COMPARATIVE ANALYSIS OF THE PROPERTIES OF SODIUM NIOBATE AND SODIUM - LITHIUM NIOBATE CERAMICS

Авторами исследовано влияние температуры синтеза ниобата натрия, на состояние поляризации в образцах керамики чистого ниобата натрия и модифицированного литием. Проведено сравнительное исследование структуры и пироэлектрических свойств полученных образцов. Показано, что введение в качестве модификатора лития приводит к существенному изменению структуры в глубине образцов керамики на основе ниобата натрия. Если в глубине образцов чистого ни ниобата натрия, как и на поверхности, различаются отдельные зерна, то центральная часть керамики ниобата натрия-лития представляет собой сплошной массив, в котором отдельные зерна не наблюдаются. Во всех образцах, кроме чистого ниобата натрия, синтезированного двойным синтезом (первый при 650 °C, второй при 700 °C), установлено существование градиента поляризации по толщине образцов, направленного от стороны, соответствующей положительному концу вектора поляризации к стороне, соответствующей отрицательному концу вектора поляризации. The authors studied the effect of the temperature of sodium niobate synthesis on the state of polarization in ceramic samples of pure sodium niobate and modified with lithium. A comparative study of the structure and pyroelectric properties of the obtained samples has been carried out. It is shown that the introduction of lithium as a modifier leads to a significant change in the structure in the depth of ceramic samples based on sodium niobate. If in the depth of the pure sodium niobate samples, as well as on the surface, there are individual grains, then the central part of the sodium niobate-lithium niobate ceramics is a continuous mass in which individual grains are not observed. In all samples, except for pure sodium niobate, which was synthesized by double synthesis (the first at 650 °C, the second at 700 °C), the existence of a polarization gradient along the thickness of the samples was established. The gradient is directed from the side corresponding to the positive end of the polarization vector to the side corresponding to the negative end of the polarization vector.

Design and modeling of multi-operation bit-manipulator logic circuit using lithium niobate waveguides

In this work, a high-performance multioperation bit-manipulator is presented. The presented electro-optical design can perform several bit-manipulations such as bidirectional bit-shifting, bit-rotation, multiply-by-2 and divide-by-2, and sequence designing operation. The technique relies on the electrooptic principle in lithium niobate. Lithium niobate-based waveguides have been used to design Mach–Zehnder interferometer, which is the fundamental optical switching element of the whole model. Extinction ratio, contrast ratio, and insertion loss values computed for the simulated results are 29.16 dB, 29.48 dB, and 0.77 dB, respectively.

Formation of self-assembled nanodomain structures in single crystals of uniaxial ferroelectrics lithium niobate, lithium tantalate and strontium–barium niobate

The formation and evolution of the self-assembled nanodomain structures during polarization reversal have been comparatively analyzed in single crystals of various uniaxial ferroelectrics: LiNbO 3 (LN), LiTaO 3 (LT) and Sr x Ba 1-x Nb 2 O 6 (SBN). Several experimental methods have been used for visualization of the micro- and nanodomain patterns. The static domain images have been obtained by optical microscopy and piezoresponse force microscopy. The Raman confocal microscopy allowed us to obtain the domain images in the bulk. The equilibrium slow switching with effective screening resulted in growth of polygon-shaped micro-domains: hexagons in LN, triangles in LT and squares in SBN, which corresponds to crystal symmetry. Switching in nonequilibrium conditions (noneffective screening of depolarization field) brings to appearance of similar nanodomain structures in all studied crystals as a result of different processes: (1) formation of nanodomain ensembles, (2) discrete switching, (3) incomplete merging and (4) spontaneous backswitching.