X-Ray Study of High-Temperature Phase Transitions in KH₂PO₄

抄録

High-temperature phase transitions in KH₂PO₄ near 110°C and 180°C have been studied by X-ray diffraction. The extinction rule observed at 123°C is the same as that in the room-temperature phase. It is concluded that on heating through 187°C crystal system changes from tetragonal to monoclinic whose space group is P2₁ or P2₁⁄m. The lattice parameters at 195°C are given by a=7.47Å, b=7.33Å, c=14.49Å, α=β=90° and γ=92.2°.