A new orthorhombic phase of previously reported orthorhombic Na2GdOPO4, sodium gadolinium oxyphosphate, was synthesized by solid state reactions starting with four different sets of chemicals at 1000 degrees C. The unit cell dimensions were calculated using its powder X-ray diffraction data and were found to be a = 14.709(6), b = 10.661(4) and c = 13.081(6) Angstrom and the space group is probably Pmm2 (No: 25). its monoclinic form was also obtained by further heating the orthorhombic phase at 1000 degrees C. The unit cell dimensions of the monoclinic form was found to be a = 14.719(5), b = 10.669(3), c = 13.091(5) Angstrom and beta = 92.274 degrees(2). Using the same procedure Na2LaOPO4 was also prepared the first time in this work through three sets of starting materials at 1000 degrees C. Na2LaOPO4 also crystallizes in the orthorhombic system with a = 13.657(5), b = 11.076(5), c = 6.730(3) Angstrom which seems to be isostructural with Na2GdOPO4 prepared before in our laboratory. The IR data of both Gd and La compounds agreed with the literature values. (C) 2000 Elsevier Science S.A. All rights reserved.