The invention relates to a heat-insulating material, which is phase-stable particularly for high temperatures above 1150° C., especially above 1200° C., and which has a very good long-time stability. The heat-insulating material can exist in a number of phases of which at least one has the magnetoplumbite structure and stoichiometrically contains 0.1 to 10 mol % M12O3, 0.1 to 10 mol % Li2O and, as the remaining, M22O3 with incidental impurities. M1 is selected from the following elements: lanthanum, neodymium and gadolinium or mixtures thereof, and M2 is selected from the following elements: aluminum, gallium, iron or a mixture thereof. A particularly advantageous composition arises for this phase with the composition LaLiAl11O18.5 or LaLi0.5Al11.5O19. By using conventional methods, the heat-insulating material can be applied to the components subjected to a high level of thermal stress, for example, turbine blades. It is suited as a heat-insulating layer alone as well as for use in a composite material together with YSZ. The segmentation cracks regularly occurring in this heat-insulating material contribute significantly to a reduction in stresses between the heat-insulating layer and the coated component in the event of frequent alternating stresses.