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Home > Ln3+ Ions Doped Phosphate Glasses for Solid State Lighting Applications

Ln3+ Ions Doped Phosphate Glasses for Solid State Lighting Applications

Thesis Info

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Author

Shoaib, Muhammad

Program

PhD

Institute

Abdul Wali Khan University

City

Mardan

Province

KPK

Country

Pakistan

Thesis Completing Year

2019

Thesis Completion Status

Completed

Subject

Physics

Language

English

Link

http://prr.hec.gov.pk/jspui/bitstream/123456789/12208/1/Muhammad%20shoaib%20physics%202019%20awk%20prr.pdf

Added

2021-02-17 19:49:13

Modified

2024-03-24 20:25:49

ARI ID

1676726590981

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In present study, Lanthanide ions doped oxide and oxyfluoride phosphate glasses were prepared through melt quenching technique. Subsequently, properly cut and polished samples were studied through XRD, FTIR, density, refractive index, absorption spectra, photoluminescence spectra, X-rays induced luminescence spectra, JO analysis, lifetime study and CIE coordinates analysis. The recorded XRD pattern show broad bands without any sharp peaks which show that these glasses are amorphous in nature. The FTIR results show that the band corresponding to OH vibrations decrease in oxyfluoride glass samples compared to the oxide glasses. The decrease in the intensity of OH group bands, is due to the decrease of amounts of OH in the glass composition by reaction with fluorene to produce HF. The measured density shows the overall increasing trend with increase in the rear earth concentrations and also the densities of oxide glasses are higher than the oxyfluoride glasses which show that the structures of oxide glasses are more compact than the oxyfluoride glasses. The absorption spectra (Uv-Vis-NIR region) contain the corresponding doped rare earth ions transitions peaks. For Dysprosium (Dy3+), Samarium (Sm3+) and Europium (Eu3+) ions doped glasses most intense peaks correspond to 6H15→6H9/2+6F11/2, 6H5/2→6F7/2 and 7F0→5L6 transitions, respectively. The positions of the absorption bands are slightly change with change in the glass compositions. Similarly, the recorded excitation spectra of present glasses have corresponding Sm3+, Eu3+ and Dy3+ transition peaks along with the Gd3+ ions transitions peaks. Subsequently, the recorded emission spectra show the energy transfer from excited Gd3+ ions to Dy3+, Sm3+ or Eu3+ ions present in glass compositions. The transitions 8H5/2→6P3/2, 7F0 →5L6 and 6H15/2→ 4M15/2 + 6P7/2 are the hyper sensitive transition for Dy3+, Sm3+ and Eu3+ respectively. The emission spectra recorded at the respective wavelength observed for hypersensitive transitions in excitation spectra demonstrate that the oxyfluoride glass samples show comparatively higher emission intensity. The emission intensities increase with increasing RE3+ ions concentrations up to 1 mol% in the case of Dy3+ and Sm3+ ions doping there after start decreasing. While in the case of Eu3+ ions, the emission intensity upsurges and no luminescence quenching observed in 0.0 to 2.0 mol% concentration range. It is believed that the concentration quenching occurs due to non-radiative energy transfer among the RE3+ ions through cross relaxation channels. In X-rays induce luminescence spectra studied in present work show same trend and number of emission peaks as that of photoluminescence emission spectra but with different intensity and slightly different peaks positions due to the different irradiation sources. Several radiative properties i.e., Branching ratio, quantum efficiency, radiative lifetime, stimulated emission cross sections and radiative transition probabilities were calculated with JO theory. Lifetime of present glasses were recorded with respective emission and excitations wavelength and it is found that lifetime decrease with increasing concentration of Dy3+ and Sm3+ ions, while for Eu3+ ions no significant variations observed in lifetime values. Moreover, lifetime curve shows single exponential nature at lo wer concentration of rare earth and deviate from the single exponential behavior as the concertation of rare earth increase. This non-single exponential behavior of lifetime curves are fitted in the framework of Inokuti-Hirayama (IH) model to understand energy transfer mechanism involved in respective case. Subsequently, the color of emitted light was compared with 1931 CIE (Commission International de I’Eclairage) chromatic color coordinates.
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ہوٹل والے کا بچہ

