Terbium Oxide Research Articles

Unusually large structural stability of terbium oxide phase under high pressure

Abstract High-pressure X-Ray diffraction studies on terbium oxide have been carried out up to a pressure of ∼35 GPa in a diamond anvil cell at room temperature. Terbium oxide, which exhibits the fluorite structure at ambient conditions, remains stable in its fluorite form up to a pressure of ∼27 GPa. Above 27 GPa, it undergoes a structural phase transition accompanied with broadening and appearance of new diffraction peaks. The large structural stability of the compound under pressure is thus unusual when compared with other rare earth sesquioxides, and has been attributed to the presence of Tb4+ ions. The XPS spectra on the sample confirms the presence of Tb4+ ions. The bulk modulus and its pressure derivative of the parent phase are evaluated and reported.

Sensor composites consisting of a ceramic substrate and thin films of TbO x oxides and (TbO x )0.5(YO1.5)0.5 solid solutions

A porous nanoceramic material based on aluminum magnesium spinel is synthesized. Films based on terbium oxide and the (TbOx)0.5(YO1.5)0.5 solid solution are prepared by the sol-gel processing and thermal vacuum evaporation onto a MgAl2O4 substrate. The temperature dependences of the electrical resistance of the films in air and CO2 are investigated. The maximum values of the relative sensitivity coefficient of the films under investigation are determined.

The enthalpies of formation of BaCe 1−xRE xO 3−δ (RE = Eu, Tb, Gd)

The preparation of BaCeO 3 doped by gadolinium, europium, and terbium oxides (BaCe 0.8Eu 0.1Tb 0.1O 2.9 and BaCe 0.8Gd 0.2O 2.9) has been performed by solid-state reaction from BaCO 3, CeO 2, Gd 2O 3, Eu 2O 3, Tb 4O 7. The X-ray measurements have showed that BaCe 0.8RE 0.2O 2.9 (RE = Gd, Eu, Tb) was orthorhombic structure (space group Pnma). The standard formation enthalpies of BaCe 0.8Eu 0.1Tb 0.1O 2.9 and BaCe 0.8Gd 0.2O 2.9 have been determined by solution calorimetry combining the solution enthalpies of BaCe 0.8Gd 0.2O 2.9 (BaCe 0.8Eu 0.1Tb 0.1O 2.9) and BaCl 2 + 0.8CeCl 3 + 0.2GdCl 3 (BaCl 2 + 0.8CeCl 3 + 0.1EuCl 3 + 0.1TbCl 3) mixtures in 1 M HCl with 0.1 M KI at T = 298.15 K and literature data.

Thermal genesis, characterization, and electrical conductivity measurements of terbium oxide catalyst obtained from terbium acetate

In this paper, the preparation and characterization of crystalline terbium oxide via thermal decomposition of acetate precursor is reported. The decomposition pathway of the parent salt was followed using TGA, DTA, and in situ electrical conductivity in air and nitrogen atmospheres. The obtained results indicated that, thermal decomposition of terbium acetate proceeded with the loss of water molecules, in two steps, below 150 °C followed by decomposition in the temperature range of 300–550 °C, throughout different intermediates, to give Tb 4O 7 as a final product. The calcination products, obtained by heating the parent salt for 3 h in air at various temperatures, were characterized using IR, XRD, SEM, nitrogen adsorption, and electrical conductivity measurements. It was demonstrated that Tb 4O 7 represents the major phase for the samples calcined at 600–900 °C. The role of Tb 3+–Tb 4+ redox couple in enhancing the electrical conductivity of the calcination products was also discussed.

Physicochemical Characteristics and Catalytic Activity of Alumina-Supported Nanosized Ceria−Terbia Solid Solutions

Alumina-supported ceria−terbia solid solution (CeO2−TbO2/Al2O3 = 80:20:100 mol % based on oxides) has been synthesized and analyzed by means of different complementary techniques, namely, X-ray diffraction (XRD), Raman spectroscopy (RS), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), ion scattering spectroscopy (ISS), temperature programmed reduction/oxidation (TPR−TPO), UV−vis diffuse reflectance spectroscopy (UV−vis DRS), BET surface area, and thermogravimetry (TG−DTA). The primary purpose of this investigation was to understand the structural and catalytic properties of ceria−terbia solid solutions dispersed over alumina support and their thermal stability. XRD studies revealed formation of ceria−terbia solid solutions without phase segregation up to the investigated temperature range of 1073 K. No specific inactive compounds were formed between the alumina support and cerium or terbium oxides. As revealed by TEM, the sizes of the Ce−Tb oxide are in the nanometer range ...

