Abstract
The Raman spectra of Bi2−nL,nTi4Ol1at hydrostatic pressure and various temperature have been measured by a Diamond Anvil Cell (DAC), with a temperature equipment and a Ramalog system. The results show that the pressure dependence of the phase transition temperature follows Samara's rule and the phase transition is driven by the soft optical mode. Nature of non-zero value of the soft mode frequency at phase transition point has been first discussed.