Effect of hydrostatic pressure on the incommensurate phase ofK2SeO4

A neutron scattering study of the effect of hydrostatic pressure on the incommensurate phase transformation in ${\mathrm{K}}_2$Se${\mathrm{O}}_4$ was performed in order to obtain information concerning the nature of the competing forces that give rise to a structural instability at a general wave vector. It was found that an increase in pressure lowers the transition temperature ($\frac{d{T}_i}{d{P}_i}=-6.5\mathrm{}$ K/kbar) and results in a smaller value of the initial incommensurate wave vector. The pressure dependence of the incommensurate to ferroelectric phase transition was also investigated ($\frac{d{T}_c}{d{P}_c}\simeq -9\mathrm{}$ K/kbar). The latter transition displays a distinct pressure hysteresis.