Orhan Turkoglu

Synthesis and characterization of β type solid solution in the binary system of Bi2O3-Eu2O3

We have investigated Bi2O3-Eu2O3 binary system by doping with Eu2O3 in the composition range from 1 to 10 mole% via solid state reactions and succeeded to stabilize β-Bi2O3 phase which is metastable when pure. Stability of β-Bi2O3 polymorph was influenced by heat treatment temperature. Tetragonal type solid solution was obtained in 3–6 mole% addition range when annealed at 750°C and the range was 2–7 mole% when annealed at 800°C. We have also carried out investigations on lattice parameters, microstructural properties and elemental compositions of this β type solid solution for each doping ratio. Lattice parameters increased with amount of Eu2O3 addition. Our experimental observations strongly suggested that oxygen deficiency type non-stoichiometry is present in doped β type solid solutions.

Electrical conductivity of g-Bi2O3-V2O5 solid solution

The total conductivity (σT) in bcc γ-Bi2O3 doped with V2O5 system has been measured in the composition range between 1 and 7 mol% V2O5 at different temperatures. Phase transitions for different addition amounts depending on the temperature were investigated by quenching the samples. According to the XRD and DTA/TG results, this bcc type solid solution was stable up to about 720°C and the solubility limit was found at ˜7 mol% V2O5 in γ-phase. This system showed predominantly an oxide ionic conduction. As the V2O5 addition increased, the ionic conduction increased up to 5 mol% V2O5 at which the highest conductivity was found to be 8.318·10-2 Ω-1 cm-1 at 700°C and then decreased. It has been proposed that γ-Bi2O3 phase contains a large number of oxide anion vacancies and incorporated vanadium cations at tetrahedral sites which affect the oxygen sublattice of the crystal structure.

Spectrophotometric determination of samarium(III) with chrome azurol S in the presence of cetylpyridinium chloride

A sensitive, simple method for the determination of trace amounts of samarium by spectrophotometry is described based on the formation of the samarium-chrome azurol S (CAS) complex in micellar medium. The molar absorptivities of the complexes at pH 7.5 at 505 nm were 3.6x10(4) and 1.4x10(5) l mol(-1) cm(-1) for water media and cetylpyridinium chloride (CPC), respectively. Beers law is obeyed from 0.05-2 mg l(-1) of samarium at 505 nm as Sm-CAS-CPC complex. Optimal conditions such as reagent amounts, and pH for the samarium determination were reported. The effects of foreign ions were also investigated. The proposed method was successfully applied to the determination of samarium contents in synthetic samples.

Electrical conductivity of the ionic conductor tetragonal (Bi2O3)1-x(Eu2O3)x

AbstractElectrical conductivity of tetragonal β-phase (Bi 2 O 3 ) 1-x (Eu 2 O 3 ) x (0.01 ≤ x ≤ 0.10 %mol) ceramic systems were investigated. The temperature and doping concentration dependences of the electrical conductivity were studied by four-point probe technique. The electrical conductivity increases with the increasing doping concentration and temperature. The highest value of the electrical conductivity is 0.013 Ω -1 cm (x = 0.05, 750 o C) for the β-phase at 670 o C and 0.57 Ω -1 cm (x=0.05, 800 o C) in binary systems at 690 o C. The phase transition which manifests itself by the jump in the conductivity curves was seen and verified by differential thermal analysis measurements. The activation energies of the samples were found to be about 0.71-1.57 eV.Keywords: anionic conductors, bismuth oxide, ionic conductivity, four-point probe technique.ResumoFoi estudada a condutividade eletrica de sistema cerâmicos da fase β tetragonal (Bi 2 O 3 ) 1-x (Eu 2 O 3 ) x (0,01 ≤ x ≤ 0,10 mol%). A dependencia da condutividade eletrica da temperatura e da concentracao de dopantes foi estudada pela tecnica das quatro pontas de prova. A condutividade eletrica aumenta com o aumento da concentracao de dopantes e da temperatura. O maior valor da condutividade eletrica e 0,013 Ω

