Abstract: Submicrometer-sized, spherical vaterite particles were synthesized by solid-state reaction at room temperature in the presence of poly(acrylic acid)(PAA).The obtained products were characterized by XRD, IRand SEM.It was revealed that with increasing PAA amount, the crystal polymorph of CaCO₃particles varied gradually from pure calcite through a mixture of calcite and vaterite to pure vaterite, and the particle size decreased generally.It was proposed that in solid-state reaction, PAAinduced the formation of vaterite and the phase transformation from vaterite to calcite was prevented completely due to the absence of H₂O, resulting in the formation of pure vaterite particles.

Key words: Solid-state reaction at room temperature, CaCO₃particles, Vaterite, Poly(acrylic acid), Crystal polymorph control