Novel varistor material based on terbium oxide

A new varistor system based on terbium oxide is introduced in this paper. The ceramic samples were prepared using the standard ceramic method and sintered in air at 1300 °C for 2 h. From the I–V measurements, the samples exhibit varistor action with the nonlinear coefficient α = 3.9 and the breakdown voltage Eb = 40 V mm−1 and possess excellent electrical stability up to 70 °C. X-ray diffraction reveals that the ceramic is a single phase structure. It is proposed that the varistor action can be attributed to the adsorbed oxygen on the grain surfaces. This is on the basis of the barrier formation model for metal oxide varistor systems and the intrinsic characteristics of terbium oxide ceramic.

Molecular layering method used to sensitize luminescence from terbium(III) Oxide nanoparticles in porous glass

Possibility of obtaining nanoparticles of terbium(III) oxide in a porous glass by impregnating the support with an aqueous solution of TbCl3 and subsequently calcining dried samples in air at 300°C was studied. The molecular layering method was used to modify the surface of encapsulated particles with titanium oxide layers of controlled thickness.

Synthesis and electrical conductivity of films based on rare-earth oxides

A number of physicochemical properties of samples are investigated. Changes in the electrical resistance of films based on the yttrium, terbium, and praseodymium oxides in an air atmosphere and upon interaction with different gaseous media (ozone, argon, methanol, ethanol) are studied. The ranges of operating temperatures and the maximum relative sensitivity coefficients of the films under investigation are determined.

Electrochemical Single-Crystal Growth of Nonstoichiometric Terbium Oxide

Single crystals of some nonstoichiometric terbium oxide phases such as Tb16O30 (TbO1.875; π-phase), Tb24O44 (TbO1.833; β2-phase), and Tb11O20 (TbO1.818; δ-phase) were artificially grown by dc electrolysis of a Tb3+ ion conducting Tb2(MoO4)3 solid electrolyte. Selective growth of a specific phase has been realized by controlling the oxygen partial pressure, the electrolysis temperature, and the voltage applied during the electrolysis. The formation of high-quality single crystals has been evidenced by the selected-area electron diffraction analysis. These nonstoichiometric phases of fluorite-related rare earth oxides have been difficult to grow in a single crystal form because they are usually obtained as mixtures of some RnO2n−2m (n = 7, 9, 11, 12, 16, 19, 24, 29, 39, 40, 48, 62, and 88; m = 1, 2, 3, 4, 6, and 8) phases. However, our dc electrolysis method can be simply applied to grow a specific nonstoichiometric phase in a single crystal form selectively at moderate temperatures at 800 or 900 °C, which had been unrealistic by the conventional growth processes via solidification of the melt at high temperatures above 2300 °C.

Fabrication of cerium active terbium aluminum garnet (TAG:Ce) phosphor powder via the solid-state reaction method

A modified solid-state reaction method for the formation of terbium aluminum garnet (TAG:Ce) powder was studied. The starting materials, which included terbium oxide (Tb 4O 7), boehmite and cerium chloride (CeCl 3·7H 2O), were pre-aged at pH 3. This pre-aging process helps to form the core–shell structure, which leads to the formation of TAG:Ce phosphor powder via a solid-state reaction more easily. The emission intensity at 551 nm of the product pre-aged at pH 3 is higher than that formed without pre-aging.

Electrochemical single crystal growth of Tb11O20

Single crystals of non-stoichiometric terbium oxide δ-Tb 11 O 20 (TbO 1.818 ) were successfully grown by direct current (dc) electrolysis of a Tb 3+ ion conducting Tb 2 (MoO 4 ) 3 solid electrolyte at 3 V and 900 °C under a low oxygen partial pressure, P O 2 = 1 × 10 −5 MPa. Selected-area electron diffraction patterns for the particles prepared by the electrolysis corresponded to that of δ-Tb 11 O 20 (TbO 1.818 ). Tb 11 O 20 forms triclinic crystals in the space group P 1 ¯ with a = 6.51 Å, b = 9.83 Å, c = 6.49 Å, α = 90.02°, β = 99.97°, and γ = 95.88°. The crystal size can be intentionally controlled by adjusting the electrolysis period. The average particle sizes were 0.69 and 1.70 μm for a week and 3 weeks electrolysis, respectively.

