La2O3 Powders Research Articles

Preparation and properties of La and Nb co-doped TiO2 colossal dielectric ceramic materials

In this study, La + Nb co-doped TiO2 (LNTO; x = 0, 0.02, 0.05, 0.07) ceramics were prepared by the solid-state reaction method with high-purity TiO2, La2O3 and Nb2O5 powders. LNTO ceramics show dense microstructures with the second phase at the grain boundary, and La and Nb addition can inhibit the grain growth. Results of dielectric properties show that the dielectric constant of LNTO ceramics are enhanced largely (e′ > 104) and that the dielectric loss is relatively low (tan δ ~ 0.1) compared with that of pure TiO2 (e′ ~ 102) at low frequency. Within the test temperature range (30–500 °C) and test frequency range (0.5–1000 kHz), dielectric constants of LNTO ceramics display relatively high stability. The two peaks in modulus spectra could be explained by Maxwell–Wagner polarization. The results of dielectric and impedance spectra prove that the internal barrier layer capacitance model can be used to explain the colossal permittivity in (La + Nb) co-doped TiO2.

Impact of inversion symmetry on a quasi-1D S = 1 system

Here, we report the synthesis and magnetic properties of a novel, centrosymmetric, quasi-1D spin chain system La3VWS3O6, with hexagonal crystal structure (P63/m, a = 9.460 76(3), c = 5.518 09(2) Å). Pure powders were obtained by solid-state reactions from La2O3, WO3 and metal powders of V and W. X-ray powder diffraction, specific heat, magnetization, 139La-nuclear magnetic resonance (NMR), and electric resistivity measurements indicate that the compound is a low dimensional magnet with an S = 1 spin chain that exhibits no sign of magnetic ordering above 2 K. A single ion anisotropy (D/kB ~ 10 K), caused by magneto-crystalline effects, is probably responsible for a thermodynamic entropy release at lower temperatures, which concurs with 139La-NMR data. By detailed comparison with non-centrosymmetric Ba3V2S4O3, having a very similar magnetic lattice, it is obvious that the presence of crystallographic inversion symmetry has an effect on the behaviour of the magnetic chains.

Effect of La2O3 on the Microstructure and Grain Refining Effect of Novel Al-TiO2-C-XLa2O3 Refiners

New aluminum grain refiners, Al-TiO2-C-XLa2O3 refiners, were manufactured by the in situ reaction of Al powder, TiO2 powder, C powder, and La2O3 powder. The effects of La2O3 on the refiners’ microstructure and the grain refining effect of the Al-TiO2-C-XLa2O3 refiners on industrial aluminum were studied. The effect of the sintering process was also studied. The results show that the refiners contain Al3Ti, TiC, Al2O3, AlN, and Al20Ti2La. As the content of La2O3 increases, the amount of Al20Ti2La also increases. However, the amounts of Al3Ti, Al2O3, and TiC decrease. Al3Ti is a lath-like compound whose size becomes smaller. The distribution of Al2O3 and TiC, however, is more uniform. The Al-TiO2-C-0.2La2O3 refiner has the best grain refining effect on industrial aluminum. The size of the industrial aluminum refined by the Al-TiO2-C-0.2La2O3 refiner is 320 μm; the refiner’s grain size is 8.4% that of the industrial aluminum without refiners 0 μm (380). After adding the novel Al-TiO2-C-0.2La2O3 refiner, the nucleation temperature TN reached 679.21 °C, which is 17 °C above the nucleation temperature of the industrial aluminum without refiners. The primary transformation time is the longest at 25.5 s, which is 4.6 s higher than that of industrial aluminum (20.9 s). Furthermore, the ΔT of the aluminum is 0.5 °C, which is the lowest value.

