Ce, Pr, and Nd), the cubic phase (KREF 4 , RE = Sm, Eu, Gd, Tb, and Dy), and the tetragonal phase (KRE 3 F 10 , RE = Ho, Er, Tm, Yb, and Y), respectively. The enhanced luminescence of Tb 3+ has been observed in the Ce 3+ /Tb 3+ co-doped samples and the CeF 3 sample. Acting as a probe, the Eu 3+ presents different optical properties in the tetragonal phase of KY 3 F 10 and in the cubic phase of KEuF 4 . In addition, the luminescent concentration effects of Tb 3+ and Eu 3+ have also been observed in KTbF 4 and KEuF 4 samples and the luminescent decay curves prove those.

By using a hydrothermal method, a series of Eu 3+ concentration dependent GdF 3 nanocrystals have been synthesized. The crystalline structures of samples are characterized by XRD patterns, the morphology and size of the samples are illustrated by FE-SEM images, and the optical properties of the samples are presented by PL excitation and emission spectra. The energy transfer from host Gd 3+ to Eu 3+ is observed in the Eu 3+ doped GdF 3 nanocrystals. The optical properties of Eu 3+ and the energy transfer efficiency from host Gd 3+ to Eu 3+ are discussed on the basis of the Eu 3+ concentration dependent integrated PL excitation and emission spectra of Gd 3+ and Eu 3+ . The discussion on optical properties of Eu 3+ and the energy transfer from Gd 3+ to Eu 3+ is meaningful to design and synthesize Gd 3+ based compounds.

Rare earth molybdates R 4 MoO 9 ( R = Y, Gd, and Lu) with Eu 3+ ion-doped were synthesized by solid-state reaction. The phase structure, optical absorption and photoluminescence properties of the as-prepared powder samples were studied. The powder X-ray diffraction patterns indicated that all the compounds crystallized in a hexagonal structure, and the lattice parameters reduced in the order of the ionic radii of R . The UV–visible diffuse reflectance spectra revealed that the compounds had a strong absorption of near-UV light due to the excitation of MoO 6 groups in the host lattices. The energy absorbed by the host lattices could then be transferred to doped Eu 3+ ions, resulting in red emission due to the f – f transitions of Eu 3+ ions. The optical absorption and photoluminescence properties of the compounds indicated that they might be candidates as the color-conversion red phosphors for solid-state lighting.

Lead-free (1-x)(Na0.5K0.5)NbO3-xLiNbO3, i.e., NKN-LNx (x =0.0, 0.1, 0.2, 0.3, 0.4 mol) was prepared using the conventional solid state reaction method. The effects of LN mixing on the ferroelectric properties of NKN-LNx ceramics were studied using a dielectric constant and P-E (Polarization-electric field) measurements. Ferroelectricity was observed in the composition for x approximately varying between 0.0 and 0.4. Minimum remanent polarization 2Pr=5 C/cm 2 was achieved in the composition for x = 0.2. The ferroelectric phase transition temperature TC increased with increasing LN content. The ferroelectric phase transition of NKN-LNx (x ≥ 0.1) is a second-order phase transition, and that of NKN-LNx (x ≤ 0.2) is a first-order phase transition. These results indicate that the ferroelectric phase transition temperature of NKN-LNx change from that of second-order to weak first-order phase transition according to the LN content.

Poly(methylmethacrylate-co-methacrylic acid) were covalently wrapped onto TiO2 nanoparticles through surface thiol-lactam initiated radical polymerization via grafting from approach. Initially, the surface of TiO2 nanoparticles was modified by (3-mercapto)propyl trimethoxysilane to get thiol functionalized TiO2 nanoparticles (TiO2-SH). A radical polymerization of methylmethacrylate and methacrylic acid was subsequently conducted to afford chemically bonded copolymer with TiO2 nanoparticles by employing two component initiating system consisting of TiO2-SH and butyrolactam. The TiO2 nanocomposites were identified by taking advantage of FT-IR, XPS, and EDX. The physical structure of the nanocomposites was studied by using XRD. The morphology of the nanocomposites was investigated by TEM and SEM analyses. TGA scan showed that the inclusion of TiO2 nanoparticles improved the thermal stability of the copolymer to a certain extent. Additionally, dynamic laser light scattering measurement of the TiO2 nanocomposi...

Through a polyethylene-glycol-assisted hydrothermal method, a series of potassium fluoride (KF)-Yttrium (III) fluoride (YF3) system materials have been synthesized. By controlling the reactant ratios of KF: rare earth ions (RE3+), the hydrothermal temperatures, and the pH values of the prepared solutions, the final products can evolve among the orthorhombic phase of YF3 and/or the tetragonal phase of potassium triyttrium decafluoride (KY3F10) and/or the cubic phase of potassium yttrium tetrafluoride (KYF4). The final products are characterized by the x-ray diffraction (XRD) patterns, the field-emission scanning electron microscopy (FE-SEM) images, the energy-dispersive spectroscopy (EDS) patterns, the photoluminescence (PL) spectra, and the luminescent dynamic decay curves. The XRD patterns of the samples suggest the phase evolution of the final products. The FE-SEM images and the EDS patterns prove that. Europium ion (Eu3+) acting as a probe, its PL spectra and the luminescent decay curves all put together prove the phase evolution of the final products. The research can be extended to study the other KF-REF3 system materials.

