We attempted synthesis of ZrO2 powders starting with the hydrolysis of ZrOCl2 in aqueous solution. The hydrolysis was performed by simply refluxing the solution at its boiling point, approximately 106 degrees Celcius. As a result, a white slurry was obtained. The resultant slurry was then centrifuged 10 - 24 hours later to obtain a white powder and a translucent supernatant. However, the ICP detection results of the supernatant indicated that the Zr content was 50% its original concentration before reaction started. Literatures regarding the reaction mechanism of ZrOCl2 hydrolysis pointed out that the reaction was 99% complete even after refluxing for 70 hours. So, is it possible that the hydrolysis product, ZrO(OH)2.xH2O dissolved in the acidic solution or slurry?
Dear Ming Zhang many thanks for your very interesting technical question. According to the CRC Handbook of Chemistry and Physics "zirconium hydroxide" ZrO(OH)2.xH2O is soluble in acids. It converts to ZrO2 upon heating. For some basic information about this compound please see the Wikipedia entry on zirconium(IV) hydroxide at https://en.wikipedia.org/wiki/Zirconium(IV)_hydroxide.
Please also have a look at the potentially useful research article cited below. In this paper the hydrolysis of ZrOCl2 and its final conversion to ZrO2 have been studied in detail:
Formation Mechanism of Hydrous Zirconia Particles Produced by Hydrolysis of ZrOCl2 Solutions: IV, Effects of ZrOCl2 Concentration and Reaction Temperature
Article Formation Mechanism of Hydrous Zirconia Particles Produced b...
(see attached pdf file)
I hope this helps. Good luck with your research and best wishes, Frank Edelmann
The aqueous solution of zirconium oxychloride (or zirconyl chloride) is acidic, as can be expected by considering the following equilibria:
(i) ZrOCl2 ↔ 2Cl- + (ZrO)2+
(ii) 2H2O + (ZrO)2+ ↔ ZrO(OH)+ + H3O+
The (acid) pH contributes favourably to stabilize the solution by avoiding the precipitation of zirconium oxide hydroxide, what could occur in slight alkaline solution:
(iii) ZrO(OH)+ + OH- ↔ ZrO(OH)2
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