In this article we report on a detailed study of the internal radioactive and chemical contamination of the Li6Eu(BO3)(3) scintillating crystal operated as a cryogenic scintillating bolometer over 359 h. The excellent discrimination power of the detector allows to distinguish effectively beta/gamma events from alpha events. Whilst a weak activity of daughter nuclides from U/Th chains at the level few mBq/kg was observed, this crystal was found to be significantly contaminated by Sm-147, an alpha-active nuclide, at the level of about 0.5 Bq/kg. The light yield for beta/gamma events was determined to be 7.4(6) keV/MeV. The light yield and quenching factor for alpha particles vary in the range of (0.5-1.2) keV/MeV and (0.07-0.17), respectively, due to energy dependence of the emitted scintillating light in the energy interval (2.0-7.0) MeV. The integral luminescence intensity of the Li6Eu(BO3)(3) crystal increases by more than four times only at low temperatures, below 80 K. Therefore, the Li6Eu(BO3)(3)-based cryogenic scintillating bolometers can be attractive detectors for direct neutron flux monitoring, to search for rare alpha decays or solar axions.

The Ca9RE(VO4)(7) (RE = La, Nd, Gd) and Ca10M(VO4)(7) (M = Li, Na, K) single crystals have been grown by the Czochralski method. The binary vanadates are isostructural to "whitlockite" mineral (rhombohedral symmetry, R3c space group). Their thermal conductivity has been investigated in the range 50K-300K parallel to the c axis. For Ca9Gd(VO4)(7) crystals, the thermal conductivity has been investigated in the range 300K-550K also. Additionally, for the Ca10M(VO4)(7) (M = Li, Na, K) crystals the heat capacity has been studied in the temperature range 80K-300K. The character of the temperature dependence of thermal conductivity is close to that of glasses. The possible reasons of the observed features of the thermal conductivity have been analyzed. Raman spectra of Ca10M(VO4)(7) (M = Li, Na, K) crystals have been measured and discussed. The spectral lines were broad and similar to polycrystalline or amorphous solids. These crystals are expected to be suitable for application as efficient nonlinear optic and laser materials.

The \(\hbox {Ca}_{9}\hbox {RE}(\hbox {VO}_{4})_{7}\) (RE \(=\) La, Nd, Gd) and \(\hbox {Ca}_{10}\hbox {M}(\hbox {VO}_{4})_{7}\) (M \(=\) Li, Na, K) single crystals have been grown by the Czochralski method. The binary vanadates are isostructural to “whitlockite” mineral (rhombohedral symmetry, R3c space group). Their thermal conductivity has been investigated in the range 50 K–300 K parallel to the c axis. For \(\hbox {Ca}_{9}\hbox {Gd}(\hbox {VO}_{4})_{7}\) crystals, the thermal conductivity has been investigated in the range 300 K–550 K also. Additionally, for the \(\hbox {Ca}_{10}\hbox {M}(\hbox {VO}_{4})_{7}\) (M \(=\) Li, Na, K) crystals the heat capacity has been studied in the temperature range 80 K–300 K. The character of the temperature dependence of thermal conductivity is close to that of glasses. The possible reasons of the observed features of the thermal conductivity have been analyzed. Raman spectra of \(\hbox {Ca}_{10}\hbox {M}(\hbox {VO}_{4})_{7}\) (M \(=\) Li, Na, K) crystals have been measured and discussed. The spectral lines were broad and similar to polycrystalline or amorphous solids. These crystals are expected to be suitable for application as efficient nonlinear optic and laser materials.

The Ca9Y(VO4)(7-x)(PO4)(x) (x = 0, 1, 3, 4) solid solution whitlockite-like single crystals have been grown by the Czochralski method from mixtures of single phase Ca9Y(VO4)(7) and Ca9Y(PO4)(7) starting materials produced by solid-state synthesis. Real compositions of solid solution crystals has been determined and analyzed. It is found that crystals with x = 0, 1, 4 exist with polar structure at room temperature, space group R3c. At least one of them, Ca9Y(VO4)(7), demonstrates ferroelectric behaviour with phase transition at 942 degrees C. Unlike the others, Ca9Y(VO4)(3)(PO4)(4) crystallizes in centrosymmetric whitlockite-like structure with space group R3c confirmed by single-crystal X-ray structure analysis. Similar to other whitlockite-family phosphates and vanadates, its crystal structure is described as a disordered structural version of usual whitlockites, corresponding to their high-temperature paraelectric phases. The transmission and luminescence spectra of solid solution crystals are reported, the hardness H-v and fracture toughness K-1c of solid solution single crystals are also determined. (C) 2017 Elsevier B.V. All rights reserved.

