2011) 2( 24مجلة ابن الهیثم للعلوم الصرفة والتطبیقیة المجلد للمركب الفائق التوصیل ةوالكهربائی ةتحضیر ودراسه الخصائص التركیبی Hg0.5Pb0.5-xSbxBa2Ca2Cu3O8+ δ كریم علي جاسم ، محمد عبد النبي ، مصطفى محمد علي ابن الهیثم، جامعة بغداد -قسم الفیزیاء، كلیة التربیة 2010، تشرین االول ،5: استلم البحث في 2011، شباط، 8: قبل البحث في الخالصة ــــــق ــــــات الزئبــ ــــــاص –حضـــــــرت مركبـ ــــ–الرصـ ـــــوني الفائقــــ ـــیل ذ ةاالنتیمــ ــیغ والتوصــــ ــــ -Hg0.5 Pb0.5 ةالصـ xSbxBa2Ca2Cu3O8+δ (x=0, 0.10 and 0.15) اسـتعملت .ثـالث خطـوات بطریقـة تفاعـل الحالـة الصـلبة باسـتعمال Hg0.5المركــب ةن عینــأووجــدنا Tcإلیجــاد درجــة الحــرارة الحرجــة (point probe 4) ةالكهربائیــة تقنیــة المقاومیــ Pb0.5Ba2Ca2Cu3O8.437 المركـب ةا عینـمـسـلوك شـبه موصـل بین وذاHg0.5 Pb0.4Sb0.1Ba2Ca2Cu3O8.353 هـي ةدرجـ والتوصـیل ذ ةهـي فائقـ Hg0.5 Pb0.35Sb0.15Ba2Ca2Cu3O8.233المركـب ةسـلوك معـدني موصـل لكـن عینـ وذ )Tc) ةانتقالی ةحرار 0ff)) 126تساويK . وأظهـرت هـذه ةتراكیب معینیه قائم ون المركبات ذأبینت تحلیالت االشعة السینیة االنتیموني تسبب ةنسب ةمقارنة مع الخالیة منه وان زیاد Sbاالنتیموني ةمع زیاده نسب cالتحلیالت نقصان في قیمة الثابت )Vphase)الطور ةفي نسب ةزیاد . c/aو ρM ةالكتلی ةونقصان في كال من الكثاف ((1223 ةالكتلی ةالكثاف، تحلیالت االشعة السینیة، درجة الحرارة الحرجة ، ةالكهربائی ةالمقاومی-:ةالكلمات المفتاحی IBN AL- HAITHAM J. FOR PURE & APPL. S CI. VOL.24 (2) 2011 Synthesis and Study Structural and Electrical Properties of Hg0.5Pb0.5-xSbxBa2Ca2Cu3O8+ δ Superconductors K. A. Jasim, M. Abdul-Nebi and M. M. Ali Departme nt of Physics, College of Education I bn-Al-Haitham, Unive rsity of Baghdad Received in : 5, October , 2010 Accepte d in : 8, February, 2011 Abstract M ercury -lead-antimony based sup erconductors with the formula Hg0.5 Pb0.5- xSbxBa2Ca2Cu3O8+δ (x=0, 0.10 and 0.15) have been p repared by useing three st ep solid st ate reaction p rocesses. Electrical resistivity , using four p robe technique, is used to find the transition temp erature Tc. It is found from that sample Hg0.5 Pb0.5Ba2Ca2Cu3O8.437 is semiconductor , sample Hg0.5 Pb0.4Sb0.1Ba2Ca2Cu3O8.353 is normal st ate with metallic behaviors, while sample Hg0.5 Pb0.35Sb0.15Ba2Ca2Cu3O8.233 is sup erconducting st ate with critical transition temp erature (Tc) is 126K. X-ray diffraction (XRD) analysis showed a tetragonal st ructure with decrease in the c-axis lattice constant for the samp les dop ed with Sb as comp ared with these which have no Sb content. It was found that the increase of the Sb concentrations of all our samples p roduce an increase of the volume fraction (Vphase ) and decrease c/a and M ass density ρM . Key words:- Electrical resistivity , Transition temp erature, X-ray diffraction and M ass density Introduction Sup erconductivity in the Hg-based cuprate family having the generic formula HgBa2Can- 1CunO2n+2 ([Hg-12(n-1)n], Hg-Ba-Ca-Cu-O, HgBCCO) was first reported in 1993 [1] for the n = 1 compound (Hg-1201). Shortly thereafter, a record high TC of 133 K was reported for the n = 3 comp ound (Hg-1223) under ambient conditions [2]. Subsequently , it was found that TC values in excess of 164 K could be induced in the Hg-1223 by the app lication of a high p ressure [3]. The Hg-1223 samples are known to degrade rapidly after sy nthesis. In view of this, significant efforts have recently been made to imp rove the st ability of the Hg bearing HT SC p hases, p articularly the Hg-1223 p hase. It is now known t hat t he most effective way to imp rove the st ability of the Hg-1223 p hase is through suitable cationic substitut ion for Hg. Ty p ically suited cations are those having oxidation states higher than that of Hg +2 greater than + 2 such as, Tl +3 , Pb, Bi +3 , and Re[4-7] . They bring in more oxy gen in the oxy gen deficient HgO δ lay er leading to p hase st ability . The higher oxidation st ate cations also lead to hole op timization in the hole deficient as grown Hg-1223 p hase, thus p roducing op timum critical transition temp erature (Tc). In the p resent work we have successfully p repared Hg0.5Pb0.5-xSbxBa2Ca2Cu3O8+δ bulk p olycryst alline sup erconductor by using three st ep solid state reaction p rocess, we have doped Hg0.5 Pb0.5Ba2Ca2Cu3O8+δ with Sb taken in varying concentrations st ability of Hg(Pb)-1223 p hase. Experime ntal The sy nthesis of Hg0.5 P b0. 