Effect of Hydrostatic Pressure on the Phase Transitions of Langbeinite-Type Crystals

抄録

Effect of hydrostatic pressure up to 9 kbar has been studied by dielectric measurements on the six langbeinite-type crystals, Tl₂Cd₂(SO₄)₃, Rb₂Cd₂(SO₄)₃, K₂Zn₂(SO₄)₃, K₂Mn₂(SO₄)₃, Tl₂Mn₂(SO₄)₃ and (NH₄)₂Mn₂(SO₄)₃. The pressure-temperature phase diagrams were determined. In the former two crystals, Tl₂Cd₂(SO₄)₃ and Rb₂Cd₂(SO₄)₃, a new phase was found between the P1 and P2₁2₁2₁ phases at high pressure. In the crystal K₂Zn₂(SO₄)₃ another phase appeared between the P2₁3 and P2₁ phases, and the behavior is similar to that in (NH₄)₂Cd₂(SO₄)₃. The P2₁3→P2₁2₁2₁ transition temperature in K₂Mn₂(SO₄)₃ linearly rises with increasing pressure. The last two crystals, Tl₂Mn₂(SO₄)₃ and (NH₄)₂Mn₂(SO₄)₃ do not show any transition down to −196°C even under high pressure studied.