Interaction of Yttrium, Lanthanum, and Samarium Oxides at 1600°C

Phase equilibria and structural transformations in the La2O3–Y2O3–Sm2O3 system at 1600°C were studied by X-ray diffraction and petrography over the entire composition range. Solid solutions based on the hexagonal (A) modification of La2O3, cubic (C) modification of Y2O3, and monoclinic (B) modification of La2O3 (Sm2O3) were found to form in the system. The starting materials were La2O3, Sm2O3, and Y2O3 (99.99 %) powders. The samples were prepared from nitrate solutions with subsequent evaporation and decomposition at 800oC for 2 h. The samples were subjected to heat treatment in three stages: at 1100°C (for 2464 h), at 1500°C (for 50 h), and then at 1600°C (for 10 h) in furnaces with Fechral (H23U5T) and Superkanthal (MoSi2) heating elements, respectively. The isothermal section of the La2O3–Y2O3–Sm2O3 phase diagram at 1600°C is characterized by three single-phase (A-La2O3, B-La2O3 (Sm2O3), C-Y2O3) and two-phase (A + B, B + C) regions. The ordered phase of perovskite-type was not found at 1600°C in this system. An infinite series of solid solutions based on the monoclinic modification of B-La2O3 (Sm2O3), which occupies the largest area of the isothermal section, forms in the system. Yttrium oxide stabilizes the total mutual solubility of lanthanum and samarium oxides. The lattice parameters of the B phase decrease, the lattice volume increases with the addition of a heavier ion, and the lattice of solid solutions based on the B modification of rare earth metal oxides becomes more densely packed with higher yttrium oxide. The lattice parameters of the B phase lattice vary from a = 1.3988 nm, b = 0.3774 nm, and c = 0.8427 nm in the single-phase sample containing 15 mol.% Y2O3–42.5 mol.% La2O3– 42.5 mol.% Sm2O3 to a = 1.3806 nm, b = 0.3709 nm, and c = 0.8312 nm in the two-phase sample containing 45 mol.% Y2O3–27.5 mol.% La2O3–27.5 mol.% Sm2O3.

Synthesis of high-performance Mo–La2O3 powder by hydrogen reduction of MoO2 originated from a self-reduction strategy

A traditional preparation process of Mo powder is generally time-consuming and leads to coarse particles. In this work, we propose a short-flow strategy, in which the intermediate product of MoO2 is prepared by a one-step self-reduction method in air instead of a mixture of decomposition and hydrogen reduction processes. And the reaction mechanism of self-reduction is investigated and the consequent sintering performance of Mo powder is also compared with the traditional one. The obtained results demonstrate that the finally synthesized Mo–La2O3 powder prepared by the self-reduction strategy are spherical with an average particle size of 2.03 μm, exhibiting an excellent sintering performance with a relative density of 95.3% and a hardness of 260.6 (HV), better than those by a traditional one (93.4% and 232.4 (HV)), which can be attributed to smaller particle size and better shapes. This work provides a new route for the synthesis of Mo–La2O3 powder, indicating a possible industrial application.

Enhanced fracture toughness and toughening mechanisms of fine-grained Mo–12Si–8.5B alloy with a bi-modally structured α-Mo grain

Fine-grained Mo–Si–B alloys possess superior strength and oxidation resistance at high temperature, but they usually exhibit poor toughness at room temperature. Improvement of toughness is critical to the practical application of alloys. Here, a series of fine-grained Mo–12Si-8.5B-0.57 wt% La2O3 alloys with bi-modally structured α-Mo grains were fabricated by hot pressing sintering of a mixture of ball milled Mo–Si–B–La2O3 powders and unmilled Mo–La2O3 powders in select proportion. When the mass fraction of unmilled Mo–La2O3 powders was 15%, the sintered alloy showed an optimal microstructure consisting of a continuous bimodal fine-grained (~0.62 μm)/coarse-grained (~3.06 μm) α-Mo matrix with embedded Mo3Si/Mo5SiB2 (~0.52–0.54 μm) particles. This bimodal-structural alloy displayed high yield strength (2460 MPa) and compression strength (2561 MPa) together with significant enhanced fracture toughness (12.5 MPa m1/2). The high strength resulted from the contributions of fine α-Mo grains and nanometer La2O3 particles, meanwhile the improved toughness might be attributed to (1) coarse-grained α-Mo regions promoting crack trapping, (2) the formation of intragranular microcracks within the coarse-grained α-Mo regions induced by La2O3, (3) occurrence of the α-Mo/intermetallic interface debonding.

