The effect of radiation damage on micro-mechanical properties of Bi4Ge3O12 single crystal

In this work, bismuth germanate (Bi4Ge3O12 or BGO) crystals were grown by vertical Bridgmen method, and the micro-mechanical properties of BGO crystal before and after ultraviolet irradiation (UV-irradiation) were systematically investigated using micro-indentation technique and discussed combining with the optical properties. The results suggested that BGO crystal exhibited significant changes of the optical properties before and after UV-irradiation, showing obvious radiation damage. After UV-irradiation, the colorless and transparent BGO crystal turned to be light brown, and the optical transmittance at 350 and 480 nm were cut down about 12.6% and 5.83%, respectively. The peak of thermoluminescence curve of the irradiated BGO crystal was much stronger than that of the non-irradiated sample, implying the apparent increase of the concentration of color centers. Furthermore, it was found that the Vickers' micro-hardness Hv increased about 5.44% from 533 to 562 kg mm−1/2, the fracture toughness Kc decreased about 6.53% from 0.674 to 0.630 MPa m1/2, which showed that BGO crystal became little “hard and brittle” as a result of radiation damage.