Terahertz time-domain spectroscopy and Raman scattering studies of incipient ferroelectric BaZrO₃

Abstract

We have studied an incipient ferroelectric BaZrO 3 single crystal with perovskite structure by terahertz time-domain and Raman scattering spectroscopies. The phonon-polariton dispersion relation of the lowfrequency infrared active TO1 and TO2 modes was studied from the real and imaginary parts of the complex dielectric constants at 8 K. The experimentally observed complex polariton dispersion relations are discussed by a damped harmonic oscillator model. First-order Raman active modes, forbidden in cubic Pm3m symmetry, have been observed in a BaZrO 3 single crystal, indicating the lowering of cubic symmetry.

Single crystal growth of BaZrO3 from the melt at 2700 °C using optical floating zone technique and growth prospects from BaB2O4 flux at 1350 °C

“…7). Crystals with large flat facets exhibit a spectrum that matches previously reported Raman spectra of BaZrO 3 [31,57,61] as well as the spectra shown in Fig. 4.…”

“…a) shows the Raman spectra of BZO1, BZO2 and BZO3 single crystals measured at ambient conditions in parallel scattering geometry. The spectra present a comparable signature, which are similar in their main features to the few spectra reported in the literature[31,57,61].…”

“…In spite of this, an intense Raman spectrum is usually observed [31,57,58], in a way that is reminiscent of other cubic perovskites (SrTiO 3 [59], KTaO 3 [60]). Second-order scattering processes involving combinations of two phonons usually explains it.…”

“…To the best of our knowledge, there are only a few publications available on the investigation of BaZrO 3 single crystal growth [31][32][33][34]. Single crystals are usually colored, small in size and their properties vary dramatically with the growth method.…”

Broadband Terahertz Spectroscopy of Phonon-Polariton Dispersion in Ferroelectrics

“…In this THz-TDS study, the real and imaginary parts of a dielectric constant were determined for a BZO single crystal at 8 K, and the imaginary part is shown in Figure 4a [22,23]. The dielectric constant was fitted by two damped harmonic oscillators to determine the mode frequency, dielectric strength, and the damping constant of two TO modes.…”