Formation of a bidomain structure in lithium niobate wafers for beta-voltaic alternators

The possibility of increasing the efficiency of a beta-voltaic generator due to using a single-crystal bimorph element made of lithium niobate as a piezoelectric converter. The known beta voltaic alternators consist of a piezoelectric cantilever and a source of β-electrons. The cantilever represents a resilient member made, for example, of silicon, on which a piezoelectric element made of PZT piezoceramics is mounted. It is proposed to replace the silicon cantilever structure with a piezoelectric element by a uniform cantilever that represents a thin wafer made of a bidomain single-crystal lithium niobate. Due to this, the efficiency of the mechanical oscillation conversion into electrical power, the system Q-factor, and the stability of the operating parameters simultaneously increase; and the operation temperature range also significantly increases (by several hundred degrees). The solution of the main problem—the formation of a bidomain structure in a thin wafer of lithium niobate—is considered in detail. A method for the high-temperature annealing of samples in a nonuniform electric field is proposed. It is demonstrated that one can predict the domain structure based on the developed model. Samples are obtained having the occurrence depth of the interdomain boundary ranging from 120 to 150 μm. At the same time, it is shown that the sharpness of the boundary depends on the potential difference between the striated electrodes of the technological cell and the external electrode. The method is efficient for manufacturing a bidomain structure in a wafer up to 300 μm thick.