Synthesis,Crystal Structural and Electrical Conductivity Properties of Fe-Doped Zinc Oxide Powders at High Temperatures

The synthesis, crystal structure and electrical conductivity properties of Fe-doped ZnO powders (in the range of 0.25{15 mol%) were reported in this paper. I-phase samples, which were indexed as single phase with a hexagonal (wurtzite) structure in the Fe-doped ZnO binary system, were determined by X-ray difiraction (XRD). The solubility limit of Fe in the ZnO lattice is 3 mol% at 950 ‐ C. The above mixed phase was observed. And the impurity phase was determined as the cubic-ZnFe2O4 phase when compared with standard XRD data using the PDF program. This study focused on single I-phase ZnO samples which were synthesized at 950 ‐ C because the limit of the solubility range is the widest at this temperature. The lattice parameters a and c of the I-phase decreased with Fe-doping concentration. The morphology of the I-phase samples was analyzed with a scanning electron microscope. The grain size of the I-phase samples increased with heat treatment and doping concentration. The electrical conductivity of the pure ZnO and single I-phase samples was investigated using the four-probe dc method at 100{950 ‐ C in air atmosphere. The electrical conductivity values of pure ZnO, 0.25 and 3 mol% Fe-doped ZnO samples at 100 ‐ C were 2£10 i6 , 1.7£10 i3 and 6.3£10 i4 S¢cm i1 , and at 950 ‐ C they were 3.4, 8.5 and 4 S¢cm i1 , respectively.

Studies on structural and electrical properties of copper-doped zinc oxide powders prepared by a solid state method at high temperatures

Abstract The synthesis, crystal structure and electrical conductivity properties of Cu-doped ZnO powders (in the range of 0.25 – 15 mole %) is reported. I-phase samples, which were indexed as single phase with a hexagonal (wurtzite) structure in the Cu-doped ZnO binary system, were determined by X-ray diffraction. The limit solubility of Cu in the ZnO lattice at this temperature is 5 mole % at 1000°C. The impurity phase was determined as CuO when compared with standard XRD data using the PDF program. We focused on single I-phase ZnO samples which synthesised at 1000°C because the limit solubility range is widest at this temperature. It was observed that the lattice parameters a increased and c decreased with Cu doping concentration. The morphology of the I-phase samples was analysed with a scanning electron microscope. The electrical conductivity of the pure ZnO and single I-phase samples were studied using the four-probe dc method at temperatures between 100 and 950°C in an air atmosphere. The electrical conductivity values of pure ZnO and 5 mole % Cu-doped ZnO samples at 100°C were 2 × 10−6 and 1.4 × 10−4 ohm−1 cm−1, and at 950°C they were 1.8 and 3.4 ohm−1 cm−1, respectively. In other words, the electrical conductivity slightly increased with Cu doping concentration. Also, it was observed that the activation energy of the I-phase samples was decreased with Cu doping concentration.

Effect of Doping and High-Temperature Annealing on the Structural and Electrical Properties of Zn1–X NiXO(0≤X≤0.15) Powders

This paper reported the synthesis, crystal structure and electrical conductivity properties of Ni-doped ZnO powders (i.e. Zn1–X NiXO binary system, X =0, 0.0025, 0.005, 0.0075 and in the range 0.01≤X≤0.15). I-phase samples, which were indexed as single phase with a hexagonal (wurtzite) structure in the Zn1–X NiXO binary system, were determined by X-ray diffraction (XRD). The widest range of the I-phase was determined as 0≤X≤0.03 at 1200°C; above this range the mixed phase was observed. The impurity phase was determined as NiO when compared with standard XRD data, using the PDF program. We focused on single I-phase ZnO samples which were synthesized at 1200°C because of the widest range of solubility limit at this temperature. It was observed that the lattice parameters a and c of the I-phase decreased with Ni doping concentration. The morphology of the I-phase samples was analyzed with a scanning electron microscope. The electrical conductivity of the pure ZnO and single I-phase samples were studied by using the four-probe dc method at temperatures between 100 and 950°C in air atmosphere. The electrical conductivity values of pure ZnO and 3 mol% Ni-doped ZnO samples at 100°C were 2×10−6 and 4.8×10−6 Ω−1 cm−1, and at 950°C they were 1.8 and 3.6 Ω−1 cm−1, respectively. In other words, electrical conductivity increased with Ni doping concentration.