Luminescent glass as a promising material for x-ray conversion in radiation introscopes

Terbium oxide activated Li2O-BaO-SiO2 and Al2O3-B2O3-SiO2 glasses have been developed. These glasses have a relatively high light output and can be used for x-ray conversion in radiation introscopes. A method for measuring the brightness of x-ray luminescence converters using the equipment base of radiation introscopes has been developed.

Non-Collinear Magnetic Structure of TbB4

Non-Collinear Magnetic Structure of TbB₄

Microstructure and non-ohmic properties of ZPCCT-based ceramics

Zinc oxide doped with several different metal oxides are smart ceramic semiconductors possessing nonohmic properties, which exhibit abruptly increasing current in accordance with increasing voltage. This non-ohmicity of current–voltage properties is because of the presence of a double Schottky barrier (DSB) formed at active grain boundaries containing many trap states. Owing to highly non-ohmicity, these ceramic devices are used widely in the field of overvoltage protection systems from electronic circuits to electric power systems [1, 2]. ZnO non-ohmic ceramics are generally divided into two categories, called Bi2O3-based and Pr6O11-based ceramics, in terms of non-ohmicity-forming oxides. ZnO–Bi2O3based ceramics have been mainly studied in various aspects since ZnO non-ohmic ceramics were discovered. Although ZnO–Bi2O3-based ceramics show excellent non-ohmic properties, Bi2O3 reacts easily with some or many, but not all, of the metals used in preparing multilayer chip non-ohmic ceramics, and it destroys the multilayer structure [3]. And it is reported to have an additional insulating spinel phase, which does not play any role in electrical conduction [3]. Recently, ZnO Pr6O11-based ceramics have been studied in order to improve a few drawbacks [3] associated with Bi2O3 [4–12]. Nahm et al. reported that Zn–Pr–Co–Cr–R oxide (R = Er, Y, Dy, La)-based ceramics have highly non-ohmic properties [6, 8, 11, 12]. To develop the non-ohmic ceramics of high performance, it is very important to comprehend the effects of the additives on non-ohmic properties. No study of the effects of Tb4O7 (terbium oxide) on the non-ohmic properties has been reported. In the present study, the effect of Tb4O7 on the microstructure and non-ohmic properties of ZPCCT (ZnO–Pr6O11–CoO–Cr2O3–Tb4O7)-based ceramics was examined. Reagent-grade raw materials were prepared for ZnO non-ohmic ceramics with composition expression, such as (98.0-x) mol% ZnO + 0.5 mol% Pr6O11 + 1.0 mol% CoO + 0.5 mol% Cr2O3 + x mol% Tb4O7 (x = 0.0, 0.25, 0.5, 0.75, 1.0). Raw materials were mixed by ball milling with zirconia balls and acetone in a polypropylene bottle for 24 h. The mixture was calcined in air at 750 C for 2 h. The powder was pressed into discs of 10 mm diameter and 2 mm thickness at a pressure of 80 MPa. The discs were sintered at 1350 C for 1 h. The final samples were 8 mm in diameter and 1.0mm in thickness. Silver paste was coated on both faces of samples and the electrode was formed by heating at 600 C for 10 min. The area of electrodes was approximately 0.196 cm. The surface microstructure was examined by scanning electron microscopy (SEM, Model S2400, Hitachi, Japan). The average grain size (d) was determined by the lineal intercept method [13]. The compositional analysis of the selected areas was determined by an attached energy dispersion X-ray analysis (EDX) system. The crystalline phases were identified by powder X-ray diffraction (XRD, Model D/max 2100, Rigaku, Japan) with CuKa radiation. The sintered density (q) was measured by the Archimedes method. The current– voltage (I–V) characteristics of ZPCCT-based ceramics C.-W. Nahm (&) Department of Electrical Engineering, Dongeui University, Busan 614-714, Korea e-mail: cwnahm@deu.ac.kr J Mater Sci (2006) 41:8382–8385 DOI 10.1007/s10853-006-0775-3

PH Effects on Formation of Cerium-Doped Terbium Aluminum Garnet ( Tb2.95Al5O12 : Ce0.05 ) Phosphor Powder

Terbium aluminum garnet (TAG) was successfully synthesized by a solid-state reaction method in this study. Before calcining, the mixing powder of terbium oxide , boehmite , and cerium chloride was aged at pH 1, 2, and 3, respectively. Experimental results revealed that the better process for the formation of TAG powder was aged at pH 1. The effects of pH on the formation of TAG powder were further studied. The diffusion distance between terbium oxide and boehmite was reduced by aging the mixed slurry at pH 1. A pure phase of TAG powder was obtained after the aged mixture of boehmite, terbium oxide, and cerium chloride was heated at for and then calcined at for . The particle size of pure TAG powders is the agglomerate morphology through scanning electron microscopy observation. The formed TAG powder in this work had a maximum emission peak in as exciting at .

