Dielectric permittivity and Cr3+ impurity luminescence of Sr0.99M0.01TiO3 and SrTi0.99Mg0.01O3

Abstract

Dielectric permittivity epsilon' and a ``dielectric-related'' temperature shift of the R-emission line (E-2-->(4)A(2)) of the Cr3+ impurity centres were studied in SrTiO3 (STO), Sr0.99Mg0.01TiO3 (SMT) and SrTi0.99Mg0.01O3 (STM) ceramics. In STO, epsilon increases on cooling revealing a weak dispersion in the 100 Hz-1 MHz region at low temperatures. SMT shows nearly the same behaviour. In STM the low-frequency permittivity reveals a wide maximum at similar to36 K with pronounced relaxation-type dispersion. However, in the THz region no epsilon' (T) anomaly was found in all the materials under study. All the compositions studied-STO, SMT and STM demonstrate large ``dielectric-related'' temperature shift of Cr3+ R-emission line but this shift seems to be associated not only with TO1 soft mode but also with the relaxation process.