A precursor vessel comprises a hafnium halide precursor. The hafnium halide precursor comprises less than 1 ppm of at least one impurity. The at least one impurity comprises at least one of a titanium contaminant, a chromium contaminant, an aluminum contaminant, an iron contaminant, or any combination thereof. Related systems and related methods are also provided, including, for example and without limitation, systems for delivery of vapor precursors, methods for purifying a precursor, and the like.