Spectroscopic studies of SiO2–AlPO4 solid solutions

doi:10.1016/S0924-2031(98)00083-6

Vibrational Spectroscopy

Volume 19, Issue 2, April 1999, Pages 419-423

https://doi.org/10.1016/S0924-2031(98)00083-6 Get rights and content

Abstract

Middle infrared (MIR) spectra of a series of samples representing SiO₂–AlPO₄ system containing 100–75 mole% SiO₂ and 0–25 mole% AlPO₄ have been presented. They have been compared with the spectra of physical SiO₂ and AlPO₄ mixtures of the same compositions. Decomposition of the spectra has been carried out according to the mathematical self-deconvolution method using the minimization of the number of bands rule. Analysis of MIR spectra allows for identification of solid solutions in SiO₂–AlPO₄ system. It has been concluded that there exists a solid solution of AlPO₄ in SiO₂ up to 25 mole% of AlPO₄. For the SiO₂–AlPO₄ system, determination of solid solutions based on IR spectra is much simpler when compared to the procedure involving X-ray diffraction data. In contrast with IR spectra, diffraction patterns corresponding to different SiO₂ and AlPO₄ types are almost identical.

Introduction

Aluminium orthophosphate (AlPO₄) is isostructural with silica and has SiO₂-analogous polymorphic forms: berlinite (quartz structure), phosphotridymite and phosphocristobalite. Owing to structural similarity of AlPO₄ and SiO₂ one can expect that they should form solid solutions. There are, however, controversial opinions in the literature concerning this topic. According to Robinson and McMartney [1]a SiO₂–AlPO₄ solid solution does not exist. Kobayashi [2]reports the existence of a solid solution independent of concentration of the components, whereas Horn and Hummel [3]claim that the solid solution exists over a limited concentration range. Such different opinions are caused mainly by the fact that X-ray diffraction patterns of analogous SiO₂ and AlPO₄ polymorphic forms are practically identical and it is very difficult to observe shifts in the peak's positions or their splitting.

The aim of the present studies was to clarify whether the solid SiO₂–AlPO₄ solution exists and—if so—to determine the concentration range of its existence. In our previous work [4]an attempt to interpret X-ray diffraction patterns of a series of samples containing 100–75 mole% of SiO₂ and 0–25 mole% of AlPO₄, respectively has been undertaken. X-ray diffraction measurements carried out using an internal standard required a very precise adjustment of the diffractometer and were time-consuming. Very complicated computer-assisted calculations, based on the results made it possible to determine the unit cell parameters, were carried out. It was found that the solid SiO₂–AlPO₄ solutions exist up to the 20% mole of AlPO₄. The present work shows that the existence of solid AlPO₄–SiO₂ solutions can be proved using IR spectroscopic measurements and that this is a simpler procedure than interpretation of X-ray diffraction patterns.

Section snippets

Experimental

Materials containing from 100 to 75 mole% of SiO₂ and from 0 to 25 mole% of AlPO₄, respectively were prepared by the synthesis from pseudo-hydrosolution. Starting materials were: amorphous SiO₂, aluminium nitrate (Al(NO₃)₃·3H₂O) and orthophosphoric acid (H₃PO₄). Crystalline cristobalite-structure materials were obtained after long-term thermal treatment (400 h) at 1400°C in air. The samples were quenched in air (10°C/min). Crystalline powder of cristobalite and phosphocristobalite was prepared

Results and discussion

Structurally, AlPO₄ and SiO₂ are so similar that the standard X-ray diffraction measurements do not reveal the existence of their solid solution. MIR spectroscopy provides information on the short range ordering (individual chemical bonds), not the average structural information, as in case of XRD.

Interpretation of the IR spectra is rather complicated. Some of these difficulties can be excluded if the spectra are mathematically treated, i.e., the decomposition of complex bands envelopes into

Conclusions

MIR spectroscopy has proved the existence of solid SiO₂–AlPO₄ solutions containing up to 20 mole% of AlPO₄. The differences in the spectra of the analysed crystalline materials and physical AlPO₄–SiO₂ mixtures have been pointed out. SiO₂ and AlPO₄ have been shown to have different MIR spectra. In the solid solutions there exist two types of Si–O bonds whose vibrations are located at 1119 cm⁻¹ (Si–O(P)) and 1095 cm⁻¹ (Si–O(Si)).

Acknowledgements

This work has been supported by the Polish Committee for Scientific Research (KBN) under grant no. 7 T08D 020 10.

References (9)

M Handke et al.
J. Mol. Struct.
(1994)
M Rokita et al.
J. Mol. Struct.
(1998)
J Wong
J. Non-Cryst. Sol.
(1976)
P Robinson et al.
J. Am. Cer. Soc.
(1964)

There are more references available in the full text version of this article.

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Spectroscopic studies of SiO2–AlPO4 solid solutions

Abstract

Introduction

Section snippets

Experimental

Results and discussion

Conclusions

Acknowledgements

J. Mol. Struct.

J. Mol. Struct.

J. Non-Cryst. Sol.

J. Am. Cer. Soc.

Spectroscopic studies of SiO₂–AlPO₄ solid solutions