IBN AL- HAITHAM J. FOR PURE & APPL. S CI. VOL.23 (2) 2010 Study the Effect of MgO Addition on Some of Physical Properties of ZnO S. k. Abd-Al Hassan Departme nt of physics , College of Education Ibn Al-Haitham, Unive rsity of Baghdad Abstract Different p ercents(1.0,2.5,5.0 and 10)wt%of M gO p owders were added to ZnO p owder to st udy their effects on the phy sical prop erties of ZnO.Density , p orp sity and water absorption of ZnO were decreased as M gO weigth p ercentage content increased. The values of vickers hardneess have double values esp ecially at 1.0 wt % of M gO. Introduction Ceramics have been widely app lied in engineering app lications due to their excellent resistance to heat, corrosion, and wear . Zinc oxide was the material of choice for this observation because it by far is the most common material used in the commercial manufacture and research due to its low cost and wide availability . It is valuable both for direct app lication or p reparation of other comp ounds[1-3]. Zinc oxide (ZnO) has been p roduced commercially for considerably more than century , originally for use as a p igment in p aints and also for rubber, glass, p orcelain enamels and p harmaceuticals[4-6].M ore recently, Zinc oxide has found new app lication in semiconductors, luminescence and p hotoconductivity [1-3] Zinc oxide varist ors are ceramic semiconductor devices with highly non–linear electrical behavior and greater energy absorp tion capabilities. This p rop erty allows t heir use in the p rotection of electric and electronic circuits, where as lightning rods remain the principal app lication . Zinc oxide is also transp arent to vissible light to a relatively high and uniform degree so that it exhibits a p ure white of high brilliance [7] . This research deals with the effect of magnesium oxide (M gO) addition on the p hy sical p rop erties of zinc oxide . Some researchers st udy ied the addition of the materials on ZnO such as : Lu et al [8] have st udied the effect of p orosity on the scaling of fracture st rength who showd that t he fracture st rength of ZnO ceramics is more influenced by the ratio of p ores and grain sizes. Ramires et al [6] have st udied the effect addition of SnO2 on ZnO on the mechanical p rop erties and found that the elast ic modulus of Z nO –SnO2 is doubled then ZnO only. Abdullatif [9] has st udied the effect of adding borax on the p rop erties of ZnO such as linear shrinkage, density which shows t hat the increase of the weight p ercent of borax would lead to reduce the linear shrinkage and increasing the bulk density . IHJPAS IBN AL- HAITHAM J. FOR PURE & APPL. S CI. VOL.23 (2) 2010 Experime ntal part Materials Zinc oxide p owder (p urity 99.5%) (Germany ) with small parctical size less t han 25µm has been used. M agnesium oxide has been p repared from magnesium salt (Boh) by heating the p owders to 600 C˚ for 1hr . Four weight p ercentages of M gO (1.0% ,2.5% ,5.0% and 10%) have been used. Poly vinyl alcohol was used as a binder (at 1.5%). 5 samples for each percents have been p repared . All the samp les sintered at (1300 C˚) using 5 C˚/min as a heating and cooling rate . The soaking time was 2 hrs. Equi pments M any equip ment have been used to p repare and test samples as follows:  Digital balance (0.0001 g) typ e (DNVER INSTRUM ENT).  Electrical oven ty p e (COOPER HEAT).  Hy draulic p ress (5 ton) type (BEGO) .  Electrical furnace (up to 1350C˚) type (RUHSTRAL)) .  M icrovickers harness type (TIM E GROUP) .  