Pyroelectric detection of high-order commensurate phases with a narrow range of stability in betaine calcium chloride dihydrate

Betaine calcium chloride dihydrate exhibits a sequence of structural transitions from a $\mathrm{Pnma}$ phase to different commensurate or incommensurate phases modulated along the c axis. By measurements of the pyroelectric effect we have obtained the first experimental evidence of the existence of three new intermediate high-order commensurate phases, in agreement with recent theoretical predictions. The effect of a dc-bias electric field in the temperature range of stability of these phases is also reported.