Oxide ionic conductivity and crystallographic properties of tetragonal type Bi2O3-based solid electrolyte doped with Ho2O3

Abstract In the present work, the authors have investigated the binary system of (Bi2O3)1–x(Ho2O3)x. For the stabilisation of the tetragonal type solid solution, small amounts of Ho2O3 were doped into the monoclinic Bi2O3 via solid state reactions in the stoichiometric range 0·01≤x≤0·1. The crystal formula of the formed solid solution was determined as Bi(III)4–4xHo(II)4xO6–2xVo(2+2x) (where Vo is the oxide ion vacancy) according to the XRD and SEM microprobe results. In the crystal formula, stoichiometric values of x were 0·04≤x≤0·08, 0·03≤x≤0·09, 0·02≤x≤0·09 and 0·04≤x≤0·09 for annealing temperatures at 750, 800, 805 (quench) and 760°C (quench) respectively. The four probe electrical conductivity measurements showed that the studied system had an oxide ionic type electrical conductivity behaviour, which is increased with increasing dopant concentration and temperature. The obtained solid electrolyte system has an oxygen non-stoichiometry characteristic, and it contains O2– vacancies, which have disordered arrangements in its tetragonal crystal structure. The increase in the amount of Ho2O3 doping and temperature causes an increasing degree of the disordering of oxygen vacancies and a decrease in the activation energy Ea.

Synthesis and characterization of γ-Bi2O3 based solid electrolyte doped with Nb2O5

Abstractγ-phase bismuth oxide is a well known high oxygen ion conductor and can be used as an electrolyte for intermediate temperature solid oxide fuel cells (IT-SOFCs). This study aims to determine new phases of Bi2O3-Nb2O5 binary system and the temperature dependence of the electrical transport properties. The reaction products obtained in open air atmosphere were characterized by X-ray powder diffractions (XRD). The unit cell parameters were defined from the indexes of the powder diffraction patterns. The γ-Bi2O3 crystal system were obtained by doping 0.01 < mole% Nb2O5 < 0.04 at 750 °C for 48 and 96 h. Thermal behaviour and thermal stability of the phases were investigated by thermal analysis techniques. Surface and grain properties of the related phases were determined by SEM analysis. The temperature dependence of the electrical properties of γ-Bi2O3 solid solution was measured by four-point probe d.c. conductivity method. In the investigated system, the highest value of conductivity was observed for σT = 0.016 ohm−1 cm−1 at 650 °C on 4 mole% Nb2O5 addition. The electrical conductivity curves of studied materials revealed regular increase with temperature in the form of the Arrhenius type conductivity behaviour.

Synthesis of β-Phase (Bi2O3)1-x (Dy2O3)x (0.01<x<0.10) System and Measurement of Oxygen Ionic Conductivity

β-phase (Bi2O3)1-x (Dy2O3)x system with tetragonal structure is synthesized for 0.01<x<0.10 molar doping. Unit cell parameters increased with increasing the doping. We have studied the dependence of total electrical conductvity on temperature, doping concentration of β-phase systems. The phase transition which manifests itself by the jump in the conductivity curve was also verified by DTA and both measurements are rather compatible. The electrical conductivity curves of β-phase structure revealed regular increase in the form of an Arrhenius curve. The activation energies are calculated from these graphs. Bi2O3-based Dy2O3 doped ceramics show ionic oxygen conductivity. The conductivity increased as the doping concentration increased. The highest value of conductivity is 0.006 0.006 ohm-1cm-1(600∘C) for the β-phase (Bi2O3)0.91 (Dy2O3)0.09(800∘C). The sample with the highest conductivity is (Bi2O3)0.91 (Dy2O3)0.09(800∘C) binary system where 1.450 ohm−1cm−1(745∘C).