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- 저자 : Yaseen Iqbal (검색결과 3 건)
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Low Loss La5-xSrxTi4+xAl1-xO17 Ceramics for Microwave Dielectric Applications
Yaseen Iqbal,Raz Muhammad 대한금속·재료학회 2015 ELECTRONIC MATERIALS LETTERS Vol.11 No.3
La5-xSrxTi4+xAl1-xO17 (x = 0, 0.20, 0.25 and 0.30) ceramics were prepared through a mixed oxide solid state sintering route and characterized in terms of phase, crystal structure, microstructure and microwave dielectric properties. La5Ti4AlO17 exhibited reasonable relative permittivity εr ~ 42, a high quality factor Q×fo ~ 18906 GHz but the temperature coefficient of resonance frequency τf ~ −19 ppm/°C was too low for practical applications. In order to tune τf through zero, Sr was substituted for La which increased εr to 47.1, decreased Q×fo to 16678 GHz and decreased negative τf to −4.8 ppm/°C at x = 0.25. The observed decrease in negative τf may be due an increase in tolerance factor and hence change in tilt scheme of BO6 octahedra as a result of substitution of larger cations for smaller cations.
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Phase evolution and microstructure-property relationship in red clay bricks
Safeer Ahmad,Yaseen Iqbal 한양대학교 세라믹연구소 2016 Journal of Ceramic Processing Research Vol.17 No.4
Clay brick is one of the oldest and commonly used clay products in construction industry in Khyber Pakhtunkhwa (KP)Pakistan. In spite of its widespread use, studies regarding the manufacturing standards and quality of locally made bricks aremuch less in comparison to those of technologically advanced countries. The aim of the present study was to investigate thechemistry and phase constitution of the raw materials used in local brick kilns. Phase and microstructural analyses of firedbricks from local kilns were performed and compared with those of the laboratory made bricks. X-ray diffraction of rawmaterials revealed the presence of illite, quartz, clinochlore and albite while calcite was identified as a minor phase in all theinvestigated samples. Diopside, anorthite and quartz were observed as major phases in the kiln-fired samples, and onlydiopside and quartz in the laboratory-fired samples. The presence of albite and clinochlore, although in small concentrations,in the kiln-fired samples indicated that the employed temperature was too low to completely dissolve the initial ingredients. Consistent with X-ray diffraction results, semi-quantitative energy dispersive spectroscopy revealed the presence of silicon,aluminum, calcium, magnesium, iron and potassium along with a small amount of sodium in these samples. An increase infiring temperature decreased porosity which resulted in substantial increase in compressive strength and decrease in waterabsorption. The optimum mechanical properties were achieved at 1000 oC.
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Advances in stable and flexible perovskite solar cells
Qamar Wali,Faiza Jan Iftikhar,Naveen Kumar Elumalai,Yaseen Iqbal,Sidra Yousaf,Shahid Iqbal,Rajan Jose 한국물리학회 2020 Current Applied Physics Vol.20 No.5
Roll-to-roll (R2R) production is an innovative approach and is fast becoming a very popular industrial method for high throughput and mass production of solar cells. Replacement of costly indium tin oxide (ITO), which conventionally has served as the transparent electrode would be a great approach for roll to roll production of flexible cost effective solar cells. Indium tin oxide (ITO) and fluorine-doped tin oxide (FTO) are brittle and ultimately limit the device flexibility. Perovskite solar cells (PSCs) have been the centre of photovoltaic research community during the recent years owing to its exceptional performance and economical prices. The best reported PSCs fabricated by employing mesoporous TiO2 layers require elevated temperatures in the range of 400–500 °C which limits its applications to solely glass substrates. In such a scenario developing flexible PSCs technology can be considered a suitable and exciting arena from the application point of view, them being flexible, lightweight, portable, and easy to integrate over both small, large and curved surfaces.
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