Microhardness of lithium niobate tantalate LiNb1-xTaxO3 solid solutions crystals

Growth of solid solutions of intermediate compositions LiNb1-xTaxO3 crystals allows you to adjust the physical parameters of the material and obtain crystals with the required properties, which is why obtaining such crystals and studying their properties taking into account anisotropy is an urgent task. Crystals of solid solutions of lithium niobate tantalate LiNb1-xTaxO3 of LiNb0.88Ta0.12O3 and LiNb0.93Ta0.07O3 compositions were grown in the work. Polished samples oriented in a standard installation were prepared from these crystals. The samples were subjected to monodomenization. The polarity of the piezoactive faces has been determined. By optical microscopy in transmitted light, patterns in the form of a sponge-like structure were observed on all samples of Z-cuts, patterns in the form of vertical regions parallel to the optical axis (Z-axis) were observed on samples of X- and Y-cuts. Taking into account anisotropy and polarity, measurements of the mechanical characteristics of the samples at a load of 25 gs were carried out: the microhardness of the samples according to Vickers HV calculated on the Mohs scale HM and the brittleness score Zx. According to the obtained data, the parameters of the «viscosity» S according to the Palmquist method and the degree of ionic bonds are calculated. The effect of the Nb : Ta ratio on the microhardness of Z-cuts is ambiguous, this may be due to the significant heterogeneity of such samples. In the case of X-cut samples, the results of microhardness measurements are close and within the error limits of the method. In the case of Y-cuts, there is a significant difference in the values of microhardness and brittleness of Y«+» and Y«–» sections, while the microhardness of the sample with a higher Nb content is higher.