The particle morphology, weight loss, and rheology of rhabdophane (LaPO4.nH(2)O) sols with either spherical or rod-shaped particles were characterized and compared. Some spherical particle sols were doped with aluminum. Particle size was characterized by light scattering and transmission electron microscopy (TEM). The additives that promote spherical particle formation also cause greater high temperature weight loss than similar rod-shaped particle sols. As expected, the shear-rate dependence of sol viscosity was much weaker for spherical particle sols. The viscosity for sols with both types of particles was modeled using particle aspect ratios and bound water layer thicknesses as variables. A bound water layer thickness of 3-5 nm was suggested by modeling, except in aluminum-doped sols, where a much larger thickness was suggested. Modeled aspect ratios were larger than those observed by TEM. Weakly bound agglomerates may be present in both types of sols.