Phase diagram of ${\mathrm{KH}}_2$(${\mathrm{P}}_{1\mathrm{-}\mathit{x}}$${\mathrm{As}}_{\mathit{x}}$)${\mathrm{O}}_4$ mixed crystals

The phase transitions of ${\mathrm{KH}}_2$(${\mathrm{P}}_{1\mathrm{-}\mathit{x}}$${\mathrm{As}}_{\mathit{x}}$)${\mathrm{O}}_4$ solid solutions between ferroelectric ${\mathrm{KH}}_2$${\mathrm{PO}}_4$ and its isomorphous ferroelectric ${\mathrm{KH}}_2$${\mathrm{AsO}}_4$ have been studied by dielectric measurements over the whole concentration range 0≤x≤1. The transition temperature versus x, ${\mathit{T}}_{\mathit{c}}$(x), showed a large bowing downwards. The ferroelectricity below ${\mathit{T}}_{\mathit{c}}$ was confirmed by a D-E hysteresis loop, which became weakened near x=0.68.