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Crystal growth and characterization of ADP (N[H.sub.4][H.sub.2]P[O.sub.4]) & KDP ([K.sub.2][H.sub.2]P[O.sub.4]).

1. INTRODUCTION

Crystal growth from solution is a very important process used in many applications from the industry to laboratory (Alexandru ,1970). Ammonium di hydrogen phosphate (ADP) and potassium di hydrogen phosphate (KDP) having important applications and harmonic generation was solution grown by slow evaporation technique at room temperature.

2. CRYSTAL GROWTH

Separate crystals of ADP and KDP were grown by solution growth employing evaporation technique at room temperature 30[degrees]c after 15 to 22 days the spontaneously nucleated crystals were grown to optimal sizes ranging 10 x 8 x 6 [mm.sup.3] to 40 x 24 x 24 [mm.sup.3]. Crystals of pure ADP and KDP were grown solution growth technique solubility studies and ADP and KDP were studied (Brice ,1986). The solubility of ADP was found to be 33gm per 100 ml of the solvent (double distilled water) and KDP was found to be 28gm per 100ml of the solvent Srinivasan et al ,1995).

2.1 SOLUBILITY OF ADP ([NH.sub.4][H.sub.2]P[O.sub.4]) & KDP ([K.sub.2][H.sub.2]P[O.sub.4])

The solution ADP and KDP are prepared by dissolving the respective salts in double distilled water maintained at a constant temperature with continuous stirring on reaching saturation. The equilibrium concentration of the solute is determined by gravimetry (Courtens,1983).The temperature dependence of solubility of ADP at pH values 5 as shown in figure A similar data for KDP at pH values 5 are shown in figure B.

3. CHARACTERIZATION

3.1 Single crystal X-RAY diffraction

The powder samples were loaded in a Rigaku X-ray duffraction apparatus using Cuk * radiation having * = 1. 54 and analysed. X-ray diffraction studies were carried out with the grown crystals in powdered form. Results compared with JCPDS file number 37-1479 (ADP) and 35-0807 (KDP) where the prominent peaks of the reported values coincided with the investigated patterns (Kurtz and Perry ,1968).

The XRD pattern of ADP fig (C) and KDP fig (D) had common three prominent peaks at (202) , (201), (204) another prominent peaks at (200), (112), (321). The cell parameters were found to be

A = 7.502 A[degrees] and c = 7.554 A[degrees] respectively. The cell volume (ADP) found to be 425.130A[degrees] and (KDP) 387.38 A[degrees]

[FIGURE A OMITTED]

[FIGURE B OMITTED]

[FIGURE C OMITTED]

3.2 FOURIER TRANSFORM INFRARED (FTIR)

Infrared spectroscopy is effectively used to identify the functional groups to determine the molecular structure of the compounds. The FT-IR spectrum was recorded using JASCO FT-IR 460 spectrometer by kbr pellet technique in the range 400-4000 [cm.sup.-1] and its shown in the figure (E) ADP and figure (F) KDP.

Infrared spectrometry involves examination of the twisting, bending, rotation and vibration modes of atoms in a molecule upon interaction with infrared radiation, portions of the incident radiation are absorb at the specific wave lengths.

[FIGURE D OMITTED]

[FIGURE E OMITTED]

[FIGURE F OMITTED]

3.3 MICRO HARDNESS STUDY

Micro hardness measurements are made using Leitz-wetzlar method miniload hardness tested fitted with a diamond pyramindal vicker's indenter (Mott ,1956). An indentation time 10 s were applied uniformily for loads 20 to 90gm. The hardness cut and polished lithium niabate sample Fig(G). Further higher loads showed that the hardness values sharply decreased and developed mild cracks on the pyramidal indentation edges. Below 90g the samples developed cracks due to the attainment of the threshold mechanical stress. Hardness values are estimated from the expression.

H = 1. 8544 x p/[d.sup.2] kg/[mm.sup.-2]

when p is the load applied an indenter in g and d the diagonal length of the impression in [micro]m. In this work the hardness of the pure ADP is higher than that of KDP crystal.

[FIGURE H OMITTED]

3.4 UV -VS- NIR SPECTRAL ANALYSIS

Spectral transmittance studied using shimadzu uv-1061uv-vis spectrophotometer with a single crystal of 4mm thickness in the range of 200-2000nm. The lower cut of wavelength 410nm. The transmittance percentage of ADP 45% compared to pure KDP 65%.

[FIGURE I OMITTED]

CONCLUSIONS

ADP, KDP crystals were grown by solution technique at room temperature. The changes in optical and qualitative properties were analyzed in comparison with KDP crystal. The transparency crystal of KDP was observed more than crystal of ADP.

ACKNOWLEDGEMENTS

The author thank to the referees for their invaluable comments and suggestions.

REFERENCES

[1.] Alexandru, H.V., 1971. J Crystal Growth 10:151, 1996. J. Crystal Growth 162.

[2.] Brice, J.C.1972. "The growth of Crystals from Liquids", North-Holland Publishing Company, Arnsterdam (1972).

[3.] Brice, J.C. 1986. "Crystal Growth Processes" Hursted Press, John Willey and Sons, New York (1986).

[4.] Courtens, E. 1983. Helv Phys Acta 56:705.

[5.] Kurtz, S.K and Perry, T.T. 1968. n characterization NLO crystals by novel SHG technique. J. Applied Phys., 39 : 3798

[6.] Mott, B.W. 1956. Micro indentation hardness Testing 81: Butterworth, London :p. 63.

[7.] Chernov, A.A., 1984. modern crystallography III-crystal growth. Springlar Verlag Co.

[8.] Loudise, R.A., 1970."The Growth of Single Crystals". Prentice-Hell Inc., New Jersay 1970.

[9.] Srinivasan, K., Anandkumar, S. and Ramasamy, P.1995. Mutual Solubility and Metartable Zone width of [NH.sub.4][H.sub.2]P[O.sub.4]- K[H.sub.2]P[O.sub.4] Mixed Solutions and Growth of Mixed Crystal. Growth 151, 226 (1995).

S. Kumararaman and J. Thomas Joseph Prakash *

Deptt. of Physics, Nehru Memorial College, Puthanampattai, Thuraiyur, (Tamil Nadu), India.

* Department of Physics, Thanthai Hans Roever College, Perambalur-621 212, India Email : armyjpr1@yahoo.co.in
Fig (G) : Microhardness Curve ADP, KDP

P Load d(ADP) d(KDP) [H.sub.v] ADP [H.sub.v] KDP

10
20 0.4202 0.4264 210 205
30 0.5147 0.5274 210 200
40 0.6015 0.6510 205 175
50 0.6809 0.7279 200 175
60 0.7755 0.8339 185 160
70 0.8870 0.9151 165 155
80 0.9783 1.0115 155 145
90 1.0728 1.1119 145 135
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Author:Kumararaman, S.; Prakash, J. Thomas Joseph
Publication:Bulletin of Pure & Applied Sciences-Physics
Date:Jan 1, 2006
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