A quadrupole coupling induced 47Ti and 49Ti satellite background which transforms into well-defined lines below T(c) in the ferroelectric phase has been observed cubic of an ultrapure BaTiO3 single crystal. The results demonstrate coexistence a displacive order-disorder component transition mechanism tetragonal breaking symmetry due to biased Ti motion between off-center sites paraelectric above T(c).

Abstract An overview of recognized structural defects, impurities and related trapping levels their role in the scintillation mechanism is provided discussed single crystal materials belonging to tungstate, Ce‐ or Pr‐doped aluminum perovskite, garnet finally Ce‐doped silicate scintillators. New achievements open problems deeper understanding electron hole self‐trapping phenomena nature defects structure ability localize migrating charge carriers are indicated. Fast optical ceramics...

Thermally stimulated luminescence (TSL) glow curves and emission spectra were studied in undoped Ce-doped ${\mathrm{Lu}}_{3}{\mathrm{Al}}_{5}{\mathrm{O}}_{12}$ single crystals by wavelength resolved TSL measurements the $10--310\phantom{\rule{0.3em}{0ex}}\mathrm{K}$ temperature range. Isothermal phosphorescence $10--100\phantom{\rule{0.3em}{0ex}}\mathrm{K}$ range also performed, which point to existence of a tunneling-driven radiative recombination process. These processes can explain...

Resonant piezoelectric spectroscopy shows polar resonances in paraelectric ${\mathrm{SrTiO}}_{3}$ at temperatures below 80 K. These become strong $T<40\text{ }\text{ }\mathrm{K}$. The are induced by weak electric fields and lead to standing mechanical waves the sample. This response does not exist paraelastic nor just ferroelastic phase transition. interpretation of is related twin walls which low close analogy with known behavior ${\mathrm{CaTiO}}_{3}$. different from...

The observation of first order satellites in the NMR spectra $^{47}\mathrm{Ti}$ and $^{49}\mathrm{Ti}$ cubic phases $\mathrm{Ba}\mathrm{Ti}{\mathrm{O}}_{3}$ $\mathrm{Sr}\mathrm{Ti}{\mathrm{O}}_{3}$ as well $^{18}\mathrm{O}$ enriched $\mathrm{Sr}\mathrm{Ti}^{18}\mathrm{O}_{3}$ demonstrates presence nonzero quadrupole coupling at Ti sites all these systems. This is incompatible with central position oxygen octahedron requires off-center dynamic disorder even paraelectric phase. potential...

An isotropic 207Pb NMR spectrum corresponding to the glassy matrix with spherical shell type Pb shifts from cubic sites, as well an anisotropic spectral component polar nanoclusters a shift parallel [111] direction, have been observed in PbMg(1/3)Nb(2/3)O3 (PMN) single crystal. This represents microscopic confirmation of model relaxors first proposed by Burns and Dacol. A sudden increase intensity cluster line is seen for electric fields larger than critical field around 210 K. demonstrates...

Ti and Sr nuclear magnetic resonance spectra of 18O enriched SrTiO3 (STO-18) provide direct evidence for disorder already in the cubic phase show that ferroelectric transition at T(C)=24 K occurs two steps. Below 70 rhombohedral polar clusters are formed tetragonal matrix. These subsequently grow concentration, freeze out, percolate, leading to an inhomogeneous state below T(C). This shows elusive STO-18 is indeed connected with local symmetry lowering implies existence order-disorder...

The work reports the results on 71Ga and 27Al NMR investigation of gallium aluminum ions distribution over tetrahedral octahedral positions in Y3Al5–x GaxO12:Ce single crystals Lu3Al5–xGaxO12:Ce single-crystalline epitaxial films. content x varies between 0 5 0.3 2 films.. We find that both Y- Lu-based solid solutions larger are preferably located at position while smaller prefer garnet host. Based data, dependence fractional occupation parameters site Ga Al is determined. In particular,...

On the basis of extensive experimental studies Pb${}_{1\ensuremath{-}x}$Ba${}_{x}$(Fe${}_{1/2}$Nb${}_{1/2}$)O${}_{3}$ (PFN-BFN) and Pb(Fe${}_{1/2}$Nb${}_{1/2}$)${}_{1\ensuremath{-}x}$Ti${}_{x}$O${}_{3}$ (PFN-PT) single crystals by several methods, we have proposed phase diagrams describing magnetic properties these solid solutions. The comprehensive consideration PFN-based solutions has shown that can be explained on a model suggested earlier for pure PFN [Phys. Rev. Lett. 105, 257202...

Investigations of impurity centers, electrical resistivity and microstructure BaTiO3 ceramics doped with rare-earth ions Y, La, Nd, Sm, Dy Lu at concentrations x = 0.001–0.005 were carried out. Electron paramagnetic resonance, X-ray diffraction electron microscopy used for measurements. The most intense EPR lines shown to belong complexes Fe3+–VO Ti3+–Ln3+ (Ln ion, VO oxygen vacancy). A change in symmetry the center transition temperature from ferroelectric paraelectric phase has been...

