title: Structural changes of piezoelectric La3Ga5SiO14 induced by paramagnetic ions revealed by 71Ga multiple quantum magic angle spinning.
abstract: Experimental evidence that nuclear magnetic resonance (NMR) can detect structural changes of piezoelectric La(3)Ga(5)SiO(14) induced by dilute paramagnetic ions is presented. Gd(3+) and Eu(3+) cations have been incorporated into La(3)Ga(5)SiO(14) monocrystals. As expected, the line-width of the tetrahedral (29)Si magic angle spinning (MAS) NMR spectra as well as the inverse of the T(2) relaxation time of (71)Ga increases with the concentration of the paramagnetic ions. A surprising result is shown by (71)Ga multiple quantum (MQ) MAS NMR spectrum, which changes with the concentration of paramagnetic ions. The changes in the (71)Ga MQMAS spectra can be explained by a more ordonated distribution of Ga ions inside the oxygen tetrahedra. The (71)Ga MQMAS NMR spectra allow identification of the one octahedral and two tetrahedral Ga sites.
authors: Physics Faculty, Babes-Bolyai University, M. Kogalniceanu 1, Cluj-Napoca, Romania. fturcu@phys.ubbcluj.ro
authors: Flaviu
authors: F
authors: Turcu
authors: Simion
authors: S
authors: Simon
authors: Serban
authors: S
authors: Constantinescu
authors: Nicoleta
authors: N
authors: Grecu
authors: Dinu
authors: D
authors: Iuga