Dharmaprakash, S M

Shettigar, V

IACS Institutional Repository

Indian J. Phys. 73A  (4). 503-509 (1999)U P  .~ an intcmiUional |ouma)Physical characteristics of ba^um cadmium formate crystalsV S h e ttig a r and  S M  D harm ap rak ashDepartment of Physics. Mangalore Univcreity, Mangalagangotri-574 199.Kumotaka. IndiaReieived 10 July 1998, accepted J December 1998Abstract : Barium cadmium formate hydrate (BCF) crystals with molecular tormula Bao53Cd()47(HCOOb.H20 have been grown from aqueous solution by slow cooling The grown crystals were charactcri/ed by atomic absorption specliomcfi*y. X-ray dillraciion, intrared spectral techniques BCF crystallizes in monoclinic system with unit cell dimensions a -  13,611 A: h -  13 241 A, r = I I.SX7 A, P -  31.9° and space group P2\/C. IIV n \ IR spectra levealcd that BCF crystals are optically transparent in the region 250-2100 nm. BCF is biaxial and is strongly anisotropic. Thermogravimetric analysis earned out on BCF indicate that the material is .stable upto 95X  The data of the electrical parameters combined with the thermal data was used to understand ihc mechanism of conduction BCF crystals exhibit low detect contcnlialionKeywords : C'lystal growth, characterization PACS Nos. : 61.10 Nz. 81 lO.Dn, 81 70 Pg1. IntroductionC ry sta ls  o f  fo rm a te  fam ily  [I~51 ex h ib it m arked  n o n lin ea r op tica l (NLO) p ro p ertie s . Of these, li th iu m  fo rm ate  h y d ra te  to g e th e r w ith  a se ries o f  so lid  so lu tion  based  on it, h as  the g rea test o p tica l non lin earity  and  are  w idely  used in quan tum  elec tron ics. W ith  an increasing  dem an d  o f  m a te ria ls  fo r n o n lin ea r op tica l app lica tions, investiga tions on c ry s ta lliza tio n  and  ch a rac te riza tio n  o f  new  m ate ria ls  are  rece iv ing  g rea t im portance : T h e  ex is tence  ol b a rium - cad m iu m  d o u b le  fo rm a te s  w ith  v a rio u s  p h ase s  in a  w ide  ran g e  o f  b a rium  lo rm a tc  an d  c ad m iu m  fo rm a te  c o n c e n tra tio n s  w as in d ica te d  by N ad zh a ry an  et al [6 ]. E v e n th o u g h  barium  cad m iu m  fo rm a te  s in g le  c ry s ta ls  w ere reported  [7], the co n ccn ta tio n  o t  b a n u m  and  cad m iu m  in th e  g ro w n  m a te ria l w ere  n o t d e te rm in ed . T h e  p re sen t p ap e r re p o r ts  on  th e  p h y s ic a l  c h a r a c t e r i s t i c s  o f  b a r iu m  c a d m iu m  fo rm a te  w ith  m o jc c u la r  fo rm u la  Ba„ ,,C d o  47(H C 0 0 ) . .H , 0 .73A(4>4) ©19991ACS504 V Shettigar and S M Dharmaprakash2. E xperim entalIn order lo investigate the crystallization condition of barium cadmium formate (BCF) pure phase, ( 1- jt) Ba(HCOO )2 + (jr) Cd(HCOO>2 system in water was investigated at 30°C, where .v = 0 .1, 0.2, 0.9. The solution yielded small plate like and needle like crystals indifferent experim ental vessels after about 36 hours o f solution evaporation at 30 X . Crystaiiization of new, pure and mixed phase were identified using atomic absorption spectrometry, thermal analysis, infrared and X-ray diffaction techniques. Pure phase single crystals of BCF resulted when the value of x  was 0.5 in the solution system. For = 0,1, along with barium formate and cadmium formate small traces of barium cadmium formate were present in the multiphase crystals. For the remaining x  values along with BCF, cadmium formate and barium formate multiphase crystals were observed.The presence of Ba^ **^ , Cd^^ and (HCOO)^ in BCF were confirmed by the chemical analysis. The concentration o f Ba^+ 0.53 and Cd^^ = 0.47 (when jc =s 0.5) was estimated from the atomic absorption spectroscopy and hence the molecular formula for BCF is Bao.5iCdo47(HCOO)2.H2 0 . The solubility