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31. Revealing the influence of Nb-doping on the crystal structure and electromechanical properties of (K, Bi)(Mg, Ti, Nb)O3 ceramics.

Author

Zeb, Aurang, Akram, Fazli, Habib, Muhammad, Iqbal, Qamar, Ullah, Amir, Ullah, Ihsan, Ali, Nasir, Milne, S. J., Sheeraz, Muhammad, Ingram, Conrad, Iqbal, Shahid, Hussain, Fayaz, Younis, Adnan, Tho, P. T., and Ahn, Chang Won

Abstract

Nb-modified lead-free ceramics (K0.48Bi0.52)(Mg0.02Ti0.98−xNbx)O3, (KBT-BMTNbx with x = 0.00 − 0.05) were synthesized by a conventional solid-state reaction route followed by furnace cooling. The effects of Nb-doping on the structural properties and electrical properties of KBT-BMTNbx ceramics have been investigated. The X-ray diffraction pattern indicates a mixed tetragonal and cubic phase for the pure KBT-BMTNbx ceramics. Therefore, a large piezoelectric actuator coefficient d33* ≈ 700 pm/V, piezoelectric sensor coefficient (d33 ≈ 133 pC/N) along with remnant polarization (Pr ≈ 17.5 µC/cm2), maximum electromechanical strain ≈ 0.35% and maximum temperature (Tm ≈ 336 ºC) were obtained for KBT-BMTNbx. However, with Nb-doping, a compositionally driven phase transformation occurred from mixed rhombohedral and tetragonal phases to cubic phase. Because of the excess Nb-doping in the KBT-BMT ceramics, the grain size suddenly decreased, as a result, the long-range ferroelectric phase was converted into a short-range relaxor phase. Hence, a low dielectric loss tanδ ≈ 0.02 was achieved at x = 0.02 composition. This superior dielectric performance is correlated to the crystal structure morphotropic phase boundary, optimum grain size (≈ 2 μm), maximum lattice distortion, and soft-ferroelectric effect induced by the donor doping. The main aim of recent research is to investigate Pr, d33, d33*, Smax, and reduced tanδ for practical applications in the real world. [ABSTRACT FROM AUTHOR]

Published
2023
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34. Job Stress And Turnover Intentions Among School Teachers Of Punjab Pakistan

Author

Khalid Mahmood, Abdul Ghaffar, M. Irshad Ullah, Amir Zaman

Subjects
Job Stress, Turnover Intentions, Descriptive Statistics, Inferential Statistics
Abstract

Job Stress is considered as a stimulator of turnover intentions among the employees of any organization. As the teachers belong to a noble profession i.e. profession of the Prophets, hence the researcher, in order to verify this supposition, conducted this descriptive, co-relational and cross-sectional study for determining the relationship between job stress and turnover intentions among different categories of teachers working in public sector schools of Punjab Pakistan. Due to shortage of time and financial resources, this study was delimited to Faisalabad Division. The sample of this study comprised 700 respondents selected by multi-stage proportionate stratified random sampling technique. Standardized scales were employed for determining the workplace stress and turnover intentions after taking permissions. In addition to descriptive statistics, inferential statistics i.e. Independent Sample t-test, One Way ANOVA, Pearson Correlations Co-efficient and Linear Regression were also calculated from the collected data using SPSS 23 with the aim to test the already formulated null hypotheses of the study. Based on the study findings, it was concluded thatthere is moderate level positive correlation between teachers’job stress and theirturnover intentions as well asjob stress is a significant predictor of teachers’ turnover intentions.