Effect of La2O3 addition on copper matrix composites reinforced with Al2O3 ceramic particles

La2O3, Al, and CuO powders were used as raw materials and pure copper as a matrix; La2O3 was added to an Al–CuO system to form a new La2O3–Al–CuO reaction system. The copper matrix composites were prepared by an in situ synthesis technique and the near-melting casting method. The in situ reaction products, and the morphology, size, and distribution of the composites were observed by scanning electron microscopy, energy dispersive spectroscopy, and transmission electron microscopy, while the effect of La2O3 on the reaction products of the Al–CuO system and on the microstructure, hardness, and conductivity of the composites were studied. The results show that the size and morphology of the Al2O3 particles changed significantly after the addition of La2O3. The size of the Al2O3 particles was reduced to the nanometer scale, while the morphology changed from spherical to irregular-shaped, and the Al2O3 particles were evenly dispersed in the Cu matrix. The resulting grains were finer and more uniform, and the electrical conductivity and hardness of the composites were obviously improved. When 0.6 wt% La2O3 of matrix was added, the electrical conductivity reached 90.2% IACS and the hardness reached 87.9 HV. Compared with the composite prepared by the Al–CuO system, the electrical conductivity and hardness of that prepared by the La2O3–Al–CuO system increased by 7.8% and 8.7%, respectively.

Facile preparation and characterization of lanthanum oxide powders by the calcination of lanthanum carbonate hydrate in microwave field

Micron-sized lanthanum oxide powders are prepared by the calcination of lanthanum carbonate hydrate in microwave field. The decomposition process of lanthanum carbonate hydrate was analyzed by TG-DSC and indicates the reaction undergoes three stages, resulting in the generation of lanthanum oxide at 770 °C. For microwave assisted calcination, XRD patterns demonstrate that hexagonal La2O3 structure is initially formed after calcination at 650 °C for 2 h, and FT-IR analyses confirm the decomposition of precursor is complete after calcination at 750 °C for 2 h. SEM investigations reveal that 800 °C is the optimal calcination temperature to generate La2O3 powders with uniform morphologies. In comparison, conventionally calcination experiments are carried out in electrical furnace. Both XRD and FT-IR analyses are in consistence with TG-DSC, which indicate the temperature required for fully decomposition of lanthanum carbonate hydrate by conventional heating is higher than that of microwave heating. SEM images present irregular morphologies and wide particle size distribution of conventionally prepared samples. All the techniques are utilized to prove the feasibility of decomposing La2(CO3)3 to generate La2O3 in microwave field and highlight the advantages of microwave heating.

Cathodoluminescence degradation of Bi doped La2O3 and La2O2S phosphor powders

Simultaneous cathodoluminescence (CL) and Auger electron spectroscopy (AES) measurements were performed on La2-xO3:Bix=0.002 and La2-xO2S:Bix=0.002 phosphor powders during long term exposure to an electron beam in order to assess the CL degradation and chemical changes on the surface. X-ray photoelectron spectroscopy (XPS) measurements were also made before and after CL degradation. After a small amount of initial CL degradation, the La2-xO3:Bix=0.002 sample remained stable under the electron beam and it may be suitable for use in field emission displays. However, the La2-xO2S:Bix=0.002 showed continuous and severe CL degradation and is not suitable for CL applications. During degradation AES measurements showed that there was a decrease in the surface concentration of S, suggesting the formation of a non-luminescent La2O3 surface layer which was responsible for degradation. However, some S remained on the surface and XPS spectra showed that a sulphate, possibly La2O2SO4, was present which may have contributed to the degradation.

