Vladimir V. Kochurikhin

Growth of Ca8La2(PO4)6O2 single crystals as substrates for GaN epitaxial growth

Abstract 〈0xa00xa00xa01〉 oriented Ca 8 La 2 (PO 4 ) 6 O 2 (CLPA) single crystals with the apatite structure are grown by the Czochralski method. Compositional and lattice parameter uniformity of CLPA is discussed in relation to the growth conditions. Since their lattice constant have excellent matching with three times that of GaN, they are candidates as new substrates for the growth of high-quality GaN epitaxial layers.

Growth and piezoelectric properties of Ca3Nb(Ga1?xAlx)3Si2O14 (x = 0.25 and 0.50) single crystals

One inch Ca3NbGa3Si2O14 (CNGS) and Ca3Nb(Ga1?xAlx)3Si2O14 (CNGAS) bulk crystals with an ordered langasite-type structure were grown by a Czochralski method. CNGS bulk single crystals without cracks could be grown, while CNGAS bulk crystals with x = 0.25 and 0.50 included some cracks even under improved growth conditions. Lattice parameters and anisotropy on the structure of grown crystals were systematically decreased and increased by increasing the Al concentration, respectively. Although the density and dielectric constant ?11 of an X-cut sample of the CNGAS crystal with x = 0.25 were decreased by Al substitution, the electromechanical coupling factor k12 and piezoelectric constant d11 were increased. The effects of Al substitution on piezoelectric properties were almost consistent with previous reports on the disordered langasite-type crystals except for their amount of change.

Investigation of a Tb-Doped HfO2 Single Crystal Grown by a Skull Melting Method

HfO2 Has High Effective Atomic Number and No Radioactive-Isotope as the Background Source, and it Can Be the Candidate for the High-Stopping Scintillator Instead of Lu2SiO5:Ce Scintillator Used in Medical Imaging, Astronomy and etc. However, HfO2 Has an Extremely High Melting Point of 2774 °C, and it Is Difficult to Grow the Crystal from the Melt Using Crucible, as there Is No Suitable Metals, which Can Survive around that Temperature. Thus, Czochralski, Bridgman, and Micro-Pulling down Method Cannot Be Applied. Therefore we Investigated Optical Properties of a 17-mol% b-Doped (Stabilized) HfO2 Crystal Grown by the Skull Melting Method, and this Crystal Had a High Refractive Index of 2.5 at 550 nm, and the Maximum Emission Peak at ~550 nm from 5D4 Excited States of Tb3+. In Addition, we Found the Radiation Reaction of the Crystal Irradiated with Alpha and Gamma Rays Measuring with a Photomultiplier.

Crystal growth of GdVO4 by the micropulling down method

Undoped and neodymium-doped (1 at %) gadolinium vanadate (GdVO4) single crystals 5 mm in diameter and up to 25 mm in length, uniform in cross section, have been grown by the micropulling down method. The chemical and phase compositions of the crystals have been determined, and their absorption spectra were measured.

Growth and scintillation properties of Eu and Ce doped LiSrI 3 single crystals

In this study, Eu and Ce doped LiSrI3 single crystals were explored and the scintillation performance was reported at the first time. Eu and Ce doped LiSrI3 single crystals were grown by the Bridgman–Stockbarger method in a quartz ampoule with 3xa0mm inner diameter. Growth rate was 0.06xa0mm/min. Circular samples with 1xa0mm thickness were obtained from the grown crystal. The grown Eu doped LiSrI3 crystal demonstrated Eu2+ 4f–5d emission peak at 420xa0nm under alpha-ray excitation. In the case of Ce doped one, double emission peaks at 360 and 400xa0nm were observed. The light yield of the Eu doped LiSrI3 was around 35,000 photon/MeV for 662xa0keV gamma-ray and 24,000 photon/5.5xa0MeV for alpha-ray. Energy resolution of the Eu doped LiSrI3 was 5.2%@662xa0keV. Scintillation decay time of the grown Ce and Eu doped LiSrI3 under 662xa0keV gamma-ray was 23.8xa0ns (50%) 212xa0ns (50%) and 545xa0ns 100%, respectively.

Optical and scintillation properties of lutetium vanadate single crystal

We studied optical- and scintillation properties of LuVO<inf>4</inf> single crystal grown by the Czochralski (CZ) method with RF heating system. The vanadate crystal show high transmittance (∼ 80 %) in the 400–900 nm wavelength range. In both of photo- and radio-luminescence spectra, intense peak around 400–500 nm which was ascribed to the transition from triplet state of VO<inf>4</inf>³⁻ was clearly observed. The main decay time component was about 17 μs under 340 nm excitation. The scintillation light yield of LuVO<inf>4</inf> single crystals were evaluated to be about 10300 ph/MeV from the ¹³⁷Cs excited pulse height spectra, respectively.