Several samples of rare-earth oxides of perovskite structure were developed and investigated between 1.5 and 10 K. The measurements have shown. that these materials have large magnetic moments and most of them exhibit a magnetic phase transition below 4 K. The heat capacities of the samples have been measured with the adiabatic heat-pulse method. The dependence of the heat capacity on the preparation temperature of the samples has been studied. The results of the measurements are presented in this paper. The possibility of using these materials as regenerator materials in cryocoolers, e.g. pulse-tube refrigerators, is discussed.