Pyrochlore- and hollandite-type minerals were extensively investigated as the nuclear waste-forms, showing the unique properties on thermal and chemical stabilities and irradiation resistance. In the past decade, our group methodically studied the crystal structure and chemistry of pyrochlore- and holladnite-type natural minerals and their synthesized compounds. According to X-ray diffraction analysis of fourteen synthesized rare-earth pyrochlore(Ree_2B_2O_7, B=Ti, Zr), both Ree_2Ti_2O_7 and Ree_2Zr_2O_7 sh...