Bi substituted YIG ceramics isolator for optical communication

We have succeeded in synthesizing transparent (BixY3-x)Fe5O12 [x = 0–1.1] ceramics by reactive sintering method for the first time in the world. The transmission spectrum of Bi-doped YIG showed characteristics comparable to the Bi:Gd3Fe5O12 single crystal produced by LPE method. The obtained Bi:YIG ceramic was uniformly composed of grains around below 5 μm. Residual pores, secondary phases and grain boundary phases were not detected. The distribution of Bi, Y, and Fe in this material was extremely uniform for up to x = 0.4, but a rather high concentration of Bi at grain boundaries was detected by HR-TEM-EDS analysis for x = 0.8. The Faraday rotation angle linearly increased with the Bi content, and the Faraday rotation angle per atomic % of Bi was −31.2 deg./cm at 1550 nm, and this value was similar to the (Bi1.1Gd1.9)Fe5O12 single crystal produced by LPE method. In addition to LPE method which requires a seed substrate (Gd3Ga5O12) and a steep temperature gradient, it was demonstrated in this work that Bi-doped iron garnet can be synthesized by solid-state reactive sintering method, and also confirmed that the magneto-optical performance of the polycrystalline Bi:YIG ceramics was equivalent to single crystal.