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ESR study of transition metal ions diffused into sodium -alumina

University of British Columbia

ESR measurements are reported on the transition metal ions Mn²⁺ and Cu²⁺ diffused into sites in, and adjacent to, the conduction planes of sodium β"-alumina single crystals. The spin- Hamiltonian parameters obtained for Mn²⁺ are g[sub; ] = 2.0000(2), G[sub ┴] = 2.0019(2), A [sub; ] = -8.39(3) mT, A[sub ┴] = -8.33 mT and D = - 7.20(5) mT. The Mn²⁺ ions occupy the Al(3) sites adjacent to the conduction planes. The symmetry of the Cu²⁺ spectra place the Cu²⁺ ions at the mid-oxygen sites of the conduction planes. The complex spectra are a superposition of several different configurations of ions around this site which change as a function of the amount of Cu²⁺ diffused. The angular variations of the spectra can be divided into two main types: an anisotropic site symmetry with spin-Hamiltonian parameters g[sub; ] =11- 2.355, g[sub a ┴] , 2.087, A [sub; ] = 12.0 mT, A[sub a┴] 2.0 - 4.0 mT, and a more isotropic site symmetry with g [sub i; ] = 2.003, g[sub i┴] = 2.240, A[sub i; ] = 9.9 mT, A[sub i ┴] = 8.8 mT. These spectra are visible at liquid- helium temperatures. In addition an anisotropic, random-type spectrum is observed to replace the Cu²⁺ spectra as the temperature of annealed crystals is increased. This is attributed to the thermal motion of the Cu²⁺ ions due to their weak binding to the site. Suitable doping and annealing procedures to diffuse Mn²⁺ and Cu²⁺ into sodium β"-alumina are discussed and contrasted with the markedly different procedures in the case of the β structure.

Text

2010-05-31

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http://hdl.handle.net/2429/25258

Physics

University of British Columbia

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