Thin Nb2O5-films were deposited on unheated glass, fused silica, and silicon substrates by reactive-low-voltage-high-current-ion-plating (RLVIP). Optical as well as mechanical film properties and their environmental stability are remarkably influenced by deposition parameters like e. g. arc current, deposition rate, gas composition, and total gas pressure. It was found out that an arc current around 50A, gas mixtures with high amount of oxygen, and a deposition rate around 0,3nm/s yielded the best results. Refractive indices were calculated from data obtained by spectrophotometric intensity measurements of the constrained amorphous and homogeneous films. Residual optical absorption in the film's high transmittance range was determined by photothermal deflection spectrometry. Mechanical film stress, for dense films always compressive, was measured by deformation of coated thin silicon discs. Typical obtained values are n550 = 2,39 - 2,40, k515 = 2×10-4, σ = -30MPa. Detailed information is presented in diagrams.