5-xSbxBa2Ca2Cu3O8+ δ HT SC p hases (x= 0, 0.10 and 0.15) have p repared solid state reaction met hod , using app rop riate weights of p ure powders (99.998% IBN AL- HAITHAM J. FOR PURE & APPL. S CI. VOL.24 (2) 2011 from M ay & Baker LTD Dagenham England) materials of HgO, , P b2O3, Sb2O3,BaCO3, CaCO3 and CuO. The weight of each reactant was measured by using a sensitive balance ty p e (M ett ler H35 AR with Cap aci ty: 11 0 grams and Rea da bi lity: 0. 001 ).T he synt hesis of t he samples have been carried out by t hr ee st ep precursor met ho d. In t he first st ep, the powders (BaCO3, CaCO3 and CuO)were mixed together by using agate mortar ; a sufficient quantity of 2- p rop ane was to homogenization the mixture and to form slurry during the p rocess of grinding for about (30-50) minute.The mixture was dried by an oven at (200 0 C). The mixture was p ut in tube furnace that has p rogrammable controller ty p e [Eurp therm 818], for calcinations, which is the heat treatment to remove CO2 gas from the mixture. For this p rocess the p owder was heated to temp erature of (800 0 C) for three hours with a rate of (200 0 C /hr) , then cooled to room temp erature by the same rate of heating. In the second step, the Ba2Ca2Cu3O7 p recursor was mixed with HgO, Sb2O3 and Pb2O3 to obtain the nominal comp ositions Hg0.5 Pb0.5-xSbxBa2Ca2Cu3O8+δ where x=0.0, 0.10 and 0.15. The powder was p ressed into disc-shap ed p ellets (1.3 cm) in diameter and (0.2-0.3 cm) thick, using hy draulic p ress ty p e (Sp ecac) under a p ressure of 8 ton/cm 2 .The p ellets were p resintered in air at (855-860) 0 C for (8 hours) with a rate of (200 0 C/hr) and then cooled to room temperature by same rate of heating. In the third st ep, the pellets were reground, repressed and resintered in the oxy gen (oxy gen rate 0.6 L/min) at the same range of temp erature for further (12 hours) and then cooled to (500 0 C) and annealed in oxy gen for (4 hours) and then cooled to room temp erature by the same rate of heating. The samples were examined with resistivity exp eriments by using st andard four-p robe technique which is most common method of determining the Tc of a sup erconductor. T he samp le was fixed in the cry ost at inst rument which was joined to a rotary p ump to get a pressure of 10 -2 mbar inside the cry ost at, and also joined to a sensor of digital thermometer (ty p e Pt 100 resistance to t emp erature detection RTD) near the samp le p osition . A 10 mA current was sup p lied to the sample by a current source D.C p ower sup p ly ty p e (Electronica- Veneta DV 30/V3); the voltage drop was measured by a Keithley model 180 nanovoltmeter with sensitivity of a bout  0.1 nanovolt was used for voltage measurements. The resistivity (ρ) could be found from the relation: ρ = L t I V  Where : I is the current p assing through the samp le, V is the voltage drop across the electrodes, ω is the width of the sample, L is the effective length between the electrodes, t is the thickness of the sample. All measurement of L, t and ω were made by using digital vernier. The exess of oxy gen content (δ) could be determined by useing chemical method called Iodometric titration.The st ructure of the p repared sample was obtained by using x-ray diffractometer (XRD) ty