Absorption spectroscopy and energy levels of rare earth impurity centres in Sr_x Ba_1–xNb₂O₆ crystals

Abstract

The absorption spectra of Ce3+, Nd3+, Eu3+, Tb3+, Er3+, Tm3+ and Yb3+ rare earth (RE) impurity ions incorporated in Srx Ba1–x Nb2O6 (SBN) crystals were studied in a wide spectral range from the visible to the mid‐infrared. On the basis of the analysis of the Ce3+ absorption line shapes and their polarization properties the conclusion was drawn about the incorporation of multiple Ce3+ centres mostly in the position A1 of the crystal lattice of SBN. From the observed temperature dependence of the Ce3+ absorption line broadening the electron coupling strength (160 cm–1) and effective phonon energy (300 cm–1) were determined. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Local environments and transport properties of heavily doped strontium barium niobates Sr0.5Ba0.5Nb2O6

“…The Seebeck coefficient reaches 281 V/ K at 930 K [5] , [8] while a three orders of magnitude increase of the electrical conductivity has been related to a reduction of the binding energy of oxygen vacancies when approaching the ferroelectric transition [9]. The charge transport depends on the reduction temperature and reduction degree, and a polaronic mechanism has been reported by several authors [6,[52][53][54].…”

“…Doping is expected [55] , [56] to further decrease thermal conductivity, but is mainly investigated in hopes of achieving good values of electrical conductivity (σ) and Seebeck coefficient (S), which are generally too low. However, only doping of SBN materials at low levels (few %) has been investigated largely [8,15,22,23,28,35,36,38,39,53,[57][58][59][60][61][62][63][64], while it would be highly desirable to explore the feasibility and effectiveness of doping at high levels, when doping is expected to affect the whole band structure in addition to a simple injection of electrons or holes.…”