DTA-TG and XRD study on the reaction between ZrOCl2·8H2O and (NH4)2HPO4 for synthesis of ZrP2O7

Abstract

In this paper, we report results of thermoanalytical investigation on the reaction between ZrOCl 2 Á8H 2 O and (NH 4 ) 2 HPO 4 in molar ratio 1:2. Differential thermalthermogravimetric and X-ray diffraction analyses were performed in order to reveal the chemical transformations, which took place during heating of the individual compounds ZrOCl 2 Á8H 2 O, (NH 4 ) 2 HPO 4 and the mixture ZrOCl 2 Á8H 2 O:2(NH 4 ) 2 HPO 4 . It was shown that the transformations in the mixture below 160°C were connected with dehydration of ZrOCl 2 Á8H 2 O and interaction between the components of the mixture, which resulted in the formation of NH 4 Cl, NH 4 H 2 PO 4 and a mainly amorphous zirconium phase, most likely t-ZrO 2 . The zirconium component subsequently reacted with ammonium dihydrophosphate (below 200°C) or with dehydrated phosphate derivatives (above 200°C), which in both cases yielded an amorphous product. The interaction between the components of the mixture resulting in the formation of ZrP 2 O 7 was completed by its crystallisation at 610°C. Our study indicates an alternative low-temperature approach for the synthesis of the technologically important ZrP 2 O 7 material.

Structural and thermal transformations on high energy milling of natural apatite

“…This fact determinates the initial the TF0 as isomorphically substituted CAp and it is in conformity with the conditions of their formation. Appearance of a new band in the region of this doublet is assigned to CO 3 2-which substitutes F -along the hexagonal axis and in the channel structure of apatite (A1 and A2-type substitution) [15][16][17][18][19][20][21]. The mechanism of this type of substitution most probably contains the following steps-involving of CO 2 from air, partly decomposition of calcite, and relocation and migration of carbonate ions from tetrahedral positions of the phosphate ion [3].…”

Synthesis and homogeneity range of Yb8−xYxV2O17 in the Yb8V2O17–Y8V2O17 system

“…The DTA method for testing the thermal stability of the various phases forming in the multicomponent oxide systems was described, inter alia, in [30][31][32][33]. Selected samples were investigated also by means of an electron scanning microscope-SEM (JSM-6100, Jeol, Japan).…”

Heterovalent Zr4+-Cu2+ substitution in zirconium pyrophosphate: From theoretical models to synthesis and utilization

“…Therefore this interaction (including dehydration) and the following decomposition of NH 4 Cl did not became dominating features on the thermoanalytical curves, as it was observed for the mixtures with high content of ZrOCl 2 ·8H 2 O (x = 0.1). Instead, the general features of the DTA-TG curves are very similar to the characteristic thermal behaviour of (NH 4 ) 2 HPO 4 and its mixtures: release of ammonia around 200 • C and condensation of phosphate anion between 350 and 400 • C are usually dominating processes [20,43,44]. Thus, common features which were observed for the samples of both models are the following:…”

“…Alternatively, zirconium(IV) oxychloride octahydrate (ZrOCl 2 ·8H 2 O) can be also considered as a highly reactive source of zirconium in solid state reaction because its decomposition initially leads to the formation of t-ZrO 2 [42]. Results of thermoanalytical study of the reaction between ZrOCl 2 ·8H 2 O and (NH 4 ) 2 HPO 4 in molar ratio 1:2 are reported in our previous paper [20]. The proposed synthesis approach resulted in the formation of pure crystalline phase of ZrP 2 O 7 at 650 • C. Thus, for the synthesis of the solid solutions on basis of ZrP 2 O 7 we have employed similar approach.…”

“…In our previous study [20], we have already reported results of thermoanalytical investigation on the reaction between ZrOCl 2 ·8H 2 O and (NH 4 ) 2 HPO 4 (in molar ratio 1:2) during calcination. According to our results, this reaction is accomplished by the formation of pure phase of ZrP 2 O 7 at a comparatively low temperature, i.e.…”