The archPbMoO4 scintillating crystal has been produced from archaeological lead for the first time. The advanced technique for deep purification of lead against chemical impurities was used resulting in 99.9995% purity level of final material. The archPbMoO4 crystal was characterized by means of cryogenics bolometric measurements and demonstrates excellent performances as a scintillating bolometer. The energy resolution (0.3% at 1462 keV of 40K), the high light yield (5.2 keV/MeV for γs, and 1.2 keV/MeV for α particles) and the highly efficient particle identification achieved with this detector, representing the high quality of the crystal. As a final proof for the feasibility of the archPbMoO4 crystal as a promising detector to search for the neutrinoless double β-decay of 100Mo, the crystal should be produced using the LTG Czochralski technique to prevent the possible contamination during the crystal growth and to increase the production yield.

The Ca_9RE(VO_4)_7 (RE = La, Nd, Gd) and Ca_10M(VO_4)_7 (M = Li, Na, K) single crystals have been grown by the Czochralski method. The binary vanadates are isostructural to “whitlockite” mineral (rhombohedral symmetry, R 3 c space group). Their thermal conductivity has been investigated in the range 50 K–300 K parallel to the c axis. For Ca_9Gd(VO_4)_7 crystals, the thermal conductivity has been investigated in the range 300 K–550 K also. Additionally, for the Ca_10M(VO_4)_7 (M = Li, Na, K) crystals the heat capacity has been studied in the temperature range 80 K–300 K. The character of the temperature dependence of thermal conductivity is close to that of glasses. The possible reasons of the observed features of the thermal conductivity have been analyzed. Raman spectra of Ca_10M(VO_4)_7 (M = Li, Na, K) crystals have been measured and discussed. The spectral lines were broad and similar to polycrystalline or amorphous solids. These crystals are expected to be suitable for application as efficient nonlinear optic and laser materials.

Ca9Nd(VO4)(7) single crystal was grown by the Czochralski method in inert atmosphere. The crystal structure and chemical composition were studied. Polarized absorption and luminescence spectra were investigated in details. It was found that the Ca9Nd(VO4)(7) crystals belongs to self-activated laser materials with a weak concentration quenching of luminescence. Judd-Ofelt analysis was performed. The emission cross-sections spectra for (4)F3/2 -> (4)I9/2, (4)I11/2, (4)I13/2 transitions were determined. For the first time Raman spectra of the Ca9Nd(VO4)(7) single crystal were recorded and interpreted. (C) 2016 Elsevier B.V. All rights reserved.

Pure and Nd-doped Ca10Li(VO4)7 single crystals were grown by the Czochralski method. The structure of Ca10Li(VO4)7 single crystal was refined starting from a model of Ca10K(VO4)7 using the powder diffraction data collected at a laboratory high-resolution diffractometer. The defect structure of the single crystal was studied with the use of both, high-resolution diffraction using a laboratory instrument and X-ray topographic techniques employing synchrotron radiation at the Hasylab laboratory (Hamburg). Polarized absorption and luminescence spectra of Nd-doped Ca10Li(VO4)7 crystal were investigated in details. The laser oscillation was obtained under flash lamp pumping and the slope efficiency of 0.87% was achieved in the free-running mode. Preliminary examination of lasing properties points that Ca10Li(VO4)7:Nd crystal can be a highly efficient solid state laser medium. Crystals of this kind are expected to be suitable for application as efficient non-linear optics materials.

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/cm(2). The optical breakdown thresholds of Ca3Y2(BO3)(4):Nd and Ca3Gd2(BO3)(4):Nd crystals is approximately twice as low.

The Ca9Y(VO4)7-x(PO4)x (X=0-7) solid solution samples of synthesized ceramics and single crystals grown by the Czochralski method were characterized by powder and single crystal X-ray diffraction and optical spectroscopy. The microhardness Hv and fracture toughness K1c of solid solution single crystals were investigated.

We report on the first compelling observation of α decay of 151Eu to the ground state of 147Pm. The measurement was performed using a 6.15 g Li6Eu(BO3)3 crystal operated as a scintillating bolometer. The Q-value and half-life measured are: Q = 1948.9±6.9(stat.) ± 5.1(syst.) keV, and T1/2 = (4.62 ± 0.95(stat.) ± 0.68(syst.)) × 1018 y. The half-life prediction of nuclear theory using the Coulomb and proximity potential model are in good agreement with this experimental result.

The pure Ca3Y2(BO3)4 single crystals were grown by the Czochralski method using an inert and oxygen containing atmospheres and characterized by means of powder X-ray diffraction, optical spectroscopy. The microhardness Hv and fracture toughness K1c of single crystals were studied too. The peculiarities of Ca3Y2(BO3)4 crystal growth are discussed.

