Diffusion-related implications for langasite resonator operation

Oxygen and gallium diffusiveness in langasite were experimentally determined by analysis of diffusion profiles of /sup 18/O and /sup 71/Ga tracers by SIMS analysis as functions of temperature and doping. Strontium-enhanced diffusiveness and activation energies of /spl sim/1.2/spl plusmn/ 0.2 eV confirm the predominant role of oxygen vacancies in controlling the electrical conductivity of langasite at elevated temperature and oxygen partial pressure. The potential impact of high levels of porosity and the use of an oxygen primary ion beam on the accuracy of some of the data is discussed. The gallium diffusivity, with activation energy of 3.13 eV, was found to be more than two orders of magnitude lower than that of oxygen. Surface exchange measurements enabled estimation of gallium loss at elevated temperatures and oxygen partial pressure; the level is not believed to be of major concern for resonator performance.