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Growth and characterization of struvite-Na crystals

Chetan K. Chauhan 1,2,3Mihirkumar J. Joshi 1

1. Saurashtra University, Department of Physics, Crystal Growth Laboratory, University Road, Rajkot 360005, India
2. Government Science College, Sector 15, Gandhinagar 382015, India
3. Knowledge Consortium of Gujarat, Dr Jivraj Mehta Bhavan, Gandhinagar 382010, India

Abstract

Sodium magnesium phosphate heptahydrate {NaMgPO4.7H2O}, also known as struvite-Na is the sodium analog to struvite. Among phosphate containing bio-minerals, struvite has attracted considerable attention, because of its common occurrence in a wide variety of environments. Struvite and family crystals were found as urinary calculi in humans and animals. Struvite-Na crystals were grown by single diffusion gel growth technique in silica hydro gel medium. Since the growth conditions play important role in the growth of crystals; in the present study, different growth parameters were used to grow struvite-Na crystals. Struvite-Na crystals with different morphologies having transparent to translucent diaphaneity were grown with different growth parameters. The phenomenon of Liesegang rings was also observed with some particular growth parameters. The crystals were characterized by powder XRD, FT-IR, thermal analysis and dielectric study. The powder XRD study confirmed the structural similarity of the grown struvite-Na crystals with struvite. It was found that struvite-Na crystallized in the orthorhombic Pmn21 space group with unit cell parameters as: a= 6.893 Å, b = 6.124 Å, c = 11.150 Å, α = β = γ = 90°. FTIR spectra of struvite-Na crystals revealed the presence of functional groups and confirmed the presence of water of hydration, P – O and PO43– ion and metal –oxygen vibrations. The TGA, DSC and DTA were carried out simultaneously. It was found that crystals started dehydrating and decomposing from 70°C and finally at 600°C temperature it became 63.9 % of the original weight and remained almost constant up to the end of analysis. The kinetic and thermodynamic parameters of dehydration / decomposition process were calculated. The variation of dielectric constant with frequency of applied field was studied in the range from 400 Hz to 100 kHz.

 

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Related papers

Presentation: Oral at 17th International Conference on Crystal Growth and Epitaxy - ICCGE-17, General Session 3, by Chetan K. Chauhan
See On-line Journal of 17th International Conference on Crystal Growth and Epitaxy - ICCGE-17

Submitted: 2013-03-28 17:40
Revised:   2013-03-29 13:47