Published
2022
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43. Enhancement of dielectric and energy density properties in the PVDF-based copolymer/terpolymer blends

Author

Ullah, Amir, Rahman, Ata ur, Ahn, Chang Won, Rahman, Muneeb-ur, Ullah, Aman, Rehman, Zia-ur, Iqbal, Muhammad Javid, and Kim, III Won

Subjects
Dielectric materials -- Electric properties -- Properties, Polyvinylidene fluoride -- Electric properties, Conducting polymers -- Properties, Engineering and manufacturing industries, Science and technology
Abstract

We investigated the high dielectric constant and energy storage density for the blends of P(VDF-TrFE) copolymer and P(VDF-TrFE-CFE) terpolymer. The degradation of coercive field ([E.sub.c]) and remnant polarization ([P.sub.r]) of the copolymer under an electric field of 125 MV/m was observed and the copolymer changed into a typical relaxor ferroelectric with doping of terpolymer. The dielectric constant of P(VDF-TrFE) was found to be ~11, but was enhanced to ~55 by blending with P(VDF-TrFE-CFE) at 60 wt%. Consequently, a higher energy density of about 4.2 J/[cm.sup.3] was obtained in these blends in contrast to about 3.6 J/[cm.sup.3] in the terpolymer at the very low applied electric field of 125 MV/m. These results demonstrate the promise of blend approaches for tailoring and enhancing the dielectric properties of ferroelectric polymers., INTRODUCTION Poly(vinylidene difluoride) (PVDF)-based polymers have attracted much attention due to their multifunctional electroactive polymers with superior mechanical properties. Their potential to be used as high permittivity dielectrics [1-6], organic [...]

Published
2015
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48. High Strain Response and Dielectric Properties of Bi1/2(Na0.78K0.22)1/2TiO3 Ceramics Doped with (Fe1/2Nb1/2)4+.

Author

Naz, Saima, Ullah, Amir, Zeb, Aurang, Akram, Fazli, Karoui, Abdennaceur, Sheeraz, Muhammad, and Ahn, Chang Won

Subjects
DIELECTRIC properties, PIEZOELECTRIC actuators, PERMITTIVITY, CERAMICS, GRAIN size, LEAD titanate
Abstract

Environmentally friendly piezoceramics Bi1/2(Na0.78K0.22)1/2Ti1-x(Fe1/2Nb1/2)xO3 (BNKT-FN) with FeNb (FN) ratios 0, 0.01, 0.02, 0.03 and 0.04 were synthesized via conventional solid-state reaction (CSSR). X-ray diffraction (XRD) analysis revealed that the FN complexes were completely dissolved in BNKT perovskite and the structural transition occurred from ferroelectric to relaxor state. The average grain sizes for x = 0, 0.01, 0.02, 0.03 and 0.04 were found to be 0.34 μm, 0.35 μm, 0.38 μm, 0.32 μm and 0.39 μm, respectively. It is observed that the grain size increased with the addition of FN, except for x = 0.03. The coercive field (Ec) and remnant polarization (Pr) of the system were decreased with increasing FN concentration and the highest Ec of 21.1 kV/cm and Pr of 29.2 μC/cm2 were noted for the base pure sample. In addition, the increase of FN content steadily broadened the dielectric anomaly at maximum dielectric constant temperature (Tm) in the BNKT-FN system. Consequently, unipolar normalized strain (Smax/Emax) was found to be enhanced monotonically achieving the highest value of around 654 pm/V (x = 0.02). These properties suggest that the investigated system could be a promising eco-friendly candidate for piezoelectric actuators and many other applications requiring high piezoelectric induced strain. [ABSTRACT FROM AUTHOR]

Published
2022
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49. Extracellular Vesicles Derived From Talaromyces marneffei Yeasts Mediate Inflammatory Response in Macrophage Cells by Bioactive Protein Components

Author

Yang, Biao, primary, Wang, Jingyu, additional, Jiang, Hongye, additional, Lin, Huixian, additional, Ou, Zihao, additional, Ullah, Amir, additional, Hua, Yuneng, additional, Chen, Juanjiang, additional, Lin, Xiaomin, additional, Hu, Xiumei, additional, Zheng, Lei, additional, and Wang, Qian, additional

Published
2021
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