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Processing and Microstructure-Property Microstructure Property Relationship of Low Temperature Environment-Friendly Environment Friendly Piezoelectric Materials

Thesis Info

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Author

Zaman, Arif

Program

PhD

Country

Pakistan

Thesis Completing Year

2006

Thesis Completion Status

Completed

Subject

Physics

Language

English

Link

http://prr.hec.gov.pk/jspui/handle/123456789/1406

Added

2021-02-17 19:49:13

Modified

2024-03-24 20:25:49

ARI ID

1676727017607

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Lead-based electro ceramics like PZT are the most commercially used as sensors, actuators and transducers due to their excellent electromechanical response, however The environmental concerns and the legislation imposed on hazardous materials, lead is considered toxic and its use is banned for many applications. Therefore the alternative lead free electroceramics have become the focus of research in both industry and academia. In our present work among the several families of lead-free, we will focus on the bismuth-based ferroelectric ceramics due to their excellent piezoelectric and ferroelectric properties. In brief this thesis we will emphasize on the improvement of ferroelectric and field-induced strain properties of BNKT-LS ceramic system by different alovilent and isovalent B-site substitutions. The effect of zirconium (Zr+4), niobium (Nb+5) and tantalum (Ta+5) substitution for the B-site in the host perovskite unit cell on the dielectric, electromechanical and piezoelectric properties of lead-free 0.99[Bi1/2(Na0.82K0.18)1/2TiO3]-0.01LiSbO3 (BNKT-LS) piezoceramics has been investigated. The ternary BNKT-LS system was synthesized using low temperature conventional solid state reaction method. Crystal structure, dielectric, ferroelectric and field-induced strain behavior of Zr modified lead-free 0.99[Bi1/2(Na0.82K0.18)1/2(Ti1-xZrx) O3]-0.01LiSbO3 (BNKTZ-LS) ceramics were investigated in composition range x = 0 - 0.040. XRD patterns revealed the formation of pure perovskite phase with no apparent structural phase transition with pseudo cubic symmetry for the compositions at low concentration of dopants although there were some traces of secondary phases at higher concentrations. The temperature-dependent dielectric peaks of the BNKTZ-LS ceramics broadened and ferroelectric polarizations decreased with increasing Zr concentration. Ferroelectric and bipolar field induced-strain curves indicated a disruption of ferroelectric order upon Zr addition into BNKT-LS ceramics. This destabilization of the ferroelectric order was accompanied by an enhanced field-induced strain. A high field-induced strain (S = 0.30%) with a normalized strain (d*33 = Smax/Emax = 500 pm/V) was observed at an applied electric field of 6 kV/mm at x = 0.020. The Ta-modified 0.99[(Bi0.82Na18)TiO3-(Bi1/2K1/2)TiO3]- 0.01LiSbO3 (BNKTT-LS) piezoceramics were also synthesized by a conventional solid-state reaction method. The effect of Ta addition into the BNKT-LS ceramics were studied through X-ray diffraction, dielectric, temperature dependent ferroelectric and field-induced strain characterizations. As the Ta content was increased, the maximum dielectric constant as well as the depolarization temperature (Td) decreased. The polarization and strain hysteresis loops indicate that the addition of Ta significantly disrupts the ferroelectric order of the BNKT-LS ceramics leading to a degradation of the remnant 14 polarization and coercive field. However, the destabilization of the ferroelectric order is accompanied by a significant enhancement in the unipolar strain. A large unipolar field-induced strain of 0.38% with a normalized (d*33 = Smax/Emax = 650 pm/V) at a driving field of 6 kV/mm was obtained at room temperature for x = 0.013. This significant strain enhancement is a result of the reversible phase transition between a NP phase in a zero field and a field-induced ferroelectric phase. Finally the effect of Nb-substitution on the dielectric, electromechanical and piezoelectric properties of Pb-free 0.99[Bi1/2(Na0.82K0.18)1/2Ti1-xNbxO3]-0.01LiSbO3 (BNKT-LS) piezoelectric ceramics has been investigated. X- ray diffraction analysis reveals pseudo-cubic symmetry for the compositions with x = 0 - 0.030. Both the dielectric constant εr and depolarization temperature Td decreased with an increase in Nb content. An analysis of the electric field induced polarization and strain hysteresis loops indicated that Nb substitution disrupted the long range ferroelectric order of BNKT-LS ceramics. This degraded the remnant polarization, coercive field and piezoelectric coefficient d33 while the electric field induced strain increased (peaked at x=0.015) to 0.43% corresponding to a normalized strain (d33* = 614 pm/V) at a deriving field of 7 kV/mm. This abnormal strain enhancement may be attributed to the reversible phase transition between the polar and non-polar phases. At high Nb concentrations, BNKNb-LS ceramics shows a typical relaxor behavior. So for all dopants the increase in concentration results in a decrease in the maximum dielectric constant as well as the depolarization temperature Td, the disruption of the long range ferroelectric order, the degradation of remnant polarization, coercive field and piezoelectric coefficient d33. This was also accompanied by enhancement in the electric field induced strain. This abnormal strain enhancement could be attributed to a reversible phase transition between polar and non-polar phase for all systems. For high doping level BNKT-LS ceramics showed a typical relaxor behaviour.
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3۔اندھا بوڑھا

