Preparation of Samarium Doped Calcium Hydrogen Phosphate and Study of Its Density and Thermal and Dielectric Characteristics

Samarium doped calcium hydrogen phosphate was synthesized as single crystal by room temperature solution growth technique, namely, silica gel technique. The kinetics of the growth parameters was studied with regard to variation of pH, dopant concentration, gel ageing, and upper reactant concentration. The optimum conditions for the growth of good quality single crystal were worked out. Single crystal X-ray diffraction analysis establishes that the crystal belongs to monoclinic system. The density observed by the flotation method is greater than the density of the reported pure calcium hydrogen phosphate thereby suggesting the incorporation of the dopant (Sm) ion into the lattice of host (CHP). Thermal analysis gave two sharp endothermic peaks which are due to partial dehydration and phase transition, respectively. Dielectric studies establish a shift in the Curie temperature from 355 to 370°C only at higher frequencies thereby suggesting the relaxational behavior of the material. 1. Introduction Rare earth phosphate crystals are interesting materials as they find wide technological applications on account of their ferroelectric, piezoelectric, optical, and other important properties whereas phosphoric acid serves as the base for the development of new class of materials. Calcium hydrogen phosphate dihydrate [CaHPO4 2H2O], also known as Brushite minerals, is a stable form of calcium phosphate [1]. Recent studies used it as a precursor to form apatite [Ca10(PO4)6(OH)2], an important bone forming mineral, as it contains 23% calcium in its anhydrous form. Brushite mineral has been found under various pathological conditions including kidney stones and some forms of arthritis [2, 3]. It was reported that the mineral deposits in the kidney contain various phases of calcium salts such as calcium oxalate and calcium phosphate [4]. Accordingly, it has been postulated that Brushite is a transient precursor for phases such as octacalcium phosphate and hydroxylapatite. Thus, calcium phosphate minerals are thought to be the initiator of stone formation in the kidney and/or bladder under favorable physiological environment. Brushite phase precipitates most readily in urine environments at pH less than 6.9, so it has been postulated that Brushite enables the nucleation of calcium oxalate monohydrate (COM), the major component of kidney stones [5]. Recently in 2012 investigations of kidney stones obtained from some patients of India showed the concentration of ten elements, namely, Ca, Na, K, Mn, Co, Cr, Zn, Br, Sm, and Cl [6] in the exploratory phase and a positive