Infrared transmission spectra were measured systematically in polycrystallineLa1−xCaxMnO3−&dgr;and several systems substituted by other rare earth (RE) ions such asSm3+,Gd3+,Dy3+,etc., atLa3+sites or Fe ions at Mn sites but keeping the nominalMn4+/Mn3+≈3/7.Two strong absorption peaks located around 600 and 350cm−1,which are associated with internal phonon modes, i.e., stretching and bending modes ofMnO6octahedra, have been observed. Both of them are influenced by the concentrations of Ca and other RE ions substituting at the La and Mn sites. The details of the absorption peaks will be discussed on the basis of changes of the bond length of Mn-O and bond angle of Mn-O-Mn inMnO6octahedra. ©1997 American Institute of Physics.