Enhancing mechanical properties and air permeability of corundum porous materials by in situ formation of LaAl11O18 in bonding phase

Corundum porous materials of particle-packing type with different contents of in situ formed LaAl11O18 were prepared using tabular corundum, reactive alumina and La2O3 powder as raw materials. The effects of the introduction of LaAl11O18 on the microstructure, phase composition and properties of the porous materials were investigated. The specimens were characterized by scanning electron microscopy, X-ray diffraction and mercury porosimetry. Results show that platelet-like LaAl11O18 is formed in situ by the reactions of La2O3 and Al2O3. With a certain amount of La2O3 added, the cold crushing strength, cold modulus of rupture and hot modulus of rupture (1400 × 0.5 h) of the specimens are increased, and the air permeability is improved simultaneously. However, upon further increasing the amount of La2O3 added, the mechanical properties and air permeability of the porous materials then decrease gradually owing to the increased numbers of pores and cracks in the bonding phase. The enhanced mechanical properties of the specimens with La2O3 added are attributed to the strengthening effects of plate-like LaAl11O18 in the bonding phase and to the activated sintering of both Al2O3 powder and corundum coarse aggregate for the diffusion of La3+ in Al2O3 lattice. In addition, the improved air permeability of the specimens should be related to the decreased content of pores in the bonding phase and the reduced number of interfacial cracks.

Dielectric Properties of Porous Reaction-Bonded Silicon Nitride with Different Additives

The influence of additives on the dielectric properties of porous silicon nitride ceramics with 0.6-mm apertures and 56% porosity prepared by reaction sintering has been studied. The results show that high porosity and large apertures in porous silicon nitride ceramics lower the dielectric constant and dielectric loss compared with dense silicon nitride ceramic. α-Si3N4 additive is beneficial to decrease the dielectric constant and dielectric loss. Addition of Y2O3 and La2O3 powders may result in formation of Y-Si-O-N and La-Si-O-N phases, and enhance the volume fraction of β-Si3N4 phase. The transition of Y3+ and La3+ weakly associated ions and vacancies in the Y-Si-O-N and La-Si-O-N systems leads to higher dielectric constant and dielectric loss.

Magnetic Ordering of Perovskite-Like La-, Nd-, and Gd-Doped Bismuth Ferrite

ABSTRACTBismuth ferrite (BiFeO3) and La-, Nd- and Gd-substituted bismuth ferrite of the Bi1-xLaxFeO3, Bi1-xNdxFeO3, and Bi1-xGdxFeO3 types with the atomic part of the substitution element x equal up to 0.20 were synthesized by the solid-state reaction method using powders of oxides Bi2O3, Fe2O3, and La2O3, or Nd2O3, or Gd2O3 of pure grade quality and investigated using X-ray diffraction analysis. The magnetization was measured in the magnetic field up to 6.5⋅106 A/m at 5 and 300 K. It was found that the total substitution up to 0.20 atomic part of Bi by La, Nd, and Gd leads to the paramagnetic behavior of the doped bismuth ferrite at low temperatures in a wide range of magnetic field. Strong nonlinear dependence of magnetization on the magnetic field was detected and a ferromagnetic-like dependence of magnetization was observed for small magnetic fields. This can be explained by the exchange interaction between doping magnetic ions, as well as by the exchange interaction of these ions with ions of iron. The enhancement of magnetic properties with the increase of the content of the substitution is monotone and is more pronounced for the Bi1-xGdxFeO3 ceramics.

Stability of Bi doped La2O3 powder phosphor and PMMA composites

Bismuth (Bi) ions exhibit interesting optical properties, yet they have been less intensively studied compared to rare earth ions. Blue emitting Bi doped lanthanum oxide (La2O3:Bi) phosphor was synthesized using the sol-gel combustion method at 250 °C using citric acid as the fuel, followed by annealing at 1200 °C in air for 2 h. X-ray diffraction (XRD) data confirmed that the phosphor powder crystallized in a hexagonal lattice, but after storage of several weeks revealed that the La2O3 had changed to La(OH)3. If the transformed samples were re-annealed in air at 800 °C for 2 h, XRD results showed that the structure reverted completely to La2O3 and the blue PL emission was once again observed, however at only about one third of the intensity as for freshly prepared samples. For samples stored in a vacuum desiccator for one week, no change for XRD and PL were observed. Degradation was effectively slowed, but not eliminated, by encapsulation of the phosphor in poly(methyl methacrylate) polymer.

