IR Spectroscopy of PbZr1–xTixO3 Material: A Complementary Experimental/Ab Initio Calculations Approach of a Solid Solution

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The perovskites lead zirconium titanate, PbZr 1– x Ti x O 3 (0 < x < 1), known as PZT, are solid solutions widely exploited for their strong piezoelectric properties. The utmost technological importance of this class of materials led to considerable activity on piezoelectric films from the experimental and simulation side. In a solid solution like PZT, the distribution of Zr and Ti atoms has no long-range ordering. Thus, these materials are highly challenging to model theoretically but also to investigate experimentally. In this study, we combine infrared (IR) absorption spectroscopy, with a Density Functional Theory method adapted for the calculation of solid solutions. The complexity of PZT material is reproduced through a combination of 2 × 2 × 2 supercells. Using such combination procedure, we show here that ab initio calculations shed light on the interpretation of IR measured absorption spectra for thin films of 5, 10, 45, 90 nm with composition x = 0.75 in PbZr 1– x Ti x O 3, as well as for pure PbZrO 3 and PbTiO 3 . Furthermore, the simulation on the supercell structure was also performed for multiple compositions 0.5 ≤ x ≤ 1 in both tetragonal and cubic structures, allowing the understanding of the evolution of spectra with temperature (during the tetragonal to cubic phase transition) and with doping. This temperature study reveals the first experimental evidence of polar modes associated with the loss of spontaneous polarization in nanometer size PZT films, deposited on a silicon wafer. This combination of experimental and theoretical methods opens the way for the investigation of other solid solution materials.