Ca 2 MgSi 2 O 7 :Eu 3+ films were deposited on Al 2 O 3 (0 0 0 1) substrates by pulsed laser deposition. The films were grown at various oxygen pressures ranging from 100 to 400 mTorr. The crystallinity and surface morphology of the films were examined by X-ray diffraction (XRD) and atomic force microscopy (AFM), respectively. XRD and AFM respectively showed that the Ca 2 MgSi 2 O 7 :Eu 3+ films had a zircon structure and consisted of homogeneous grains ranging from 100 to 400 nm depending on the deposition conditions. The radiation emitted was dominated by a red emission peak at 620 nm. The maximum PL intensity of the Ca 2 MgSi 2 O 7 :Eu 3+ films grown at 300 mTorr was increased by a factor of 1.3 compared to that of Ca 2 MgSi 2 O 7 :Eu 3+ films grown at 100 mTorr. The crystallinity, surface roughness and photoluminescence of the thin-film phosphors were strongly dependent on the deposition conditions, in particular, the oxygen partial pressure.

EuM2S4 (M = Ga, Al) phosphors were synthesized using the solid-state reaction method. The structure and photoluminescence (PL) properties of the phosphors were investigated in detail. XRD pattern results indicated that the two phosphors are isostructures to the orthorhombic structure. The PL spectra showed that the EuGa2S4 and EuAl2S4 phosphors can be excited efficiently by UV-visible light from 350 to 480 nm and that they emit intense green and bluish-green light, with emission bands peaking at 545 and 506 nm, respectively. The fluorescence lifetimes of Eu2+ were calculated to be 0.076 and 0.064 mu s for EuGa2S4 and EuAl2S4, respectively. The thermal quenching temperature was 412K for EuGa2S4. A green LED was fabricated by the combination of a near-UV InGaN chip and the prepared EuGa2S4 phosphor. The EuGa2S4 phosphor exhibits much better green color purity than EuAl2S4. As a result, EuGa2S4 might be a promising green phosphor candidate for solid-state lighting LED technology. (C) 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

Pure CuO and CuO:Fe (10%) thin films were spray deposited on glass, silicon and quartz substrates at 500 °C. XRD patterns confirmed a monoclinic structure with cubic CuFe2O4 impurities. Surface morphology smoothed out on doping with Fe. The direct and the indirect band gaps of pure CuO and CuO:Fe (10%) films estimated from the spectral transmittance data indicated blue and red shifts respectively. X-ray photoelectron spectroscopy revealed the charge states of the elements. The activation energy for conduction was reduced on doping with Fe as estimated from an Arrhenius plot of the temperature-dependent resistivity. The magnetization of the CuO:Fe (10%) films at 300 K showed a hysteresis behavior with large coercivity. The large variation in the coercivity of the films due to pinned-type magnetic behavior may be useful for multilayer switching device applications.

Through a citric acid assisted hydrothermal method, the RE 3+ (RE 3+ = Ce 3+ , Tb 3+ ) doped cubic phase BaGdF 5 nanocrystals with a sphere-like morphology and an average size of 30 nm have been synthesized. The samples show paramagnetic properties at 300 K. The photoluminescence spectra of the obtained samples suggest that the existence of Ce 3+ can dramatically enhance the emission intensity of Tb 3+ due to an efficient energy transfer from Ce 3+ to Tb 3+ . The energy transfer efficiency from Ce 3+ to Tb 3+ , the critical energy transfer distance between Ce 3+ and Tb 3+ , and the energy transfer mechanism of Ce 3+ –Tb 3+ are discussed based on the experimental data and the theoretical analysis.

Ce 3+ /Tb 3+ co-doped series of samples have been synthesized based on a citric acid assisted hydrothermal method. By controlling the hydrothermal treating time, the samples evolve from the Ce 3+ /Tb 3+ co-doped cubic phase KGdF 4 with spherical morphology into the Ce 3+ /Tb 3+ co-doped orthorhombic phase GdF 3 with rhombic shape finally. The X-ray diffraction data illustrate the phase composition modification process of the samples. The field emission scanning electron microscopy and the transmission electron microscopy images suggest the transformation in the morphology of final products. The spectra of the energy-dispersive spectroscopy reveal the constituents of the samples. And the selected area electronic diffraction patterns prove the crystalline phases of the samples. Based on previous studies and the experimental data, one possible phase composition modification process has been summarized. The photoluminescence excitation and emission spectra and the luminescent dynamic decay curves demonstrate the variations in optical properties of the Ce 3+ /Tb 3+ co-doped final products.