ہوٹل والے کا بچہ

اک ہوٹل والا بے چارہ
چائے ہے بناتا دن سارا
ہوٹل کا چولہا جلتا ہے
تو گھر کا چولہا چلتا ہے
اُس کا چھوٹا سا بیٹا ہے
دن سارا چائے دیتا ہے

برتن دھوتا تھک جاتا ہے
چائے دے دے اَک جاتا ہے
ہم دن بھر چائے پیتے ہیں
سب چھوٹو چھوٹو کہتے ہیں

اُس کے ہم عمر سبھی بچے
جاتے ہیں سکول اپنے اپنے
ہر شام پتنگ اڑاتے ہیں
پیزا ، برگر بھی کھاتے ہیں
کھیلیں ، کودیں ، بھاگیں ، دوڑیں
اک دوجے کے دھاگے توڑیں
چائے دینا ، برتن دھونا
کیا اُس بچے کی قسمت ہے؟

کتنے ایسے بچے ہیں جو
چھوٹو ، نکّو ، ساجو ، طوطی
بھولا ، بالا ، کالا ، جیلا
جانے کیا کیا کہلاتے ہیں
بچے یہ کہاں سے آتے ہیں؟

تولیدی اور جنسی صحت: اسلامی تعلیمات کی روشنی میں

Human is the combination of body and spirit, Islām pays attention to the balanced growth and construction of the human personality considering the health of both body and spirit. As Muslims, we believe that Islām is the perfect code of life, which provides guidance for the solutions of all individual and collective problems of human beings. Therefore, we believe that Islām has a complete system of instructions for the development and reformation of spirit on the one hand, and, on the other hand, it has prescribed guidelines for the upkeeping and maintenance of the body. Reproductive and sexual health is one of the major problems of human beings. Eastern societies are comparatively shy to discuss this problem, unless necessary, while the western societies have introduced sex education in their schools to teenagers. We being Muslims tend to look towards our religion to guide us in such a way, that it may educate us, on the one hand, and on the other, it may guide us to adopt the required attitude to avoid the negativity of its awareness. Although the issue of reproductive health is considered as the specialty of the modern age, however, Islamic instructions very obviously discuss them from the beginning. In this article, the author has explored and elaborated Islamic teachings regarding the reproductive health and sexual instructions and discussed them in order to prove that Islām has the full capacity to solve the current social problems of reproductive health and sexual health.

Linearization of Higher Order Differential Equations

Lie''s method for converting a scalar second order ordinary di erential equation (ODE) to linear ODE by point transformations was already extended to third and fourth order scalar ODEs by point and contact transformations and to the systems of second order ODEs. The point symmetry group classi cation of linear nth order scalar and second order systems of m ODEs was provided. Till recently no work on the linearization and classi cation has been done for higher order systems of ODEs and scalar ODEs linearizable via point, contact and higher order derivative transformations. In this work, we use Meleshko''s algorithm for reducing fourth order autonomous ODEs to second and third order linearizable ODEs and then applying the Ibragimov and Meleshko linearization test for the obtained ODEs. This method can be applied to solve those nonlinear ODEs that are not linearizable by point and contact transformations. Complex-linearization of a class of systems of second order ODEs had been studied with complex symmetry analysis. Linearization of this class had been achieved earlier by complex method, however, linearization conditions and the most general linearizable form of such systems have not been derived yet. It is shown that the general linearizable form of the complex-linearizable systems of two second order ODEs is (at most) quadratically semilinear in therst order derivatives of the dependent variables. Linearization conditions for such systems are derived in terms of coe cients of the system and their derivatives. Further, complex methods are employed to obtain the complex-linearizable form of 2?dimensional systems of third order ODEs. This complex-linearizable form leads to a linearizable class of these systems of ODEs. The most general linearizable form and iv linearization conditions for such class of 2?dimensional systems of third order ODEs are derived with complex-linearization. A canonical form for 2?dimensional linear systems of third order ODEs is obtained by splitting the complex, scalar, third order, linear ODE. This canonical form is used for the symmetry group classi cation of 2?dimensional linear systems of third order ODEs. Five equivalence classes of such systems with Lie algebras of dimensions 8, 9, 10, 11, and 13 are proved to exist. Contact and higher order derivative symmetries of scalar ODEs are related with the point symmetries of the reduced systems. Two new types of transformations that build up these relations and equivalence classes of scalar third and fourth order ODEs linearizable via these transformations are obtained. Four equivalence classes of these equations are seen to exist.