90 . 95 . the phase transformation temperature of the natural cryptomelane was about 635 . 5 examined by tga and dta and the cryptomelane was changed to bixbyite at a higher temperature . these studies reveal the significant features of cryptomelane for the potential application in the environmental materials science K 3 . 37 % 4 . 17 %差热热重分析表明天然锰钾矿的结构热稳定性较好， 635 . 5时相转变为方铁锰矿。
