Thin films of a-/b- and c-axis oriented SrBi2Ta2O9 (SBT) were epitaxially grown on (110) MgO and (100) MgO substrates, respectively, by a rf magnetron sputtering deposition method. The orthorhombic SBT phase was confirmed by electron probe microanalysis and infrared reflectance spectra. The oriented growth was proved by transmission electron microscopy together with x-ray diffraction. The orientation relationship of the a-/b-axis oriented film with the substrates was determined to be SBT[001]//MgO[001] and SBT[010]//MgO[1 (1) over bar 0](SBT[100]//MgO[1 (1) over bar 0]) from electron diffraction patterns. (C) 1999 American Institute of Physics. [S0003-6951(99)02544-9].