I am trying to synthesise zirconia to use as a filler of pmma for nanocomposite, and I only obtained amorphous zirconium hydroxide, could it be useful for this purpose (calcination is not possible)?
Yes It can, However I assume you are making that nanocomposite for bio-medical applications. I highly recommend you to conduct a cytotoxicity test according to ISO10993 on your ceramic before starting any further study.