A technological scheme has been developed for producing a uniform single-phase LiNbO3:Gd:B charge of a given composition. The charge is necessary to grow using the Czochralski method structurally and optically uniform lithium niobate (LN, LiNbO3) crystals co-doped simultaneously with gadolinium and boron. Studies of the optical and photorefractive properties of the resulting single crystal have been carried out by express assessment methods based on the number of scattering centers in the crystal volume photorefractive light scattering and laser conoscopy. Research indicates high optical quality of the crystal and its promising use as a nonlinear optical material.

The physicochemical characteristics, optical uniformity and photorefractive properties of a series of four LiNbO3:Er:Zn single crystals have been studied. Single crystals have been obtained by the Czochralski method. The erbium content in the crystals was 0.5 mol

Obtaining optical materials based on lithium niobate with controlled optical properties is an important task of modern materials science. To date the problem of obtaining heavily doped LiNbO3 crystals of optical quality with a macroscopically uniform impurity distribution has not been solved. In this work a comparative analysis of studies of the acoustic, optical and photorefractive properties of LiNbO3:Zn lithium niobate single crystals obtained by direct and homogeneous doping from melts with concentrations of 5,38-9,0 mol% Zn has been carried out. The following methods have been used: piezoacoustics, photoinduced light scattering and laser conoscopy. The values of the static piezoelectric modulus have been determined. According to these values, all crystals are single-domain. Studies of crystals have confirmed the absence of a photorefractive effect in them. It was established that LiNbO3:Zn crystals grown on the basis of the method of homogeneous doping with concentrations in the melt of 6,8-9,0 mol% Zn are characterized by the highest structural and optical uniformity. This is of interest for the technology of growing large zinc-doped lithium niobate crystals by the Czochralski method.

На основе метода гомогенного легирования из прекурсора Nb 2 O 5 :4.5 мол. % Zn и карбоната лития синтезирована однофазная шихта LiNbO 3 :4.1 мол. % Zn, из которой методом Чохральского выращены кристаллы ниобата лития. На основании результатов экспресс-оценки оптического качества кристаллов и рассчитанных значений пьезомодуля d 333 установлено, что исследуемые кристаллы характеризуются высоким оптическим качеством. Исследования кристаллов гомогенного и прямого легирования в области концентраций примеси 4.02–5.38 мол. % Zn методами фотоиндуцированного рассеяния света и лазерной коноскопии подтвердили их высокую оптическую однородность и стойкость к лазерному повреждению, фоторефрактивный отклик в кристаллах полностью отсутствовал. Полученные результаты могут быть использованы при выращивании крупногабаритных кристаллов LiNbO 3 :Zn, характеризующихся низкими значениями коэрцитивного поля и представляющих особый интерес для создания преобразователей лазерного излучения на периодически поляризованных структурах.

Using homogeneous doping, a Nb2O5:4.5 mol

A technologically feasible process has been proposed for the preparation of a LiNbO3:Mg,B growth charge from a Li2CO3 + Nb2O5 + MgO + H3BO3 mixture. Using such a growth charge, we have grown LiNbO3:Mg,B crystals with a highly uniform dopant distribution. High-speed evaluation of optical homogeneity has shown that the LiNbO3:Mg,B crystals have high optical quality. Using amplitude–frequency response and d333 piezoelectric modulus measurements, we have demonstrated a high degree of unipolarity of the LiNbO3:Mg,B crystals. The optical damage resistance and homogeneity of the LiNbO3:Mg,B crystals have been assessed using photoinduced light scattering and laser conoscopy. The results suggest that LiNbO3:Mg,B crystals with a weak photorefractive effect can be regarded as a new optical material for laser light conversion.

This paper presents a comparative analysis of the magnesium dopant distribution in the melt–crystal system during Czochralski growth of LiNbO3:B:Mg lithium niobate single crystals from a melt via sequential dilution of the melt with a nominally pure LiNbO3 growth charge. In the growth process, we used granulated growth charges prepared by two procedures: using homogeneous doping of a Nb2O5:B:Mg + Li2CO3 precursor and by solid-state reaction in a Li2CO3 + Nb2O5 + H3BO3 + MgO mixture. It has been shown that, all other crystal growth conditions being the same, homogeneous doping allows more magnesium (by 25

A technologically feasible process has been proposed for the preparation of homogeneous single-phase magnesium–boron codoped lithium niobate growth charge. It has been used in Czochralski growth of LiNbO3:Mg,B lithium niobate single crystals with a highly uniform dopant distribution. The crystals have been shown to have optical quality. The results of this study are important for designing a process for the preparation of materials with a weak photorefractive effect to be used in nonlinear optics and other areas of science and technology.

This paper reports a process for the growth of zinc–erbium codoped lithium niobate single crystals using a growth charge synthesized from a Nb2O5:Zn:Er precursor and Li2CO3. Characterization of the LiNbO3:Zn:Er crystals by high-speed evaluation of the number of scattering centers, piezoacoustic measurements, photoinduced light scattering, and laser conoscopy has demonstrated that they have high optical quality. The proposed technological approaches are aimed at designing functional materials with fundamentally new characteristics for electronics, acoustoelectronics, and integrated, quantum, and laser optics.

Improved methods and devices for nondestructive control of the degree of unipolarity of large LiNbO(3)crystals are described. These methods are based on measurements of the static and dynamic piezoelectric characteristics of crystals and are applicable to other ferroelectric materials. These methods allow assessment of the degree of unipolarity and the relative volume of antiparallel domains in crystals.

— This paper reports a process for the growth of optically homogeneous lithium niobate single crystals containing boron as a dopant. A LiNbO 3 :B crystal has been grown by the Czochralski technique using a single-phase growth charge synthesized from a Nb 2 O 5 :B precursor and lithium carbonate. We have assessed the optical quality of the crystal by a high-speed method from the number of scattering centers, evaluated its single-domain state by piezoacoustic measurements, and calculated its d 333 piezoelectric modulus component. The results demonstrate that the crystal has a high degree of optical uniformity and is single-domain. The proposed method for LiNbO 3 :B crystal growth can serve as a basis of a commercial-scale process for the preparation of doped lithium niobate single crystals for various engineering applications.

— In this paper, we describe improved methods for assessing the static and dynamic piezoelectric properties of lithium niobate crystals. The results can be used for evaluating results of conversion of large lithium niobate crystals to a single-domain state under mass production conditions. We present main calculated relationships for assessing the degree of unipolarity and the relative volume of antiparallel domains in large lithium niobate crystals. The described techniques are applicable to other piezoelectric materials as well.

A study of the temperature dependence of dielectric constant, conductivity, and piezoelectric modulus in the single-domain ate of LiNbO3 crystals modified by Zn admixture at threshold concentration is reported. Unipolarity of the LiNbO3:Zn crystals s observed to increase after treatment of brand-new samples by high-temperature electro-diffusion annealing and by subsequent high-temperature annealing of short-circuited samples. The observed effects are explained as a result of meta-stable residual domains collapsing at high temperature the collapse being assisted by disintegration of charged clusters stabilizing domain walls. The rise of unipolarity is accompanied by anomalies on the sigma(T) and epsilon(T) dependences and by a significant increase of the value of the piezo-modulus