Behavior of Impurities In and Cd in the LiNbO<SUB>3</SUB>-LiTaO<SUB>3</SUB> System

Abstract

The temperature dependences of the nuclear-electric-quadrupole frequency ω Q of 117 In and 111 Cd doped in ferroelectrics LiTaO 3 , Li 1−x In x/3 TaO 3 with x = 0.2, and Li 1−x Cd x/2 TaO 3 with x = 0.167, measured by the perturbed-angular-correlation technique, indicate that In behaves like Li; further, in a certain temperature range above the phase-transition temperature, a local system consisting of In (Li) and oxygen ions is very stable, by taking resonance structures, whereas Cd does not behave like Li, and a system consisting of Cd and oxygen ions does not take resonance structures, because the ionic size of Cd is large. It is considered that the resonance structures are due to a disordering of the oxygen ions, and that the order-disorder of oxygen ions is the driving mechanism for ferroelectric instability in the LiNbO 3 -LiTaO 3 system.

Perturbed-Angular-Correlation Studies on <SUP>111</SUP>Cd and <SUP>117</SUP>In in Pyrochlore Cd<SUB>2</SUB>Nb<SUB>2</SUB>O<SUB>7</SUB>

“…However, there are two non-equivalent oxygen sites, and the Nb ions are located within oxygen octahedra, whereas the Cd ions within scalenohedra (distorted cubes). ) polycrystalline samples containing 111m Cd and those containing 117 Cd were prepared with an identical method, 4,5) for LiNbO 3 and LiTaO 3 containing those Cd isotopes. The parent nuclei 111m Cd and 117 Cd were separately produced by irradiating enriched 110 CdO and 116 CdO, respectively, with thermal neutrons at the research reactor of Kyoto University.…”