Brushite was synthesized by precipitation of calcium chloride (CaCl(2)) and sodium phosphate monobasic (Na(2)HPO(4)) dried in vacuum and monetite was obtained from this brushite by sonication with a frequency of 90kHz at 500W for 90min. Monetite itself was also transformed in Ca(H(2)PO(4))(2)·H(2)O, monocalcium phosphate monohydrate (MCPM), by sonication with a frequency of 90kHz at 500W for 60min followed by lyophilization. The MCPM was sonicated and lyophilized by three times more until reach over 240min, but any other phase transformation was observed. All these phase transformations were analyzed by X-ray diffraction (XRD) and infrared spectroscopy (FTIR). Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) indicated a grain size of about 200nm in all the samples. The morphology observed was a corn-flake-like grain for brushite, a pseudo-needle-like grains for monetite, and lamellar-like grains for MCPM.