اندھا بوڑھا

نعمان نذیر

صبح ہوتے ہی  معمول سے کچھ دیر پہلے ہی اس کی آ نکھ کھل گئی ۔ یوں تو وہ آ غاز سے ہی اپنے کام میں مہارت کے ساتھ ساتھ وقت کی پابندی کا بھی قائل تھا۔ شاید ہی ان دس سالوں میں کھبی اس کو افسران بالا کی طرف سے اس بات کا اعتراض کیا گیا ہو کہ وہ وقت پہ دفتر نہیں پہنچا ۔ ان دس سالوں میں اس کے افسر جو متعدد تبدیل ہو چکے تھے۔ کوئی بھی اس کے کام پہ معترض نہ تھا۔۔۔۔۔۔۔

آج اس کی زندگی کا ایک اہم دن تھا۔ اس موقع پہ اس کی بیوی بھی اس کی خوشی میں برابر شریک تھی۔ اسی کی خدمت اور حوصلے سے تو وہ آ ج اس مقام تک پہنچا تھا۔۔۔۔۔۔۔۔

اس خبر کا انتظار اسے گزشتہ دو سال سے تھا ۔ وہ مسلسل اپنی محنت کا پھل پانے کے لئے آ ج تیار تھا ۔ یہ دن تھا اس کی محکمانہ ترقی کا۔۔۔۔۔

اس خبر کی اطلاع تو اسے نیم کلرک نے ایک مہینہ قبل ہی دے تھی۔ جب اس کی ترقی کا پروانہ مرکزی دفتر میں دستخط ہونے کا منتظر تھا۔ ۔۔۔

اس موقعہ کو یاد گار جانتے ہوئے اس نے نیا قیمتی لباس بھی تیار کروایا تھا ۔ گزشتہ اتوار کو وہ اپنی اہلیہ کے ہمراہ شہر کے سب سے بڑے شاپنگ مال میں کپڑے اور جوتے خریدنے گیا ۔ اس کی بیوی نے اپنے خرچ میں سے جمع کی گئی رقم سے مہنگے جوتے خرید کر تحفہ دیا۔ جو اس کی اس کامیابی کو اپنی کامیابی سمجھتی تھی ۔۔۔۔۔

آ خر کار 15 ستمبر کے دن کا سورج طلوع ہوگیا ۔ وہ معمول...

تحقیقات حدیث میں پروفیسر جوزف شاخت کی طرز تحقیق کا تنقیدی جائزہ

In general, the results of research studies conducted by Professor Joseph Schacht and his fellows on criticism of Ahadith are contradictory with the results of Muslim Scholars. Muslim Scholars, point of view is that Muhaddithin have opposed, with full power, the condemnable tries for fabrication of Ahadith. Valuable principles for the identification of authentic and unauthentic traditions were the result of the struggles done by Muhaddithin. With the help of these principles the categorization of Ahadith came in to practical. Professor Joseph Schacht argues that the material presented as Ahadith and Sunna of Prophet by Muslim scholars is the production of later times. According to his point of view, there is no authentic hadith in the bulk of traditions and if assumed that there are few authentic, they are also mixed up with unauthentic and there is no possibility of identification of authentic one. This study is a try to identify the mistakes of his research approach.

Becoming Leaders: the Life Histories of Male and Female Principals

The field of educational leadership has been a globally and nationally popular focus of research and discussions for past many years. In the same vein, a significant number of studies by the global and national scholars have explored different dimensions of leadership in education (Bana & Khaki, 2014; Bush & Middlewood, 2005; Khaki, Bana, Tajik, & Safdar, 2012; Khan, 2011; Nash, 2012; Panah, 2008; Simkins et al., 2003; Sultan, 2005). A review of these studies suggests an emphasis on the leadership practices of a leader and a very few studies have actually explored how a leader learns leadership and portrays various leadership practices, specifically in the context of Gilgit-Baltistan. To this end, the present study has examined the experiences of two school principals which seemed to have contributed to their journey of becoming leaders. In particular, this qualitative life history research explores experiences of one male and one female principals' journey of becoming a leader in two not-for-profit private higher secondary schools of Gilgit-Baltistan. The study revealed that the quality of educational institutions they attended, provision of leadership roles at home; on-the-job informal and formal mentoring opportunities, and ability to reflect on everyday personal and professional experiences greatly contributed towards preparedness of these leaders to assume leadership roles. These three factors made their transition into leadership roles smoother, easier and quicker. On the other hand, lack of mentoring opportunities, lack of quality education and discouraging home environment made their transition into leadership challenging. The study has shown the leaders in such situations learn through their own wisdom and reflection on previous practices. The life histories of both principals show the groundedness of leadership in the socio-cultural context. The male principal with early induction into teaching (paid job as a provider) had an extensive experience of teaching and leading schools. Similarly, the female principal had very protected environment with quality education throughout her schooling and university education. Though they experienced life differently, their learning and practices of building collegial and caring relationships and promoting shared sense of organizational policies seemed to be similar. Therefore, the study suggests that personal and professional life experiences (gendered), which shape leadership practices of a leader need to be seriously considered in the educational leadership discourse. Such consideration will allow much needed and relevant support to the female and male principals. Recognition and support to the efforts of female leaders, in particular, will encourage more women