Powder X-ray diffraction measurements of La1-xYxAlO3 suggested that the space groups of x=0.3 and 0.9 samples are Pnma at room temperature and that a structural phase transition occurs from R-3c to Pnma above 200 K in x=0.1 sample. The unit cell volumes of x=0.1, 0.3, and 0.9 samples at 20 K are larger than the average one estimated from the volumes of LaAlO3 and YAlO3. The heat capacities of x=0.1 and 0.3 samples are larger than those of LaAlO3 in the range 3-20 K. On the other hand, the volumes of Y1-xLuxAlO3 (x=0.1, 0.3, and 0.5) at 20 K are close to the average one and the heat capacity increased as x is increased in the range 3-20 K.