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Subsolidus solution and ionic conductivity of rock-salt structured Li3+5xTa1−xO4 electroceramics

Shari S., Tan K. B., Khaw C. C., Zainal Z., Lee O. J., Chen S. K.

Materials Science Poland

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2020

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Vol. 38, No. 3

465--474

EN

Lithium tantalate solid solution, Li3+5xTa1−xO4 was prepared by conventional solid-state reaction at 925 °C for 48 h. The XRD analysis confirmed that these materials crystallized in a monoclinic symmetry, space group C2/C and Z = 8, which was similar to the reported International Crystal Database (ICDD), No. 98-006-7675. The host structure, β-Li3TaO4 had a rock-salt structure with a cationic order of Li+:Ta5+ = 3:1 over the octahedral sites. A rather narrow subsolidus solution range, i.e. Li3+5xTa1−xO4 (0 ⩽ x ⩽ 0.059) was determined and the formation mechanism was proposed as a replacement of Ta5+ by excessive Li+, i.e. Ta5+ ↔ 5Li+. Both Scherrer and Williamson-Hall (W-H) methods indicated the average crystallite sizes in the range of 31 nm to 51 nm. Two secondary phases, Li4TaO4.5 and LiTaO3 were observed at x = 0.070 and x = −0:013, respectively. These materials were moderate lithium ionic conductors with the highest conductivity of ~2.5 × 10-3 Ω -1∙cm-1 at x = 0, at 0 °C and 850 °C; the activation energies were found in the range of 0.63 eV to 0.68 eV.

2

High temperature impedance spectroscopy study of non-stoichiometric bismuth zinc niobate pyrochlore

Tan K. B., Khaw C. C., Lee C. K., Zainal Z., Tan Y. P., Shaari H.

Materials Science Poland

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2009

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Vol. 27, No. 3

825--837

EN

Single phase non-stoichiometric bismuth zinc niobate, Bi3Zn1.84Nb3O13.84, was fabricated by a conventional solid state method. The sample was refined and fully indexed on the cubic system, space group Fd3m (No. 227), Z = 4 with A = 10.5579(4) A. Electrical characterisation was performed using an ac impedance analyser over the temperature range of 25-850 °C and frequency range of 5 Hz-13 MHz. Typical dielectric response is observed in Bi3Zn1.84Nb3O13.84 with a high relative permittivity, low dielectric loss and a negative temperature coefficient of capacitance, with the values of 147, 0.002 and -396 ppm/°C, at 100 kHz at ambient temperature, respectively. This material is highly resistive, with a conductivity of 1×10-21 A-1 Acm-1 and a high activation energy of ca. 1.59 eV.

3

High temperature impedance spectroscopy study of non-stoichiometric bismuth zinc niobate pyrochlore

Tan K. B., Khaw C. C., Lee C. K., Zainal Z., Tan Y. P., Shaari H.

Materials Science Poland

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2009

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Vol. 27, No. 4/1

947--959

EN

Single phase non-stoichiometric bismuth zinc niobate, Bi3Zn1.84Nb3O13.84 was prepared by a conventional solid state method. The sample was refined and fully indexed on the cubic system, space group Fd3m, Z = 4 with a = 10.5579(4) A. Electrical characterisation was performed using an ac impedance analyser over the temperature range of 25-850 °C and frequency range of 5 Hz - 3 MHz. Typical dielectric response was observed in Bi3Zn1.84Nb3O13.84with high relative permittivity, low dielectric loss and negative temperature coefficient of capacitance, with the values of 147, 0.002 and -396 ppm/°C, at 100 kHz at ambient temperature, respectively. The material is highly resistive, with the conductivity of 10-21 ohm-1ocm-1 and a high activation energy of 1.59 eV.

4

Photoelectrochemical properties of sol-gel derived TiO2 thin films in aqueous sodium oxalate solution

Zainal Z., Lee C. Y., Hussein M. Z., Kassim A.

Materials Science Poland

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2004

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Vol. 22, No. 2

99--110

EN

Photoelectrooxidation of aqueous sodium oxalate on TiO2 thin films has been investigated. The films, prepared by sol-gel dip-coating, were characterised using Scanning Electron Microscopy and X-ray Diffractometry. Photosensitivity of samples was studied using Linear Sweep Voltammetry and Chronoamperometry techniques. The photoelectrochemical performance of thin film electrodes was evaluated in function of heat treatment, number of dip-coatings and applied potential. The percentage of oxalate degradation was determined by calculating the total charge from the photocurrent. The films heat-treated at 773 K were better fitted to indirect optical transition with Eg = 3.21 eV.

5

Pamoate intercalated Zn-Al layered double hydroxide for the formation of layered organic-inorganic intercalate

Hussein M. Z., Jubri Z. B., Zainal Z., Yahya A. H.

Materials Science Poland

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2004

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Vol. 22, No. 1

57--67

EN

A layered organic-inorganic intercalate was prepared by the self-assembly technique using pamoate (PA) as an organic guest in the Zn-Al layered double hydroxide inorganic host (ZAPAN). Various concentrations of PA, ranging from 0.01 to 0.04 M, were used to prepare the intercalated compound with a constant 4:1 ratio of Zn:Al in the mother liquor. The concentration of PA of 0.02 M at pH 7 was found to give a well-ordered nanolayered organic-inorganic hybrid structure. As a result of successful intercalation of PA anion into the Zn-Al inorganic layered double hydroxide (LDH), the expansion of interlayer spacing to 18 A was observed in the PXRD diffractogram of the intercalated compound, compared to 9 A for the Zn-Al LDH with nitrate as the counter anion (ZANIL). FTIR study shows that the intercalated compound resembled the spectra of PA and ZANIL, thus indicating the presence of both functional groups in ZAPAN. It was also found that the BET surface area increased from 6 m2/g to 90 m2/g for ZANIL and ZAPAN, respectively. The pore texture of the resulting materials was also changed as the result of the intercalation and the expansion of the basal spacing together with pore formation between the crystallite during the formation of the resulting layered intercalated compound.

6

Tin selenide thin films prepared through combination of chemical precipitation and vacuum evaporation technique

Zainal Z., Nagalingam S., Kassim A., Hussein M. Z., Yunus W. M. M.

Materials Science

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2003

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Vol. 21, No. 2

225-233

EN

Tin selenide thin films were prepared through combination of chemical precipitation and vacuum evaporation technique. The vacuum deposition was carried out at different quantity of the starting material. The difference in the structural and compositional properties of the deposited films were studied. The films were characterised using various techniques such as x-ray diffractometry, scanning electron microscope and energy dispersive analysis of x-ray. Photoactivity of the samples was studied using linear sweep voltammetry. The films were found to be p-type semiconductors. The optical bandgap energy was found to be indirect and equal to Eg = 1.25 eV.