Photoinduced absorption and anomalous dichroism in NaCa₂Mn₂V₃O₁₂ garnet as an evidence for the formation of oxygen holes dynamics

It is shown that long-lived photoinduced dichroism in garnets is caused by photoproduced charges with anisotropic structure, keeping long memory of the pumping light polarization, while photoinduced absorption is due to all photoproduced charges irrespective of their intrinsic structure. The charges with anisotropic structure are identified as two-center oxygen holes. The formation of an oxygen hole is preceded by the excitation of a charge-transfer state with electron partially transferred to a cation C (V⁵⁺ for NaCa₂Mn₂V₃O₁₂ garnet) from an adjacent oxygen anion. To turn this excited state into a free hole state requires some time τhole during which the hole axis can be reoriented resulting in a diminution of dichroism. The time τhole shortens with increasing ionization potential of the cation C (very high for V⁵⁺). Such a mechanism explains qualitatively a set of unusual experimental facts, in particular, a very strong dichroism observed just in the NaCa₂Mn₂V₃O₁₂ garnet, where photoinduced changes of all optical properties disappear after switching off of the irradiation significantly faster than those in other garnets examined

Influence of doping methods and Nd³⁺ concentration on the formation of dipole and activator centers in PbMoO₄:Nd³⁺ and PbWO₄:Nd³⁺ crystals

Equivalent curcuits were used to study peculiarities of polarization processes in PbMoO₄:Nd³⁺ and PbWO₄:Nd³⁺ crystals depending on a doping method. The method of doping was found to influence the formation of dipoles defining the polarization processes in these crystals. On the base of the obtained data the models of activator centers in PbMoO₄:Nd³⁺ and PbWO₄:Nd³⁺ crystals are proposed

Morphology of oxide single crystals grown by Czochralski technique at low axial gradients

Technological factors causing non-cylindrical morphology of LiNbO₃, PbWO₄ and Li₆Gd(ВО₃)₃ single crystals grown by Czochralski technique have been considered

Characteristics of lasers based on binary vanadate and orthoborate single crystals with disordered structure

Characteristics of lasers based on the binary orthovanadates Ca₁₀Li(VO₄)₇:Nd, Ca₉La(VO₄)₇:Nd and the orthoborates Ca₃RE₂(BO₃)₄:Nd (RE = Y, Gd) crystals with disordered structure were investigated. For Ca₃Y₂(BO₃)₄:Nd crystals laser oscillations was observed for the first time. The obtained slope efficiencies of vanadate-based lasers are comparable with the one of the lamp-pumped laser based on commercial Y₃Al₅O₁₂:Nd crystal. The optical breakdown threshold of binary vanadate crystals is higher than that of the orthoborate crystals. For Ca₁₀Li(VO₄)₇:Nd and Ca₉La(VO₄)₇:Nd crystals the values of optical breakdown threshold are approximately the same - 80 J/cm². The optical breakdown thresholds of Ca₃Y₂(BO₃)₄:Nd and Ca₃Gd₂(BO₃)₄:Nd crystals is approximately twice as low

Quantitative evaluation of microimpurity content in lead tungstate initial raw material and scintillation single crystals

The results of impurity composition determination in lead tungstate raw material and in the scintillation single crystals at various stages of the technological process are presented. Iron content in the samples was determined by extraction photometry after the double-stage sample breakdown. AI, Bi, Сг, Сu, Mg, Mn, Mо, Ni, Si, Sn, and Ti were determined by atomic emission spectroscopy under arc excitation. The revealed differences in the concentration levels of the above-listed impurities in colored and colorless crystals have been demonstrated to be insufficient for make any substantial effect on the crystal light absorption. These differences have been supposed to be caused by formation of intrinsic impurities in the course of the raw material solid-phase synthesis.Наведено результати визначення домiшкового вмiсту у сировинi та монокристалах вольфрамату свинцю на рiзних стадiях технологiчного процесу. Вмiст залiза визначали екстракцiйно-фотометричним методом з двостадiйним розкриттям зразкiв. Вмiст AI, Bi, Сг, Сu, Mg, Mn, Mо, Ni, Si, Sn, Ti визначали методом атомно-емiсiйної спектрометрiї з дуговим джерелом збудження. Показано, що рiзницi, що встановлено, на рiвнi вмiсту перелiчених домiшок у забарвлених та незабарвлених кристалах недостатньо для суттевого впливу на їх свiтопоглинання. Висловлено припущення, що вказанi вiдмiнностi обумовленi появою власних домiшок у процесi твердофазного синтезу сировини.Представлены результаты определения примесного состава сырья и монокристаллов вольфрамата свинца на разных стадиях технологического процесса. Содержание железа определяли экстракционно-фотометрическим методом с двухстадийным вскрытием образцов. Содержание AI, Bi, Сг, Сu, Mg, Mn, Mо, Ni, Si, Sn, Ti определяли методом атомно-эмиссионной спектрометрии с дуговым источником возбуждения. Показано, что установленные различия в уровне содержаний перечисленных примесей в окрашенных и неокрашенных кристаллах недостаточны для существенного влияния на их светопоглощение. Высказано предположение, что указанные различия обусловлены появлением собственных примесей в процессе твердофазного синтеза сырья

Growth and scintillation properties of NaLa(WO₄)₂ and NaLa(MoO₄)₂ single crystals

Pure and doped NaLa(WO₄)₂ and NaLa(MoO₄)₂ single crystals have been grown by the Czhochralski technique. The scintillation characteristics thereof have been determined and considered.Методом Чохральського вирощено чисті та активовані монокристали подвійного вольфрамату NaLa(WO₄)₂ та молібдату NaLa(MoO₄)₂. Визначено та проаналізовано їхні сцинтиляційні характеристики.Методом Чохральского выращены чистые и активированные монокристаллы вольфрамата NaLa(WO₄)₂ и молибдата NaLa(MoO₄)₂. Определены и проанализированы их сцинтилляционные характеристики

Growth and spectroscopy of new laser crystals Ca₁₀Yb₀.₃K₀.₁(VO₄)₇

Ca₁₀Yb₀.₃K₀.₁(VO₄)₇ single crystals have been grown for the first time. Absorption and luminescence spectra, luminescence decay kinetics of ²F ₅/₂ level for Yb³⁺ ion are investigated

Influence of processing conditions on the structure and properties of yttrium oxide ceramics

By means of "wet" chemistry method Y₂O₃ nanopowder was obtained and characterized by X-ray diffraction analysis and differential thermal analysis. Transparent samples of Y₂O₃ and Y₂O₃:Nd ceramics were produced by vacuum sintering. Granulometric and phase compositions, crystal structure, spectral-kinetic and mechanical properties of the ceramics were studied

Portable radiation monitoring system on the base of CdWO₄ scintillator

A portable high-sensitivity monitor for the detection of radioactive materials is developed and manufactured on the base of CdW0₄ scintillation crystal. The monitor has an independent power supply which provides continuous operation at least during 120 hours.Розроблено і виготовлено портативний високочутливий портал для виявлення радіоактивних матеріалів на базі сцинтиляційного кристала CdW0₄. Портал має власний блок живлення, який забезпечує його безперервну роботу протягом 120 годин.Разработан и изготовлен портативный высокочувствительный портал для обнаружения радиоактивных материалов на базе сцинтилляционного кристалла CdWO₄. Портал оснащен собственным источником питания, который обеспечивает его непрерывную работу в течение 120 часов