Effect of La2O3 on the in-situ reaction products in Al–CuO–Ti–C system

The Aluminum Matrix Composites were manufactured by in situ reactive near liquidus cast of La2O3 powder, aluminum powder, CuO powder, Ti powder, graphite powder with 6063 aluminum alloy as the matrix using the contact reaction method. The x-ray Diffraction, Differential Scanning Calorimeter, Scanning Electron Microscope and Energy Dispersive Spectroscopy were utilized to study the phase evolution and observe the morphology and distribution of the in situ products. The effect of La2O3 on the in situ reaction products in Al–CuO–Ti–C system was investigated. The results manifest that the microstructure of the in situ reaction products in the Al–CuO–Ti–C system is composed of needle-like and lath-like Al3Ti phase, nearly globular-like Al2O3 and granular-like TiC. The microstructure of the in situ reaction products in the Al–CuO–Ti–C-La2O3 system is composed of blocky-like and short rod-like Ti2Al20La phase, globular-like Al2O3 and granular-like TiC. By comparing the two systems, the addition of La2O3 eliminates the needle-like Al3Ti phase of 120 μm and the agglomerated lath-like Al3Ti phase of 50 μm, forms the blocky-like and short rod-like Ti2Al20La of under 20 μm. At the same time, it improves the agglomeration phenomenon of TiC and Al2O3 particles, making them more diffusely distributed in the matrix. The size of TiC and Al2O3 particles reduces from 1 μm to 0.5 μm and 5 μm to 1 μm, respectively.

Luminescence properties of Bi doped La2O3 powder phosphor

Different concentrations of bismuth doped lanthanum oxide (La2-xO3:Bix) phosphor powder (x = 0.001, 0.002, 0.003, 0.004, 0.006, 0.008 and 0.01) were synthesized by means of the sol-gel combustion method at 250 °C using citric acid as the fuel. The product was annealed at different temperatures and the luminescence properties were investigated. The maximum emission was obtained for the sample which was doped with x = 0.002 and annealed at 1200 °C in air. The X-ray diffraction analysis confirmed that all samples crystallized in the La2O3 hexagonal phase. The scanning electron microscopy data showed that the grain size increased with increasing annealing temperature and the shape of the grains changed from rectangular to more round, but faceted, after annealing at 1200 °C in air. Energy dispersive X-ray spectroscopy confirmed the chemical composition, while diffuse reflectance spectroscopy was used to study the absorption of the La2-xO3:Bix samples. All the samples were absorbing in the ultraviolet range between 220 and 320 nm. The band gap of the La2O3 pure host sample was obtained from the reflectance data as 5.1 eV. Excitation at a wavelength of 308 nm resulted in a single broad blue luminescence emission band centered at 462 nm. The excitation and emission bands were attributed to transitions between the 1S0 ground state and the 3P1 excited state of Bi3+ ions, with a Stokes shift of 1.35 eV.

