Synthesis, characterization of phosphate-based nano-mixtures of Fe and Ca and their thermal analysis

Abstract

• Nano-scale mixtures of Fe and Ca have been synthesized. • Mixtures show endothermic behaviour. • Explanation of negative specific heat capacity. • Both mixtures show semiconductor behaviour due to very less bandgap, E g = 0.64 eV • Sensible energy storage materials. • Thermal energy storage. In this work, synthesis of two novel and economic mixtures, 0.6 F e 3 ( P O 4 ) 2 · 8 H 2 O · CaHP O 4 · 1.5 CaS O 4 · Ca ( OH ) 2 (FPC4B) and 0.6 F e 3 ( P O 4 ) 2 · CaHP O 4 · 1.5 CaS O 4 · 2 H 2 O · Ca ( OH ) 2 (FPC4A) in nano-scale have been reported. A simple chemical route (wet) was followed for the synthesis. ICP-OES and CHNS (Quantitative) were used to deduce the compositions. Several analytical techniques such as SEM, TEM, FT-IR, XRD, TG-DTA, UV-VIS-NIR, DSC have been used for the characterization of the mixtures. Analyses results revealed the structural confirmation and respective crystallite size of FPC4A (59.84 nm) and FPC4B (69.73 nm). Various functional groups present in the mixture were confirmed by FT-IR. The thermal stability of both mixtures was investigated by TG-DTA. DSC curve revealed endothermic behaviour of mixtures indicating that both FPC4A and FPC4B can be exploited as sensible heat storage materials. E g (bandgap) of both mixtures were found to be 0.64eV with a refractive index of 3·48. SEM and TEM revealed the topographic constraint of both mixtures, which is rod-like in appearance.