diagram o f BCF is shown in Figure I. The resultant data could be fitted to a curve following the equation S =  a T ^  + h T  +  c, where S isFigure 1. Solubility curve for BCF crystal in >vater.the solubility expressed in gram/100 ml, T is the temperature in ®C. The constants evaluated arc a «  0.0173; 6 = -  0.01035 and c = 1.48036. The temperature coefficient of solubility is positive. This indicates that slow cooling could be tried as a crystal growth method. Large single crystals o f  BCF were grown using solution growth technique, by means o f mechanised cooling process between 50®C and 30®C. The resulting crystals were of the size (Figure 2 ) 35 x  12 x  14 m m l The growth rate o f  the crystal was high along 'C  axis and nearly equal along a and b directions. The growth velocities ranged between 0.2 and 0.4 mm/day.Physical characteristics of barium cadmium formate crystalsP late /F ig u re  2. BCF single crystals.Pliysu iil t luiracterisrics o f  baritim  la d iu im t form ate crystals 5055. Results and discussion|>(n^clcI• X-ray d itiraciion  pattern (Figure 3) o f the grown crystal were obtained using I'hilips I’M W 20 cliriractometcr with CuK„ radiation (A = 1.5418 A). Interplanar spacing 'ct .iiul I//A/1 \ allies for the palnes are indicated in the Figure 2. Single crystal X-ray diffractionFigure 3. I* vvcicr X-ia\ ciittraLiion paiiorn ot BCF ciystalanalysis was carried out using Enraf CAD 4 dilTractomctcr. The unit cell dim ensions o f  BCF arc a = 1.3.611 A; 6 = 13.241 A; c = 11.887 A; /3 = 3 1.9; :  = 4; space group P 2 ,/C  and svsicm  inorujclinic.Fijsurc 4, InlVarecI specna of BCF cnslalInlrarocl spectra (Figure 4) for BCF crystals were recorded using Perkin Elm er spcclropholom cler in the range 4()0-4(K)() cm *. The iniornialion obtained Irom the IR ''Peci-mi is summarised in Table I. The absorption peaks correspond to the molecular group \ib ra lions. According to the theories ol inirared spectra (8J and the standard infrared spectra o f metal form ates 19K the relations of m olecular group vibrations and the characteristic absorption bands were obtained.506 V Sherri$*ar a n d  S  M  D harnuiprakashA M etier TA 4000 thermal analyser system was used to study the thermal stability ol BCF at a heating rate of lO X /m in in air. Figure 5 depicts the thcrmogravimetric analysisWtIftNT 6AINFigure 5. TGA and DTG ciines for BCF crystaliTCiA) and differential thermogram (DTG) curves recorded simultaneously. Examination of ihe TGA and DTG curves indicates on the one hand the presence o f crystallization waterTabic I. Assignment of infrared frequencies (cm” *) for BCF crystal.IX’scnpdon Assignment FrequencyO ’H *;treich '^1 2810, 2890Symmetric OCC) stretch V2 1395. 1435. 1445Suiimen ic OC’O deformation 750, 780Asv mmciric OCO stretch ''4 1630, 1660Asymmetric OCO deformation 1420, 1440Out of plane C-H deformation 6^ 1030, 1070 1090, 1130molecule and on the other hand that the transformations are associated with mass changes and there is no physical transformations independent o f mass change. From the curves it is clearly understood that BCF is stable upto 95°C. At this temperature it losses the water molecule from its lattice. Taking either the weight percentage o f the end product or the initial weight as standard, the course o f transition is analysed with reference to the m olecular weight o f BCF. It is observed that BCF contains one m olecule o f  water o f crystallization.’Figure 6 d isplays the optical lran.smission spectra o f BCF single crystal with thickness 2 mm, recorded using a Hitachi U3400 UV vis IR spectrophotometer in the range 2(X^22(X) nm. BCF is transparent in 250-1400 nm region. In the entire visible region the absorption coefficient is about 0 .1 . Three plates parallel to