Grain growth kinetics and growth mechanism of columnar Al2O3 crystals in xNb2O5–7.5La2O3-Al2O3 ceramic composites

xNb2O5–7.5La2O3-Al2O3 ceramic composites with in-situ-grown columnar Al2O3 crystals were successfully prepared by microwave sintering at 1450–1525 °C using α-Al2O3, Nb2O5, and La2O3 powders as raw materials. X-ray diffraction results indicated that the main phases were Al2O3, LaNbO4, and Nb2O5 in the prepared samples. A field emission scanning electron microscope (FESEM) showed that the Al2O3 crystals appeared as columnar in the structure. Moreover, the grain size of the columnar Al2O3 crystals increased with the Nb2O5 content. The ratio of the major axis to the minor axis of the crystals was largest when the Nb2O5 content was 15 vol%. Furthermore, the grain-growth kinetics index (n), growth activation energy (Q), and growth mechanism of the columnar Al2O3 crystals were studied. The results indicated that the Nb2O5 addition could promote formation and growth of columnar Al2O3 crystals, and the grain-growth activation energy indicated that the dissolution process controls the crystal growth. The growth mechanism of the columnar Al2O3 crystals was also studied. The present work demonstrated that Nb2O5 is a good additive for the preparation of Nb2O5–7.5La2O3-Al2O3 composite ceramics with columnar Al2O3 crystals.

Influence of calcination on the sol–gel synthesis of lanthanum oxide nanoparticles

A facile sol–gel technique was employed to synthesize lanthanum oxide nanoparticles (hereafter La2O3 NPs) using micro-sized La2O3 powders, 20% nitric acid, and high-molecular weight polyethylene glycol (PEG) as raw materials. The synthesized La2O3 NPs were calcined at 750, 900, and 1000 °C in air for 2 h. The calcined products were characterised using numerous experimental techniques, namely X-ray diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDXS), thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), Fourier-transform infrared (FTIR) spectroscopy, and photoluminescence (PL) spectroscopy. The experimental results indicated that the calcination temperatures have remarkable effects on the crystallinity, particle size, and lattice strains of the La2O3 NPs. The XRD patterns confirmed the hexagonal phase of the La2O3 NPs with lattice constants: a = b = 0.3973, nm and c = 0.6129 nm. The average crystallite size of the La2O3 NPs estimated by electron miscroscopy was in good agreement with the XRD results. The degree of crystallinity, and the average crystallite size of the NPs were increased, while the lattice strains were decreased with the calcination temperatures. The photoluminescence spectra of nanoparticles illustrated a strong emission band at the vicinity of 364 nm, which is typically known to be the green band for La2O3 NPs.

Preparation and synthesis thermokinetics of novel Al-Ti-C-La composite master alloys

The new type of Al-Ti-C-La master alloy was prepared by commercial pure Al, Ti powder, graphite powder, Al powder and La2O3 powder by aluminum melt in-situ reaction method. The microstructure and the effect on commercial pure aluminum of Al-Ti-C-La master alloy have been studied by means of X-ray diffraction (XDR), scanning electron microscopy (SEM) equipped with energy-dispersive spectrometry (EDS). The synthesis thermodynamics and kinetics of Al-Ti-C-La master alloy were analyzed. The experiment shows that Al-Ti-C-La master alloy is composed of Al, Al3Ti, TiC and Ti2Al20La. The refining performance of the prepared Al-Ti-C-La master alloy is obviously better than that of Al-Ti-C master alloy when the addition of rare earth oxide La2O3 is 10 wt% and the preparation temperature is 930 °C. The analysis of thermodynamic calculation and the process of kinetics demonstrate that, in the preparation process of Al-Ti-C-La master alloy, firstly, Al reacts with Ti to produce Al3Ti, C reacts with Ti and Al3Ti to form TiC based on the aluminothermy reaction. Rare earth oxide La2O3 and C powder react with Ti powder and O2 in the air occur to generate CO, TiC, [La] atoms and LaC2. [La] atoms adsorb on the surface of Al3Ti to form the new rare earth compounds Ti2Al20La.