Gaindin g and polishin g machine ty p e (M ETASERV). Preparation of disc sample s Each percent of M gO p owder was mixed carefully with ZnO p owders by ball mill for 1 hr. The homogenized powder comp acted as a discs (10mm diameter and 10mm height) using 2 tons as a p ressure force. Characterization De nsi ty measurement Archemdise role has been used to calculate the app arent density according to ASTM (c373-71) and ASTM (c20-74) using the equation [10]. ρ =wd/(ws-wn) ……………………..(1) where : ρ= density ( gm/cm 3 ) wd = dry weight (gm) ws= saturated weight in water wn= lmmersed weight in water Porosi ty measurement According to ASTM (c373-72) the p orosity of the sintered sample was calculated by using the equation [10] . P% =(ws-wd)/(ws-wn) *100………………….…(2) Water ab sorp tion measurement According to the ASTM (c133 -81) the water absorp tion of the sintered sample was calculated by using equation [11]. W.A % =wS –wd/wd *100 ……………...…(3) where : W.A is water a absorp tion. Line ar shrinkage measurement By using the below equation the linear shrinkage was calculated as follows [11] : L.sh% = L0 –L/L0*100………………………..…..(4) where : L.sh= linear shrinkage. L0 = hight of sample before f irin g. IHJPAS IBN AL- HAITHAM J. FOR PURE & APPL. S CI. VOL.23 (2) 2010 L= hight of sample after firin g. Microvickers hardne ss measureme nt Equation below was used to measure the microhardness of the sintered sample as follows [10]: HV= 2p sin(136/2)/D 2 =1.854p /D 2 ………………………..…(5) Where : HV = Vickers hardeners (kg/mm 2 ) P= Ap p lied load . D= diameter of the indent (mm) Re sults and Discussion Table (1) and all figures showed the behavior of zinc oxide dop ed by the different p ercentages of magnesium oxide for most p hy sical p rop erties. Fig.(1) shows the effect of M gO weight p ercentage on the bulk density of zinc oxide. This behavior has a good correlation with the mixture role which is[9]: ρ = ρ1 v1 + ρ2 v2……………………….(6) where ρ is the density of the doped samp le ρ1 is the density of zinc oxide v1 is the volume fraction of zinc oxide ρ is the density of magnesium oxide v2 is the volume fraction of M gO. The density of ZnO is decreased as the M gO weight p ercentage is increased, that is clear because the density of zinc oxide is 5.606 g/cm 3 and the density of M gO is 3.58 g/cm 3 . Fig.(2) shows the effect of M gO weight p ercentage on the linear shrinkage of ZnO sample. The shrinkage is increased smoothly and then saturated at 1.0% and 2.5% then decreased at 10% and that may be due to the filling of the pores by M gO p articals [9]. Fig.(3) shows the behavior of the zinc oxide p orosity with M gO dop ed. It clearly showed that the porosity is decreased as the percent of M gO is increased. This behavior is p roved by the increase of Vickers hardness Fig.(4) shows the effect of M gO p ercents on the water absorp tion prop erty of ZnO, which shows t he water absorp tion is decreased smoothly as this behavior is similar to the p orosity behavior that is due to the pores found in the samples .All these values may be improved by increasing the sintering temp erature [12]. Fig.(5) shows that the Vickers hardness has nearly double value of the native ZnO, and also it is well known that the p orosity is inversely p rop ortional to the mechanical p rop erties. This increase in hardness may be due to the addition of M gO which may increased the cry st al growt h which caused the interconnecting of the grains [13]. Conclusions The phy sical prop erties of ZnO was affected by the addition of M gO additive where density , p orosity and water absorp tion have decreased as t he percent of M gO increased. IHJPAS IBN AL- HAITHAM J. FOR PURE & APPL. S CI. VOL.23 (2) 2010 Linear shrinkage has nearly a small variation but hardness is increased very obviously. Where the value of hardness is doubled than of pure ZnO (120HV). Re ference 1-Eda,E.