Electrochemical Single Crystal Growth of Tb24O44 Microparticles.

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A direct electrochemical route from oxide precursors to the terbium–nickel intermetallic compound TbNi 5

Successful direct electrochemical reduction of mixed powders of terbium oxide (Tb 4O 7) and nickel oxide (NiO) to the intermetallic compound, TbNi 5, is demonstrated in molten CaCl 2 at 850 °C by constant voltage (2.4–3.2 V) electrolysis. The reduction mechanism was investigated by cyclic voltammetry using a molybdenum cavity electrode in conjunction with characterisations of the products from both constant voltage and potentiostatic electrolysis under different conditions by XRD, SEM and EDX. It was found that the reduction started from NiO to Ni, followed by that of Tb 2O 3 (resulting from Tb 4O 7 decomposition) on the pre-formed Ni to form the intermetallic compound. The reduction speed increased with increasing the cell voltage, but the speed gain was counterbalanced by decreased current efficiency and increased electric energy consumption. At 2.4 V, the current efficiency reached 63.2%, and the energy consumption by electrolysis was as low as 3.2 kWh/kg TbNi 5 when the oxide phase was converted fully to the metal phase (XRD) in 4 h. The oxygen level in the produced TbNi 5 could readily reach 1800 ppm by electrolysis at 3.2 V for 12 h with the energy consumption being 18.9 kWh/kg TbNi 5.

Electrochemical Metallization of Solid Terbium Oxide

From solid to solid: Electrochemical conversion of solid terbium oxide into solid terbium metal was performed in molten CaCl2 under the conditions for Ca deposition. Electron transfer to the solid oxide was more effective from the electrode than from the deposited Ca, and the process was controlled by mass transfer in the porous oxide electrode.

Electrochemical single crystal growth of Tb 24O 44 microparticles

Single crystals of non-stoichiometric terbium oxide Tb 24O 44 (≡TbO 1.833) were successfully grown by the dc electrolysis of the Tb 3+ ion conducting Tb 2(MoO 4) 3 solid electrolyte at the moderate conditions of 3 V at 900 °C. Electron diffraction patterns for each particle grown clearly indicate that the particles were single crystals of the β2-phase of high quality Tb 24O 44 (≡TbO 1.833). Tb 24O 44 is triclinic of space group P 1 ¯ with a = 6.49 Å, b = 12.27 Å, c = 12.43 Å, α = 78.51°, β = 99.82° and γ = 71.12°. The crystal size can be intentionally controlled by adjusting the electrolysis period: the average particle sizes were 0.40, 0.65 and 1.52 μm for 1, 2 and 4 weeks electrolysis, respectively.

Anomalous Tb3+ luminous spectrum in the TiO2 nanocrystals

In order to get Tb 3+ luminescence in the TiO 2 nanocrystals, nanoaggregate of terbium oxide in the TiO 2 nanocrystal has been produced using a reverse micelles and solvothermal method in toluene solution. Transmission electron microscopy and X-ray diffraction measurements have identified particles with average size of 6.7–10.2 nm in the anatase phase corresponding to the sintering temperature. The time-resolved spectroscopic technique has been used for the measurement of luminescence spectra and decay curves. No emission from Tb 3+ ions was observed from the sample with Tb 3+ ions dispersed in TiO 2 . However, from the sample that terbium oxide is formed a colony of aggregates in the TiO 2 solution strong emissions from 5 D 4 levels of Tb 3+ ions were observed. The PL spectrum was very anomalous, extraordinarily it has a very strong emission band due to the transition of 5 D 4 → 7 F 2 . It was proposed to describe anomalous spectrum that two kinds of energy migrations ( 5 D 4 – 7 F 6 and 5 D 4 – 7 F 2 ) are occurred among Tb 3+ ions, and quenching centers located at the boundary of titanium oxide powerfully operate to higher energy.