Search

To optimize the process and obtain highly conducting and transparent Aluminum-doped zinc oxide (AZO) thin films, AZO films were deposited on glass substrates at room temperature by Radio-frequency (RF) magnetron sputtering with various Argon flow rates. The influences of Argon flow rate on structure, morphology, optical, electrical and photoluminescence properties of AZO films were investigated by varying the Argon flow rate from 36 to 68 sccm. The best quality AZO film with resistivity 1.39 × 10−3 Ω cm, sheet resistance 8.2 Ω/sq and 84.2% average visible transmittance was prepared at 44 sccm for 30 min. Also, the self-heating effect of target was investigated by preparing AZO films for 10 min and 20 min at 44 sccm, 180 W and 1.0 Pa. The influence of increasing structural quality actually affected by Argon flow rate was more prominent on carrier concentration than mobility. The schematic illustration of microstructural evolution was proposed. The average growth rate of around 60 nm/min demonstrated the self-heating effect of target was weak and could be ignored.

In this study, negative temperature coefficient (NTC) ceramics based on CaCu3Ti4-xZrxO12(0 ≦ x ≦ 0.15) compositions have been successfully synthesized by traditional solid-state method. X-ray diffraction results show that the major phase of all samples is CaCu3Ti4O12 (CCTO) phase with body-centered cubic structure. The substitution of Zr4+ for Ti4+ inhibits the grain growth of CaCu3Ti4-xZrxO12 ceramics and greatly reduces the grain size. The results of X-ray photoelectron spectroscopy fully confirm the coexistence of Cu+/Cu2+ and Ti3+/Ti4+ ions, which are one of the important reasons for conductivity of CaCu3Ti4-xZrxO12 samples. There is a good linear relationship between the natural logarithm of resistivity and reciprocal temperature of all ceramic samples, which is consistent with NTC behavior. The obtained values of ρ150, B150/550 and Ea of the sintered samples are in the range of 1.62 × 105–3.39 × 105 Ω cm, 6378–6593 K and 0.550–0.568 eV, respectively.

Ca₂Gd₈(SiO₄)₆O₂:A (A = Eu³⁺ and Dy³⁺) phosphors were successfully synthesized by the sol-gel process. X-ray diffraction (XRD), thermogravimetric and differential thermal analysis (TG-DTA), Fourier transform infrared spectroscopy (FT-IR), transmission electron microscopy (TEM), and photoluminescence spectra were used to characterize the resulting phosphors. The results of XRD indicated that the diffraction peaks of the phosphor powder agreed well with the standard card. Under short ultraviolet excitation, the doped rare earth ions (A) showed their characteristic emis- sions in Ca⁺Gd₈(SiO₄)₆O₂ phophors, i.e., ⁵D₀ --> ⁷F₂ (615 nm) for Eu³⁺ and ⁴F₉/₂2 --> ⁶H₁₅/₂ (483 nm) and ⁴F₉/₂ --> ⁶H₁₃/₂ (575 nm) for Dy³⁺. The optimum concentration for doped rare earth ions was determined to be 9 mol% Eu³⁺ and 3 mol% Dy³⁺ of Gd³⁺ in Ca₂Gd₈(SiO₄)₆O₂

There are growing interests on phosphor thin films owing to their potential application in high-resolution devices such as cathode ray tubes and flat panel display devices. The solution-based sol-gel method is one of the most important techniques for the synthesis of various functional coating films. Compounds with the apatite structure are very suitable host lattices for various luminescent ions. Ca 2 RE 8 (SiO 4 ) 6 O 2 (RE=Y, Gd, La) is a kind of ternary rare-earth-metal silicate with oxyapatite structure, which has been used as host material for the luminescence of various rare earth and mercury-like ions. In this article, Ca 2 Gd 8 (SiO 4 ) 6 O 2 :Dy 3+ phosphor films were dip-coated on quartz glass substrates through the sol-gel process. X-ray diffraction (XRD), atomic force microscopy (AFM), photoluminescence (PL) spectra, as well as lifetimes were used to characterize the resulting films. AFM study revealed that the phosphor films consisted of homogeneous particles. The Dy 3+ showed its characteristic emission in crystalline phosphor films, i.e., 4 F 9/2 – 6 H 15/2 and 4 F 9/2 – 6 H 13/2 .

Ca2RE8(SiO4)6O2:A (RE=Y, Gd; A=Pb2+, Mn2+) phosphor films were dip-coated on quartz glass substrates through the sol-gel process. X-ray diffraction (XRD), photoluminescence (PL) spectra as well as lifetimes were used to characterize the resulting films. Under short wavelength UV excitation, the film showed a red emission with medium intensity. The decay curve of Mn2+ luminescence in Ca2Gd8(SiO4)6O2:Pb Mn film could be fitted into a single exponential function. The lifetime of Mn2+ was 10.21 ms in Ca2Gd8(SiO4)6O2.

Ca 2 RE 8 (SiO 4 ) 6 O 2 (RE = Y, Gd, La) is a kind of ternary rare-earth-metal silicate with the oxyapatite structure, which was used as host materials for the luminescence of various rare earth and mercury-like ions. Ca 2 Gd 8 (SiO 4 ) 6 O 2 :Er 3+ phosphors were prepared through the sol-gel process. X-ray diffraction (XRD), scanning electron microscopy (SEM) and photoluminescence spectra were used to characterize the resulting phosphors. The results of XRD indicate that the phosphors crystallized completely at 1000 °C. SEM study reveals that the average grain size is 400 ∼ 1000 nm. In Ca 2 Gd 8 (SiO 4 ) 6 O 2 : Er 3+ shows its characteristic green emission at 528 nm ( 2 H 11/2 - 4 I 15/2 ) and 548 nm ( 4 S 3/2 - 4 I 15/2 ) upon excitation into 382 nm, with an optimum doping concentration of 5% (mole fraction) of Gd 3+ in the host lattices.

We synthesize MAl12O19 (M = Ca, Sr, Ba) singly doped with Eu2+ or Cr3+ and co-doped with Eu2+ and Cr3+ by high-temperature solid-state reaction under reducing atmosphere. It is observed that there exit energy transfers from Eu2+ to Cr3+ in MAl12O19 (M = Ca, Sr, Ba) hosts. Although the MAl12O19 (M= Ca, Sr, Ba) hosts have similar crystal structures, the energy transfer efficienies and the conversion rates of the blue light to the red light are different. Both experiment and calculation show that the energy transfer from Eu to Cr in CaAl12O19 host is most efficient, and the ratio of the red emission to the blue emission in CaAl12O19 host is the highest among the three different hosts.