Dispersion Effect of LaPO4 Particles in Lithium Ion Conductor LATP

Introduction In recent years, increasing efforts have been focused upon the developments of all solid-state batteries. As for the solid electrolyte, while sulfide-based systems represent excellent lithium ion conductivity, oxide-based systems still have an advantage in a stability in air. Therefore, it is greatly recommended to improve the conductivity of lithium ion conductive oxides. We have reported that lithium ion conductivity is enhanced by introducing LLTO (La2/3-xLi3xTiO3) particles in LATP (Li1.3Al0.3Ti1.7(PO4)3) matrix [1] as shown in Fig. 1. The d.c. electrolysis using stainless-steel / electrolyte / metallic lithium asymmetry cell confirmed the transport number of lithium ion as unity. While the sample was obtained by co-sintering the precursor of LATP and LLTO particles, X-ray diffraction suggested that LLTO was decomposed into LaPO4. Then, we thought that dispersion of LaPO4 attribute to the enhancement of lithium ion conductivity. Nevertheless, when LaPO4 particle was employed as a starting member for co-sintering, conductivity enhancement was not observed, which is presumably due to the particle size growth of LaPO4. The precise size of LaPO4 formed from LLTO is uncertain from the back-scattered electron images of SEM. In addition, titanium component decomposed from LLTO might attribute to the conductivity enhancement for LATP. In the present study, LaPO4 particle dispersed in LATP-LLTP composite is confirmed by TEM observation. Thereafter we prepare the LATP-La2O3 composite to clarify that the conductivity enhancement of LATP-LLTO composite is not caused by the titanium introduction into LATP but simply the insulator-dispersion effect in lithium ion conductors. Experimental Sample preparation has been carried out according to the previous study [1]. Li0.35La0.55TiO3 (LLTO) was prepared by the conventional solid-state reaction method sintered at 1300oC, thereafter crushed and milled finely by using planetary ball mill. LATP precursor was synthesized by calcining Li2CO3, γ-Al2O3, TiO2 and (NH4)H2PO4 starting materials at 700oC for 2 hours. The obtained LATP precursor was then mixed with LLTO particles or La2O3 powders (d < 100 nm) and milled for 1 hour with as small amount of ethanol. After drying, the composites are pressed into pellets and sintered at 1000oC. Results and Discussions Fig. 2 shows the TEM images of the dispersed particles. From the EDX analyses, the composition of the particle is confirmed as LaPO4. In addition, typical particle size is found to be 200 nm. Any void was not observed at the interface between LaPO4 and LATP matrix. As for the LATP-La2O3 composites, the introduced La2O3 appeared to be reacted into LaPO4, since X-ray diffraction indicated the absence of La2O3 and formation of LaPO4 in the composites. Fig. 3 shows the compositional dependence of conductivity for LATP-La2O3 composite measured at room temperature. Although the maximum conductivity is smaller than that of LATP-LLTO, conductivity is increased by introducing La2O3 with the maximum at 8wt% of La2O3 addition. Accordingly, the conductivity enhancement observed in these system is surely due to the insulator-dispersion effect as observed in LiI-Al2O3 system [2].

The feasibility of using solution-processed aqueous La2O3 as effective hole injection layer in organic light-emitting diode

Low-cost and scalable manufacturing boosts organic electronic devices with all solution process. La2O3 powders and corresponding aqueous solutions are facilely synthesized. Atomic force microscopy and scanning electron microscopy measurements show that solution-processed La2O3 behaves superior film morphology. X-ray diffraction and X-ray photoelectron spectroscopy measurements verify crystal phase and typical La signals. In comparison with the most widely-used hole injection layers (HILs) of MoOx and poly(ethylene dioxythiophene):poly(styrene sulfonate) (PEDOT:PSS), enhanced luminous efficiency is observed in organic light-emitting diode (OLED) using solution-processed La2O3 HIL. Current-voltage, impedance-voltage and phase angle-voltage transition curves clarify that solution-processed La2O3 behaves nearly comparable hole injection capacity to MoOx and PEDOT:PSS, and favorably tailors carrier balance. Moreover, the hole injection mechanism of solution-processed La2O3 is proven to be predominantly controlled by Fowler-Nordheim tunneling process and the hole injection barrier height between ITO and NPB via La2O3 interlayer is estimated to be 0.098 eV. Our experiments provide a feasible application of La2O3 in organic electronic devices with solution process.