The tungsten bronze type solid solution systems,Sr_(1-x)Ba_xNb_2O_6(SBN)and(K_yNa_(1-y))0.4(Sr-(1-x)Ba_x)0.8 Nb_2O_6(KNSBN),areimportant photorefractive materials with enormous potentialities.

• Sr_(1-x)Ba_xNb_2O_6(SBN)和(K_yNa_(1-y))0.；4(Sr_(1-x)Ba_x)_0