(1980)"Degradation mechanism of non–ohmic zinc oxide Ceramics", J.A p p l.Phy s.51(5) 2678-2684 . 2- Levinson, L.and Philip p , H.(1986) "Zinc oxide varist ors A revew ceramic" Bulletin 65:(4)1-7 3- Gup ta,T.K.(1990) " Ap p lication of zinc oxide varist ors" J. of Amer. Cera.Soc. 73:(7)1817- 1840 . 4- Nahm,C.and Park,C. (2000)"M icrost ructure, electrical p rop erties and degradation behavior of PdO2 bsed ZnO dop ed with Y2O3"J.of M aterials Science 38:(12)3037- 3063. 5- Askeland, .D.R. and Fulay,P.P. (2005 )"The Science and Engineering of materials "Thomson -Engineering Fifth Edation, 156-160. 6- Ramirez,M .A.; M arcos,F.R.; Fernandes,J.F. and Varel, J.A. (2008) "M echanical p rop erties and dimensional effects of ZnO and SnO2-based varist ors"J.Am. Ceramic.Soc.91:(9)3105-3108. 7- Ramirez,M .A.;Simdez,A.Z. and M argnez,M .A. (2007) "Characterization of ZnO- degraded varist or used in high tension Device” M at.Res.Bull.42:1159-1168. 8- Lu,C.;Danzer,R. and Fischer,F. (2004), "Scaling of fracture st rength in ZnO effect of p ore/grain size introduction and p orosity ", J. of the European Ceramic Society , 24: 3643-3651. 9- ALSammaraey ,A.R. (1996), "Prep aration and characterization of zinc oxide p owder for ceramic industry ", Ph. D. Thesis, University of Technology , Baghdad – Iraq 45_75. 10-ASTM ,(1982) Part 17(c20-71) Bulk-density water absorp tion, ap p arent p orosity of white ware p roducts . 11-ASTM , (1986) Part 15.02(c373-71,72) water absorp tion, Bulk density , app arent p orosity of white water p roducts. 12-Alvarez-Fregose,Octaivo, (1994), "Sintering temp erature effects on the p erformance of ZnO ceramic varistors", Revista M exicana de Fisica, 40: (5) 771-781. 13- Dy son,R.D. and M orrel,R. (1982), " M echanical testing of engineering ceramic at high temp erature", J. Elsevier Ap p lied Science Itd.25-32. IHJPAS IBN AL- HAITHAM J. FOR PURE & APPL. S CI. VOL.23 (2) 2010 Table: (1) The physical propeties of doped ZnO MgO Percent Bul k density (gm/cm 3 ) Line ar shrinkage Appernt porosty Microhardne ss (Kg/mm 2 ) Water absorption 0.0 4.97 0.52 19.23 59.7 4.13 1.O 4.80 0.54 18.00 126 3.29 2.5 4.67 0.54 15.75 93 3.50 5.0 4.70 0.55 15.75 86.8 3.60 10 4.47 0.53 15.71 78.9 3.30 4.2 4.3 4.4 4.5 4.6 4.7 4.8 4.9 5 5.1 0% 1% 2.5% 5% 10% Mgo% B u lk d e n s it y Fig. ( 1) Vari ati on of bul k de n si ty of ZnO wi th MgO pe rce n ta ge IHJPAS IBN AL- HAITHAM J. FOR PURE & APPL. S CI. VOL.23 (2) 2010 0.45 0.48 0.51 0.54 0.57 0.6 0% 1% 2.5% 5% 10% Mgo% L in e a r s h ri n k a g e Fi g. (2 ) Variation of line ar sh rinkage of ZnO wi th MgO pe rcentage 0 5 10 15 20 25 0% 1% 2.5% 5% 10% Mgo % A p p e ra n t p o ro s it y Fi g .(3 ) Variation of apperant porosi ty of ZnO wi th MgO pe rcen tage IHJPAS IBN AL- HAITHAM J. FOR PURE & APPL. S CI. VOL.23 (2) 2010 0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 0% 1% 2.5% 5% 10% M go % W a fe r a b s o rp ti o n Fig .(4)Variation of water absorption of ZnO withMgO percentage 0 20 40 60 80 100 120 140 0% 1% 2.5% 5% 10% Mgo % M ic r o h a rd n e s s Fi g .(5) Variation of microhardne ss of ZnO wi th MgO pe rcentage IHJPAS 2010) 2( 32المجلد مجلة ابن الهیثم للعلوم الصرفة والتطبیقیة ى بعض الخواص الفیزیائیةفتاثیر اضافة اوكسید المغنسیوم ةدراس الزنـــك ألوكسیــد قاسم عبد الحسن شیماء جامعھ بغداد ،كلیھ التربیھ ابن الھیثم ،قسم الفیزیاء ةالخالصـ 1.0,2.5,5.0a% (نسب وزنیة أضیف nd10 ( ى فـمن اوكسـید المغنسـیوم الـى مسـحوق اوكسـید الزنـك لدراسـة تاثیرهـا ولقـد وجـد ان الكثافـة والمسـامة واالمتصاصــیة للمـاء تقـل الوكسـید الزنـك كلمـا ازدادت نسـبة االضــافة .الخـواص الفیزیائیـة لـه .من اوكسید المغنسیوم1.0% ة الوزنیة بفیكرز تضاعفت عند النس ةلوحظ ان قیمة صالد اال انه قد. الوكسید المغنسیوم IHJPAS