Composite materials of multi-walled carbon nanotubes (MWNTs) and a conducting polymer, poly(3-thiophene boronic acid) (PTBA) were prepared by in-situ oxidative polymerization of TBA in the presence of MWNTs and potassium dichromate. The MWNTs which were previously surface functionalized with acid chloride groups were reacted with TBA using a simple "chemical grafting" technique. It was observed that the nanotubes were dispersed uniformly in the pi-conjugated polymer matrix and entrapped by the polymer. The conductivity of the composites was higher than that of the pure polymer from a conventional four-probe technique, which indicates that the fabrication of MWNTs into the polymer matrix significantly improves the conductivity of the polymer due to the intrinsic properties of MWNTs.

Dry etching of p-tetraethylorthosilicate (TEOS) with HF/H"2O in supercritical carbon dioxide (scCO"2) was studied. The etch rate of TEOS increased with HF concentration and reaction temperature, while the concentration of H"2O and processing pressure were found to have little effect on the etch rate. Finally, poly-Si cantilevers with high aspect ratios (1:150) were released using this technique without stiction and residue on the surface.

Based on a citric acid-assisted hydrothermal method, series of Ce3+/Tb3+ activated fluorides have been synthesized. By controlling the amount of KNO3, the final products evolve from the Ce +/Tb + codoped orthorhombic phase GdF3 to the Ce +/Tb + codoped cubic phase KGdF4. The concentration of Ce3+ has great effects on the crystalline phases and the morphologies of final products. The Ce3+ concentration dependent samples illustrate the appearance of the hexagonal phase solid solution CeF3-GdF3-TbF3 in the final products. When the Ce3+ concentration is 20 mol%, the sample Ce20 presents the hexagonal phase CeF3 but the diffraction peaks move to higher degree. The x-ray diffraction patterns suggest the phase evolution of final products, the field emission scanning electron microscopy images present the variation in morphology of samples, and the photoluminescence excitation and emission spectra as well as the luminescent dynamic curves illustrate the optical properties of samples.

5 mol% Eu 3+ doped NaYF 4 (α-, β-), YF 3 , YF 3 ·1.5NH 3 , NaGdF 4 , and LaF 3 micro/nanocrystals have been synthesized by a hydrothermal method. The final products are characterized by X-ray diffraction, field emission scanning electron microscopy, photoluminescence excitation and emission spectra, and luminescent dynamic decay curves. Due to its sensitivity to local symmetry, Eu 3+ shows different optical properties in the above samples. It has stronger luminescent intensity in β-NaYF 4 than that in α-NaYF 4 while it exhibits different higher energy 5 D 1,2 to lower 7 F J emissions as well as the asymmetric ratios and the splits of 5 D 0 → 7 F 1 , 7 F 4 . YF 3 , LaF 3 , and β-NaGdF 4 have analogous optical intensities to those of β-NaYF 4 . However, β-NaGdF 4 has the similar spectral profile to that of β-NaYF 4 while YF 3 and LaF 3 have the opposite cases in the 5 D 0 → 7 F 2 , 7 F 1 emissions. Further, Judd–Ofelt calculation has been used to analyze the experimental phenomena.

Single walled carbon nanotube (SWNT)/graphene oxide (GO) hybrid films were prepared by a facile bar coating method on a polyethylene terephthalate substrate using a mixed solution of SWCNTs and GO. An acryl type polymer was employed as a dispersion agent to obtain SWCNT and GO suspension in ethyl alcohol. The SWCNT/GO hybrid films were highly transparent and electrically conductive, showing 80% transmittance and 1.8 x 10(3) ohm/sq surface resistance. The surface resistance of the SWCNT/GO film could be further improved to 750 ohm/sq by hydrazine vapor reduction.

In display applications, each displays technique needs different phosphors according to its applications. So, in this paper, nano-sized red emitting CaTiO3:Pr3+ powder phosphors were prepared by solvothermal reaction method. The phase purity and the structure of the phosphors were characterized by X-ray diffraction (XRD), field emission scanning electron microscope (FE-SEM). The particles show the spherical morphology, which indicates the good luminescent characteristics. The luminescent properties of CaTiO3:Pr3+ powder phosphors have been carried out by the measurement of their phototluminescence (PL) and phototluminescence excitation (PLE) spectra. The PL spectra shows the strong red emission due to 1D2 --> 3H4 transition. The emissions of intra-4f transitions from the excited states (1D2) to the ground state (3H4) of Pr3+ are mainly observed around from 612 to 618 nm. The effect of the Pr3+ concentration on their photoluminescent properties was investigated extensively. These luminescent powders are expected to find potential applications such as optical display systems.