Transparent amorphous and glass–ceramics waveguides in the system ZrF4–LaF3–ErF3–AlF3 (ZELA) have been fabricated by physical vapor deposition (PVD). The ceramming process was studied by means of X-ray diffraction and transmission electron microscopy for different deposition temperatures. With increasing deposition temperature, formation of LaxEr1−xF3 nanocrystals with x ∼ 0.3 was observed. The decay curves of the 4I13/2 level in the glass–ceramics with 14.5 mol% Er3+ gave evidence of the presence of erbium both in the amorphous matrix (τ = 8.6 ms) and in the crystal phase (τ = 2.2 ms). The decrease of lifetime was due to clustering of erbium incorporated in LaF3 crystal lattice. No significant increase of attenuation loss was detected after waveguide cerammization (1.3 dB/cm at 1304 nm).