Temperature-dependent Raman scattering study of tin modified PbZrO3 and PbHfO3 single crystals

Abstract

Using Raman scattering spectroscopy, the sequence of phase transitions in antiferroelectric PbZrO3 and PbHfO3 single crystals modified with Sn ions was investigated. As a consequence of the cation replacement (partial substitutions of Zr4+ or Hf4+ with isovalent Sn4+) the changes that took place in the different phase transition temperatures were reported. The phase transition temperatures for tin content of x=0.04 and 0.22 in PbZrO3 and x=0.025 in PbHfO3 were studied in the temperature range 300–600K. The modifications of the Raman spectra were observed in details in the vicinity of two structural phase transitions occurring in the crystals: antiferroelectric (AFE1)–antiferroelectric (AFE2) phase transition and antiferroelectric (AFE2)–paraelectric (PE) phase transition. The partial replacement of Zr or Hf ions with Sn ones does not change the nature of the phase transitions but widens the temperature range of intermediate phase and shifts AFE2–PE phase transition toward lower temperatures. It was shown that the presence of polar nanoregions (PNRs) in the high-temperature phase is the common feature of all three samples. The Raman measurements were supplemented by dielectric and differential scanning calorimetry (DSC) measurements. Excellent agreement for transition temperatures obtained by means of these three techniques suggests that Sn ions placed in octahedra are uniformly distributed in the material without introducing any mechanical stress.