Crystal structure and optical absorption properties of Er and Yb doped InTaO4 and InTaO4-yNy as photocatalysts under visible light

•Er3+ substitution at In3+ sites in the InTaO4 lattice expands light absorption.•In1-xErxTaO4 shows rich absorbance spectra in the visible (400–800 nm) region.•One sub-band gap at about 2.9–3.05 eV, associated to the In:5p-O:2p transitions.•When Er and Yb replace In atoms new states are introduced into the gap.•The localized character of the 4f electrons, does not modify the gap energy.