p e (Philip s) which have the following features, the source Cukα current (20 mA), voltage (40 KV) and λ=1.5405 A 0 . A comp uter p rogram was established to calculate the lattice p arameters a,b,c this p rogram is based on Cohen , s least square method.The volume fraction of any p hase (Vphase ) in the sample were determined by using the relation(14): Vphase =      InII Ia ......21 x100 Where Ia is the XRD p eak intensity of the p hase which were determined,I1,I2,…In are the peaks intensity of all XRD. A computer p rogram was est ablished to calculate the lattice p arameters a,b,c this p rogram is based on Cohen , s least square method[8]. Results and Discussion The temperature dependence of the electrical resistivity (ρ) for Sb free sample and samples with different Sb contents (x=0.1 and x=0.15) in Hg0.5 Pb1-xSbxBa2Ca2Cu3O8+δ) are shown in figure (1). It is found from this figure that the behavior of resistivity with temp erature of the comp osition which has no Sb is semiconductor while the addition of Sb content in the Hg0.5 Pb1-xSbxBa2Ca2Cu3O8+δ) transform from normal state at (x=0.1) to sup erconducting st ate at IBN AL- HAITHAM J. FOR PURE & APPL. S CI. VOL.24 (2) 2011 x=0.15(T he value of critical transition temp erature (Tc( off )) for as grown Hg0.5 Pb0.35Sb0.15Ba2Ca2Cu3O8+δ p hases is 126K). T his behavior is due to the fluctuation of oxy gen excess and the increasing of Sb, while may lead to metastable st ructure, that decrease Tc, but most of them x=0.15, transform the st ructure to a st able p hase. A small amount of Sb addition is quite effective in decomposing the low-Tc p hase (1212) of Hg(Pb)Ba2Ca2Cu3O8+δ sup erconductor sy st ems by p roducing BaHgO3 and BaCuO2 accomp anied by high-Tc p hase formation. The destruction of the low p hase by Sb at the early st age may enhance the nucleation and the formation of high-Tc p hase. Enhancement of free Sb will raise the resistivity and this will, much more, increase BaPbO3 which is an insulator consisting of Hg- O. The XRD data collected from various samples (samples having various Hg, Pb, Sb Ca, Ba and Cu concentration) were all p olycryst alline and corresp ond to Hg(Pb,Sb))-1223 p hases. The XRD also shows some imp urity p hases with vanishingly small concentrations. The representative XRD p att erns are shown in figures(2 ). It could be seen from the sp ectra that there were three main p hases in all samples of the Hg-base sy st ems, high-Tc p hase (1223) reflections (p eaks H), and Low –Tc p hase reflections (p eaks L)and a small amount of imp urity p hases of (Ca, Ba)2CuO3, CaPbO4, CaSbO4 and CuO. The app earance of more than two p hases could be related to the st acking faults along the c-axis. The comp arison between the relative intensities of XRD p att erns for the samples with Sb=0, 0.1 and 0.15, with the relative intensity of the same reflections of the samp le with Sb=0 shows t hat all the samples have reflection intensity of the High-Tc p hase reflections and Low –Tc p hase reflections the H-p eaks increased and Low-T c decreased by increasing Sb . The High-Tc p hase reflections of the free sample (Tl= 0) has lower intensity than samples have Sb . The lattice p arameters have been estimated using d-values and (hkl) reflections of the observed x-ray diffraction p att ern through the soft ware program), the parameters a, b, c , M ass density ρM and volume fraction (Vphase ) shown in table(1).Figures (3), (4), (5) and(6) show an increase of the volume fraction (Vphase ) and decrease C, C/a and ρM for Hg-dop ed samp les for different comp osition of Hg0.5 Pb0.5-xSbxBa2Ca2Cu3O8+δ as comp arable with the free Sb sample. Conclusions We have sy nthesis of Hg0.5 Pb0.5-xSbxBa2Ca2Cu3O8+δ HT SC p hases (x= 0, 0.10 and 0.15) have p repared solid