This paper investigates the influence of the microstructure of plasma-sprayed thermal barrier coatings on sintering with the aim to develop more sintering-resistant coatings. The influence of the microstructures on the layer properties as well as the change of the microstructure during thermal treatment at high temperature is investigated. The sintering behavior is examined with a dilatometer. The results showed that the amount of sintering increases with increasing porosity and decreasing segmentation cracks. The elastic modulus of the layer before and after thermal treatment is determined by bending tests at room temperature. It is observed that a significant increase in the modulus of elasticity is associated with the duration of the high-temperature annealing. Paper includes a German-language abstract.