The autolocalization of free electrons at regular lattice sites, namely complex anions, has been demonstrated by ESR measurements. It shown that the centre is a shallow donor; its energy level situated meV below bottom conduction band. At temperatures 50-60 K captured are detrapped and formation other paramagnetic centres occurs. In La-doped , an enhanced cross-section for electron trapping impurity with respect to undoped samples found. contrast case tungstates, no intrinsic oxygen hole...

We report intense terahertz emission from lead zirconate titanate (PZT) tubular nanostructures, which have a wall thickness around 40 nm and protrude on n-type Si substrates. Such is totally absent in flat PZT films or bulk; hence the effect attributed to nanoscale geometry of tubes. The radiation emitted within 0.2 ps, spectrum exhibits broad peak 2 8 THz. This gap frequency conventional semiconductor devices, such as ZnTe, an order magnitude higher than that well-studied p-InAs, due...

Participation of shallow and deep traps in the processes energy transfer capture is studied by means timeresolved emission spectroscopy thermoluminescence several groups Ce 3+ Pr -doped complex oxide single crystal scintillators.Tunnelling-driven recombination are distinguished all examined materials: closely spaced electron hole give rise to 1 phosphorescence decays at low temperatures Ce-doped aluminum garnets perovskites, while thermally assisted tunneling process proposed explain...

The processes of hole and electron localization in ${\text{YAlO}}_{3}$ single crystals were investigated by electron-spin resonance. It was found that holes created UV or x-ray irradiation are trapped at regular oxygen ions forming two types ${\text{O}}^{\ensuremath{-}}$ centers corresponding to inequivalent which located Y Al planes, respectively. can be either autolocalized additionally stabilized a defect the neighborhood ion such as yttrium vacancy an impurity site. This leads variety...

We have fabricated new perovskite multiferroic PbFeSbO3 with a high degree (up to 0.9) of chemical ordering and unexpectedly high-temperature magnetic relaxor properties, which can barely be described within concepts conventional spin glass physics. Notably, we found that the field-temperature phase diagram this material, in extremely wide temperature interval, contains de Almeida–Thouless-type critical line, has been subject long debates regarding its possible experimental realization....

Eu-doped ternary sulfides of general formula ALnS2 (A = Na, K, Rb; Ln La, Gd, Lu, Y) are presented as a novel interesting material family which may find usage X-ray phosphors or solid state white light emitting diode (LED) lighting. Samples were synthesized in the form transparent crystalline hexagonal platelets by chemical reaction under flow hydrogen sulfide. Their physical properties investigated means diffraction, time-resolved photoluminescence spectroscopy, electron paramagnetic...

Single crystals of the undoped Cs2HfCl6 were grown using vertical Bridgman method. Photoluminescence spectra and decays measured in extended temperature range 8–500 K approximated by a phenomenological model. Self-trapped exciton defect-related emissions clearly distinguished with onset thermal quenching above room temperature. Electron paramagnetic resonance experiment revealed formation two configurations Vk center (Cl2– molecular ion) at low temperatures. One centers is created hole...

The role and effect of stable Ce <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4+</sup> centers in Ce-doped LuAG single crystal scintillator is further studied by means measurements several optical, luminescence scintillation characteristics. Two LuAG:Ce samples are compared: one them the dominating xmlns:xlink="http://www.w3.org/1999/xlink">4 +</sup> center stabilized high concentration Mg xmlns:xlink="http://www.w3.org/1999/xlink">2+</sup>...

The ${F}^{+}$ center consisting of an electron trapped at oxygen vacancy (${V}_{\mathrm{O}}$) was investigated in deficient ${\mathrm{Y}}_{3}{\mathrm{Al}}_{5}{\mathrm{O}}_{12}$ (YAG) garnet crystals by paramagnetic resonance (EPR) techniques. measurements were performed the wide temperature interval 5--450 K and frequency range 9.4--350 GHz using both conventional continuous-wave pulse EPR experiments. Pulse electron-nuclear double applied to resolve hyperfine interaction with surrounding...

Electron traps based on regular Pb sites perturbed by oxygen vacancies ${(V}_{\mathrm{O}})$ in high purity undoped ${\mathrm{PbWO}}_{4}$ have been revealed and studied electron spin resonance (ESR) thermally stimulated luminescence (TSL) measurements. Detailed analysis of ESR spectra parameters $(g$ factor, hyperfine, superhyperfine structures) along with the variation concentration after annealing inert atmospheres had shown that centers are ${\mathrm{Pb}}^{+}\ensuremath{-}{V}_{\mathrm{O}}$...