st ate reaction method. It is found that the behavior of resistivity with temp erature of the comp osition which has no Sb is semiconductor while the addition of Sb content in the Hg0.5 Pb1-xSbxBa2Ca2Cu3O8+δ transform from normal st ate (x=0.1) to sup erconducting st ate x=0.15(T he value of critical transition temp erature (Tc( off )) for as grown Hg0.5 Pb0.35Sb0.15Ba2Ca2Cu3O8+δ p hases is 126K). The increasing of Sb leads an increase of the volume fraction (Vphase ) and decrease c/a and ρM for samples for different comp osition of Hg0.5 Pb0.5-xSbxBa2Ca2Cu3O8+δ . Re ferences 1. Put ilin ,S. N.; Ant ipov, E. V, O.; Chmaissem, M.and Marezio, (1993) ,Superconduct ivit y at 94 K in HgBa2Cu04+ , Nat ure 362 ,226-228. 2. Schilling, A.;Canton i M.;Guo J. D.an d Ott , H. R. (1993) ,Superconduct ivity above 130 K in t he Hg– Ba–Ca–Cu–O system, Nat ure 363, 56. 3. Chu, C. W.; Gao, L.; Chen, F.; Huang, Z. J.; Meng, R. L.an d Xue, Y. Y. (1993) ,Supercon duct ivity above 150 K in HgBa2Ca2Cu3O8+ at high pressures, Nat ure 365 ,323-225. 4. Jassim, K. A. (2009) Influence of simult aneous dopin g of T l on t he t ransition temperat ure T c and t he latt ice parameters of HgBa2Ca2Cu3O8+ δ supercon ductors) Ibn Al-Haitham Journal for pure an d applied sciences, , Baghdad universit y, college of Ibn Al-Haitham ,Baghdad,Iraq 22(3): 86-92. 5. Jassim, K.A. (2005) Comp arison St udy of T c Between the Superconduct ing Compounds Bi2- x( Hg,P b)x Sr2-y BayCa2Cu3O10+ δ and Hg1-xP bxSr2-y BayCa2Cu3O8+δ , P h.D T hesis , Universit y of Baghdad , College o f Science , Phy sics Dep. Iraq IBN AL- HAITHAM J. FOR PURE & APPL. S CI. VOL.24 (2) 2011 6. Rajiv Giri, G. D.; Verma, R. S.; T iwari and O. N. (2003) Srivastava (Influence of simult aneous dopin g of T l and Bi on micro st ruct ure and crit ical current densit y of HgBa2Ca2Cu3O8+ d ) Cryst. Res. T echnol. 38(9):760 – 766 7. Su J. H, Sastry P . V. P S S an d Sch wart z, J. (2003) (Magnet izat ion and t ransport properties of silver-sheathed (Hg, Re)Ba2Ca2Cu3O8+δ t apes) Supercond. Sci. T echnol. 16 , 1134–1138 P II: S095 3-2048(03) 64411-8 8. Ferguson, I.F. an d. Rogerson, A.H. (1984) , A program for the calculat ion of the intensit ies of x-ray or neutron powder reflect ions, part 3) , Comput. Phys. Commun., .32, (Issue 1),. 83-94. Table(1): Values a,b,c ,c/a, δ and ρM for the samples for different composi tion of Hg0.5 Pb0.5-xS bxBa2Ca2Cu3O8+δ Fig. (1): Te mperature dependence of resistivity for Hg0.5 Pb1-xS bxBa at indicated values of (S b) at x =0.00, 0.10 and 0.15 X Tc(O FF )(K) Tc(O N) (K) δ(o2) a(A 0) c(A0) c/a ρM (g/cm 3) VPh-1223 0.0 0 ------ ------ 0.437 3.8 42 15 .99 4.1 61 5.9765 39.44 0.10 ------ ------- 0.353 3.8 44 15 .91 4.1 39 5.7351 55.17 0.1 5 12 6 135 0.233 3.8 43 15 .66 4.0 75 5.5841 75.79 IBN AL- HAITHAM J. FOR PURE & APPL. S CI. VOL.24 (2) 2011 Fig(2) XRD Patterns for the sample Hg0.5 Pb0.5-xS bxBa2Ca2Cu3O8+δ for x=0.00, 0.10 an d 0.15 15.6 15.7 15.8 15.9 16 16.1 0 0.02 0.04 0. 06 0. 08 0.1 0.12 0. 14 0. 16 conce ntrati on Sb C ( A ) Fig.(3): parameter C as function of dife rent S b for Hg0.5 Pb0.5-xS bxBa2Ca2Cu3O8+δ IBN AL- HAITHAM J. FOR PURE & APPL. S CI. VOL.24 (2) 2011 30 40 50 60 70 80 0 0.02 0.04 0. 06 0. 08 0.1 0. 12 0.14 0.16 Concentrat ion Sb V o lu m e F ra c ti o n % Fig.(4): volume fraction (Vphase) as function of diferent S b for Hg0.5 Pb0.5- xS bxBa2Ca2Cu3O8+δ 15. 6 15. 7 15. 8 15. 9 16 16. 1 0 0.02 0.04 0.06 0.08 0.1 0.12 0.14 0.16 co ncentrati on Sb C ( A ) Fig. ( 5): C/a as function of S b concentration for Hg0.5 Pb0.5-xS bxBa2Ca2Cu3O8+δ 5.5 5.6 5.7 5.8 5.9 6 0 0.02 0.04 0.06 0.08 0.1 0.12 0.14 0.16 Concen tra tion Sb M a s s D e n s it y ( g r a m /c m ) Fig. (6): Mass De nsity ρM as function of S b concentration for Hg0.5 Pb0.5- xS bxBa2Ca2Cu3O8+δ