the crystal physical axis o f BCFP hysical characteristics o f  barium  cadm ium  fo rm a te  crystals 507were prepared for the determination of the refractive indices in the wavelength region 4000 A -  7000 A, by the Brewster's angle method [ 10). Figure 7 shows the variation of refractive index with wavelength for BCF crystal. BCF is biaxial and strongly anisotropic.Figure 6. Optical transmission spectra of BCF single crystal.Figure 7. Vanation of refractive index with wavelength.Figure g. Variation of dielectric constant of BCF single crystal with frequency.The electrical param eters such as dielectric constant, (Figure 8) and dielectric loss (Figure 9) o f BCF single crystals perpendicular to c-axis were measured using an LCR508 V S h ettiga r a n d  S  M  D h a rm a p ra k a shm eter in the frequency range I KHz-4(XX) KHz at room tem perature. The dielectric constant and dielectric loss decrease with increasing frequency. The variations observed at low frequencies arc due to factors like impurities, grain boundaries and crystal defects [ 1 1J.Figure 10. Variation of dielectric constant (A) and a.c. conductivity (0) with temperature.Small value o f  dielectric loss in the BCF crystal indicates low concentration o f  defects in the m aterial. The dielectric constant and a.c. conductivity (Figure 10) o f BCF single crystals were also determined at varying temperatures in the range 2 7 X - 1 5 0 X  for 10 KHz. Considerable anam oly in the dielectric and conductivity values were not observed in the temperature region 30®C-90°C. There is a marked change in the dielectric and conductivity values at around 95®C, which is due to the dehydration o f  hydrated BCF into its anhydrous form. The dehydration tem perature as determ ined from the conductivity m easurem ents coincide with the dehydration peak values o f BCF.Physical characteristics of barium cadmium formate cry stals 5094. Conclusions( 1 ) S ing le  c ry s ta ls  o f  barium  cadm ium  fo rm ate w ith m o lecu lar form ula Biios(Cdo47(HCOO)2.H iO  have been grown from aqueous solution by slow cooling method.(2) BCF crystallizes in the monoclinic system with space group P2fC .(3) The results o f thermal analysis indicate thiit the BCF crystals arc thermally stableuntil about 95°C  and there is no physical transform ations independent o f mass changes. '(4) X-ray pow der diffraction reveals the crystaflinity o f the material.(5) Small value of dielectric loss indicates low concentration o f defects in BCF single crystal.A cknow ledgm entOne ol us (SM DP) thank the Department o f Science and Technology, Government of India, loi providing financial assistance to carry out this work.ReferencesM .S .Smgh. W A Bonner. J R Poiopowio? and L G Vanllileii A/>/>/ PIiyi Lein 17 2‘12 (1970)P .S Beichihold and S Haussuhl Appl Pliys. 14 403 (1977)1. M Bcluaev, L M Dorozhkin, L V Sotmleva, B A Chayanov, V D Shigorin and G P Shipulo So\ PIm C nsiallofir 24 484(1979)II' Dcsernoand S Haassuhl lE E E J Q um t Elec iron QE8608 (1972)H Ito. H Naito and H Inaba lELE Quani Elec Iron QEIO 247 (1974)K ,A Nad/haryan. L S llkina and IN Lepeshkov 7Ji NeorK Kliiim 25 1676 (1980) t Pelikinski and W Kolasinski Res Bull 17 I.S57 (1982)L J Bellamy The Inlnired Spec irci of Complex Molerulec (New York Academic) ( I9.S8)|9| JI) Donaldson, J F Knifion and S D Ross Spec iroc him Ac in 20 847 (1%9)10) R S .Sirohi A course o) expenmenis wiih He~Ne loser (New Delhi Wiley Eastern) (1983)111 K V Rao and A Smakula J  Appl P ins 36 2701 ( i 96.*))|21IM|4 ||3||6||7|iX|

Physical Characteristics of Barium Cadmium Formate Crystals

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Physical Characteristics of Barium Cadmium Formate Crystals

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