Persistent spectral hole-burning of Eu³⁺ and Pr³⁺ in SrZr_{1 - x}Y_xO₃ crystals

Spectral hole-burning spectroscopy has been applied to proton conducting SrZrO₃:Y³⁺ single crystals. Transient and persistent hole-burning were observed in Eu³⁺ and Pr³⁺ doped SrZrO₃:Y³⁺ crystals, respectively. It is shown that holes can be burned by the optical pumping of the nuclear quadrupole levels of Eu³⁺. Since the spectral hole in Pr³⁺ doped crystals is observed only in H₂O- or D₂O-annealed samples, the hole-burning is caused by light-induced H⁺ or D⁺ motion which leads to persistent changes in the local crystal fields around the Pr³⁺ ions. The barrier height of proton (deuteron) tunneling transport is estimated in the Pr³⁺ doped system. The relationship between the long range proton conduction at high temperature and the local proton dynamics at low temperature is discussed.