Abstract: On the basis of the physics gas phase method , the CdSe crystal with natural appearances was grown by the unconstrained quadratic phase vapor transport method , the size of which is about 6 mm ×7 mm ×2 mm.The microstructure , composition and morphology of the crystal were characterized by XRD , ICP-MS and SEM .The peak intensity of XRD diffraction is high without impurity peaks .The three natural appearances of CdSe crystal are (100), (002) and (110) planes, respectively, and the full width at half maximum ( FWHM ) of the rocking curves are small .The CdSe crystal grown by the unconstrained quadratic phase vapor transport method has less impurity content and higher infrared transmission .SEM observation demonstrates that the cleavage planes is stair-stepping and the stretching direction of the steps are uniform .All the results show that the CdSe crystal grown by the unconstrained quadratic phase vapor transport method has high purity ,crystalline quality and infrared transmission ,and the reason of natural appearances of CdSe crystal was analyzed by BFDH model .

Key words: On the basis of the physics gas phase method , the CdSe crystal with natural appearances was grown by the unconstrained quadratic phase vapor transport method , the size of which is about 6 mm ×7 mm ×2 mm.The microstructure , composition and morphology of the crystal were characterized by XRD , ICP-MS and SEM .The peak intensity of XRD diffraction is high without impurity peaks .The three natural appearances of CdSe crystal are (100), (002) and (110) planes, respectively, and the full width at half maximum ( FWHM ) of the rocking curves are small .The CdSe crystal grown by the unconstrained quadratic phase vapor transport method has less impurity content and higher infrared transmission .SEM observation demonstrates that the cleavage planes is stair-stepping and the stretching direction of the steps are uniform .All the results show that the CdSe crystal grown by the unconstrained quadratic phase vapor transport method has high purity ,crystalline quality and infrared transmission ,and the reason of natural appearances of CdSe crystal was analyzed by BFDH model .