SEARCH FOR HIGH THERMAL-EXPANSION SUBSTRATES FOR MAGNETOOPTIC THICK-FILM GARNETS

The difference in thermal expansion between gallium garnet substrates and bismuth-doped rare-earth iron garnet epitaxial films results in a problem with breakage in thick film magneto-optic garnets. Forty diffe rent garnet composition were prepared by the ceramic sintering of powd ers, and sixteen of these were good enough to be examined by high-temp erature X-ray diffraction. None of the compositions displayed a signif icant increase in thermal expansion, though Ca3Mg1Zr1Ga3O12 was slight ly improved and had other favourable properties as a substrate materia l.