The anhydrous hafnium nitrate is volatile and has been reported as a CVD precursor for hafnium oxide films [[i]]
[i] R. C. Smith, T. Ma, N. Hoilien, L. Y. Tsung, M. J. Bevan, L. Colombo, J. Roberts, S. A. Campbell, W. L. Gladfelter, Adv. Mater. Opt. Electron., 2000, 10, 105.