Preparation, electrical, thermal and mechanical properties of near-stoichiometric lithium tantalate wafers

Near-stoichiometric lithium tantalate (NSLT) crystal wafers were prepared by a vapour transfer equilibrium (VTE) method. The electrical, thermal and mechanical properties of NSLT wafers were tested by the four-probe method, laser pulse thermal conductivity and Vickers hardness testing. It was found that with the increasing Li content in the crystal, the conductivity of NSLT wafer first decreases, then increases and then decreases once more. The maximum conductivity of 4.4 × 10 − 12 Ω −1 cm − 1 is measured when the Li content is 49.64%. By analysing the thermal and mechanical properties of NSLT wafers with different Li contents, it was observed that the thermal conductivity of NSLT wafers first increases and then decreases with gradually increasing Li content. The thermal conductivity reaches a maximum value of 4.6 W/(m K) when Li content is 49.75%. Vickers hardness decreases significantly with Li diffusion and then increases slowly. In this study, wafers with Li content between 49.64 and 49.75% have more excellent electrical and thermal properties, but the Vickers hardness of the wafer does not reach its ideal value. Here, it is considered that there is an optimal Li content in the application of NSLT crystals in electronics, heat and mechanics, which is not necessarily the closest to the stoichiometric ratio.