Infrared and EPR studies of the red potassium molybdenum bronze K0.33MoO3

Infrared reflectance and electron-paramagnetic-resonance (EPR) of the red bronze K0.33MoO3are presented. The infrared measurements at 300 K indicated that red bronze K0.33MoO3is a semiconductor with very strong anisotropy in the range. The presence of three sharp lines at bout 900 cm−1for P⊥bis in fact due to the intramolecular oscillations of oxygen inside one octahedron. The phonon oscillators near 500 cm−1for P⊥band P∥bassociate with the modification of the effective charge. The EPR signals can be attributed to electrons localized in the isolated Mo5+paramagnetic center. The difference of relative intensities of the EPR lines in 300 K and 100 K is due to the electronic excitation. The inhomogeneous broadening of the resonance lines is due to a g-factor distribution arising from crystalline field and spin-orbit coupling.