A STUDY OF OPTICAL PROPERTIES OF PHOSPHATE AND TELLURITE SEMICONDUCTING OXIDE GLASSES

Glass samples in the system of (P2O5)75-(CuO)25-x-(CdO)x/(P2O5)75-(CuO)25-x(ZnO)x/(P2O5)75-(CuO)25-x-(V2O5)x/(P2O5)50-(TeO2)50-x-(CdO)x/(P2O5)50-(TeO2)50-x-(ZnO)x and (P2O5)50-(TeO2)50-x-(V2O5)x glasses of different compositions where (x = 0, 5, 10, 15,20) were prepared by the melt-quenching technique. Optical absorption spectra of different compositions were recorded in the visible and UV regions and optical parameters such as optical energy gap (Eopt) and band tails (Eo) were determined by Urbach formula, the measurements for phosphate glasses of optical energy gap (Eopt) (P2O5)75-(CuO)25-x-(CdO)x have been determined and founded between (3.75-4.185) eV, (P2O5)75-(CuO)25-x-(ZnO)x the value of optical energy gap is between (3.75-4.25)eV, (P2O5)75-(CuO)25-x-(V2O5)x the (Eopt) is between (3.75-4.2)eV. for tellurite glasses the measurements of optical energy gap (Eopt) of (P2O5)50-(TeO2)50-x-(CdO)x have been determined and founded between (3.825-4.25)eV, (P2O5)50-(TeO2)50-x-(ZnO)x the (Eopt) is between (4.035-4.2)eV, (P2O5)50-(TeO2)50-x-(V2O5)x the value of optical energy gap is between (3.875-4.335)eV, It was found that the fundamental absorption of these glasses is dependent upon compositions and arises from forbidden indirect transitions. The most satisfactory results were obtained with the theory Davis and Mott for forbidden indirect transitions. Keyword: Optical properties, Oxide Glasses, Absorption Edge. Kirkuk University Journal /Scientific Studies (KUJSS) Volume 11, Issue 1, March 2016 , p.p(224-233) ISSN 1992 0849 Web Site: www.kujss.com Email: kirkukjoursci@yahoo.com, kirkukjoursci@gmail.com 225 ةــسا رد تايجاجزل ةيرصبلا تافصلا تافسوفلا ديساكا تويرمتلاو ةمصوملا وبشلا مع ي يمع دمحم ىفطصم 1 , نسح دبع فانم 2 1 نينبمل يدا زآ ةيدادعا / كوكرك ةظفاحم ةيبرتل ةماعلا ةيريدملا alimustafa20012001@gmail.com 1 2 كوكرك ةعماج / ةيمك ةفرصلا مومعمل ةيبرتلا / ءايزيفلا مسق 2 drmanafadb@yahoo.com :ثحبلا ملاتسا خيرات 11 / 11 / 2115 :ثحبلا لوبق خيرات 23 / 2 / 2116 صخمملا : تابكرملا ريضحت مت (P2O5)75-(CuO)25-x-(CdO)x / (P2O5)75-(CuO)25-x-(ZnO)x/(P2O5)75-(CuO)25-x -(V2O5)x /(P2O5)50-(TeO2)50-x (CdO)x / (P2O5)50-(TeO2)50-x-(ZnO)x and (P2O5)50-(TeO2)50-x(V2O5)x = ( ةفمتخم زيكا رتبو ةيجسفنبلا 0 , 5 , 10 , 15 , 20 يئوضلا صاصتملاا فايطا ميق انمجس مث , ) قطانملا يف عم ريغتت ةيرصبلا ةوجفلا ةقاط ناب انل جئاتنلا ريظو ةمزحلا لويذ ةقاطو ةيرصبلا ةوجفلا ةقاطل ميق و قوفلاو ةيئرملا كا رت ريغت ـ , رصانعلا زي تلااقتنا نم اشنتو ةريغتملا تابكرملا ىمع دمتعي تايجاجزلا هذيل صاصتملاا ةفاح ناب دجو دقو شابملا ريغ ـ ا قطانممل ةر ةروظحمل مو . ـ م اييمع لوصحلا مت يتلا جئاتنلا نأ حضاولا ن ـ امامت قفتت ةسا ردلا هذى للاخ ن م ـ يرظن ع ـ ة لا : ةلادلا تاممك صاصتملاا ةفاح ,تايجاجزلا ديساكا ,ةيرصبلا تافصلا . x


INTRODUCTION
Glass can be made with excellent homogeneity in a variety of forms and sizes such as rod tubes, sheets, plates… etc; from small fibers to meter-sized pieces. Furthermore, glass can be doped with rare earth ions and microcrystallines and a wide range of properties can be chosen to meet the needs of various applications. These advantages over crystalline materials are based on the unique structural and thermo dynamical features of glass materials [1]. Glass is in widespread use largely due to the production of glass compositions that are transparent to visible light. In contrast, polycrystalline materials do not generally transmit visible light [2].
The individual crystallites may be transparent, but their facets (grain boundaries) reflect or scatter light resulting in diffuse reflection. In the 21st century, scientists observing the properties of ancient stained glass windows, in which suspended nano particles prevent UV light from causing chemical reactions that change image colors, are developing photographic techniques that use similar stained glass to capture true color images of Mars for the 2019 ESA Mars Rover mission [3]. New chemical glass compositions or new treatment techniques can be initially investigated in small-scale laboratory experiments. The raw materials for laboratory-scale glass melts are often different from those used in mass production because the cost factor has a low priority.
In the laboratory mostly pure chemicals are used. Care must be taken that the raw materials have not reacted with moisture or other chemicals in the environment (such as alkali or alkaline earth metal oxides and hydroxides, or boron oxide), or that the impurities are quantified (loss on ignition) [4]. Evaporation losses during glass melting should be considered during the selection of the raw materials, e.g., sodium selenite may be preferred over easily evaporating SeO 2 . Also, more readily reacting raw materials may be preferred over relatively inert ones, such as Al(OH) 3 over Al 2 O 3 . Usually, the melts are carried out in platinum crucibles to reduce contamination from the crucible material. Glass homogeneity is achieved by homogenizing the raw materials mixture (glass batch), by stirring the melt, and by crushing and re-melting the first melt. The obtained glass is usually annealed to prevent breakage during processing [4,5]

Experimental Work
For the present study, Six groups of (P

RESULTS AND DISCUSSION
The optical absorption coefficient α (ω) near the band edge in many amorphous semiconductors and insulators shows an exponential dependence on photon energy (ћω) and obeys an empirical relation due to Urbach [9]:

α (ω) = α o exp (ћω / E o ) ……………… 1
Where ω is the angular frequency of the radiation, α o is a constant and E o is related to the width of the tails of localized states in the band gap. The absorption edge for non-direct transitions, having K-constant conservation selection rule in most amorphous and semiconductors [8] can be determined from the relation [10]:

α (ω) = A (ћω -E opt ) n / ћω ……………… 2
Where A is a constant, n is the power index and E opt is the optical energy gap of the material.
Practically the optical absorption coefficient α(ω) can be calculated from the relation:

α (ω) = 1/d ln ( I t / I o ) …………..………. 3
Where I t and I o are the intensities of the incident and transmitted beams respectively,corrected for any reflection at the first surface, and d is the thickness of the sample