N. Casali, S.S. Nagorny, F. Orio, L. Pattavina, J.W. Beeman, F. Bellini, L. Cardani, I. Dafinei, S. Di Domizio, M.L. Di Vacri, L. Gironi, M.B. Kosmyna, B.P. Nazarenko, S. Nisi, G. Pessina, G. Piperno, S. Pirro, C. Rusconi, A.N. Shekhovtsov, C. Tomei, and M. Vignati INFN Laboratori Nazionali del Gran Sasso, I-67010 Assergi (AQ) Italy Dipartimento di Scienze Fisiche e Chimiche, Università degli Studi dell’Aquila, I-67100 Coppito (AQ) Italy INFN Sezione di Roma, I-00185 Roma Italy Dipartimento di Fisica Università di Roma La Sapienza, I-00185 Roma Italy Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA Dipartimento di Fisica, Università di Genova and INFN Sezione di Genova, I-16146 Genova Italy Dipartimento di Fisica, Università di Milano-Bicocca, Milano I-20126 Italy INFN Sezione di Milano Bicocca, Milano I-20126 Italy Institute for Single Crystals, National Academy of Sciences of Ukraine, 61001 Kharkov, Ukraine and Institute for Nuclear Research, National Academy of Sciences of Ukraine, 03680 Kyiv, Ukraine (Dated: June 11, 2021)

The present paper briefly overviews the application of the Czochralski method for growth of a set of oxide crystals for photonics, as well as the design of equipment at the Institute for Single Crystals, NAS of Ukraine. The examples of crystal growth and their characterization are described. The simultaneous Q-switched lasing and self-Raman frequency conversion were demonstrated in Nd-doped PbWO4 and PbMoO4 crystals grown by the Czochralski method. The slope lasing efficiency obtained for a PbMoO4:Nd3+ laser is the best result for all the crystals with the scheelite-type structure. A detection unit with high scintillation characteristics based on a large volume (V approximate to 350 cm(3)) CdWO4 crystal was produced. Crystal growth procedures and properties of new double tungstate and vanadate crystals are presented, too.

Equivalent curcuits were used to study peculiarities of polarization processes in PbMoO4:Nd(3+ )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.

Pure and Nd-doped disordered calcium vanadate Ca10K(VO4)7, Ca10Li(VO4)7, Ca9La(VO4)7 and Ca9Y(VO4)7 single crystals with high optical quality were grown by Czochralsky technique in inert atmosphere. Their polarized absorption spectra were investigated in details. Spectroscopic parameters for Nd3+ ion were determined with Judd–Ofelt theory (J–O) and theory of f–f transition intensities for systems with intermediate or anomalously strong configuration interaction (ICI or ASCI approximation). Spectral and temporal characteristics of luminescence associated with 4F3/2→4I9/2, 4I11/2 and 4I13/2 transitions were analyzed, luminescence branching ratios and radiative lifetimes were calculated. Thermal expansion coefficients were determined for Ca9La(VO4)7 and Ca9Y(VO4)7 crystals in the directions of a and c crystallographic axes. Principal thermo-optic coefficients dno/dT and dne/dT were measured for Ca9La(VO4)7 crystal in the spectral range of 0.4–1.1μm. The potential of disordered vanadates for laser applications was analyzed from the point of thermal effects.

Pure and Yb-doped Ca9Y(VO4)7 (CYVO) single crystals were grown using the Czochralski method. Their crystal structure was determined using powder diffraction and the defect structure was characterized using high-resolution diffraction. The undoped crystal is found to be composed of a transparent and an opaque parts. In the latter, yttrium-rich inclusions were detected. Spectral-kinetic characteristics of Yb3 -doped crystals is reported.

Ca9 Ln(VO4)7 single crystals (Ln = Y, La, or Gd) have been grown by the Czochralski method. The grown crystals deviate from the stoichiometric ratio Ca/Ln; this deviation increases in the series from Y to Gd.

Ca10Yb0.3 K-0.1(VO4)(7) single crystals have been grown for the first time. Absorption and luminescence spectra, luminescence decay kinetics of F-2(5/2) level for Yb(3+ )ion are investigated.

PbMoO4:Nd3+ single crystals have been grown using different doping schemes. Their dielectric properties have been studied in the temperature range of 20–550°C at frequencies from 25 to 106 Hz. The activation energies of dielectric relaxation are determined for all samples, and the Nd3+ luminescence decay kinetics is studied. The most realistic models of activator centers in PbMoO4:Nd3+ crystals are proposed based on the optical and dielectric spectroscopy data.