An experimental study of energy dependence of saturation thickness of multiply scattered gamma rays in zinc

The present measurements have been carried out to study the energy dependence of saturation thickness of multiply scattered gamma photons from zinc targets of various thicknesses. An inverse response matrix approach has been implemented to convert the observed pulse-height distribution of a NaI (Tl) scintillation detector to a photon spectrum and hence to improve the statistical error. These results in extractions of intensity distribution of multiply scattered events originating from interactions of 662 keV photon with thick target of zinc material. The observed pulse-height distributions are a composite of singly and multiply scattered events. To evaluate the contribution of multiply scattered events only, the spectrum of singly scattered events contributing to inelastic Compton peak has been reconstructed analytically. The scattered photons have been detected by a properly shielded NaI (Tl) gamma ray detector placed at different angle to the incident beam. The saturation thickness at which the number of multiply scattered events saturates has been measured. The signal-to-noise ratio and multiple scatter fractions have been found to be decreasing with increasing target thickness. The self-absorption correction factor improves the multiply scattered photon intensity but not the saturation thickness. The same experiment has been repeated with HPGe detector at 90° scattering angle. The results obtained with NaI (Tl) and HPGe detector show the same trend. The experimental results have been found to support the Monte Carlo calculations

An experimental study of energy dependence of saturation thickness of multiply scattered gamma rays in zinc

339-344The present measurements have been carried out to study the energy dependence of saturation thickness of multiply scattered gamma photons from zinc targets of various thicknesses. An inverse response matrix approach has been implemented to convert the observed pulse-height distribution of a NaI (Tl) scintillation detector to a photon spectrum and hence to improve the statistical error. These results in extractions of intensity distribution of multiply scattered events originating from interactions of 662 keV photon with thick target of zinc material. The observed pulse-height distributions are a composite of singly and multiply scattered events. To evaluate the contribution of multiply scattered events only, the spectrum of singly scattered events contributing to inelastic Compton peak has been reconstructed analytically. The scattered photons have been detected by a properly shielded NaI (Tl) gamma ray detector placed at different angle to the incident beam. The saturation thickness at which the number of multiply scattered events saturates has been measured. The signal-to-noise ratio and multiple scatter fractions have been found to be decreasing with increasing target thickness. The self-absorption correction factor improves the multiply scattered photon intensity but not the saturation thickness. The same experiment has been repeated with HPGe detector at 90° scattering angle. The results obtained with NaI (Tl) and HPGe detector show the same trend. The experimental results have been found to support the Monte Carlo calculations

Experimental investigation of saturation depth of 0.662 MeV gamma rays in copper

111-115The effect of target thickness on 0.662 MeV multiply Compton scattered gamma photon has been studied experimentally. An intense collimated beam, obtained from 6-Ci¹³⁷Cs source, is allowed to impinge on a rectangular copper target of varying thickness and the scattered photons are detected by a properly shielded NaI(Tl) scintillation detector, having dimensions 51φ mm51 mm, placed at 90º to the incident beam. The subtraction of events under the analytically reconstructed full energy peak from the events recorded under the observed inelastic peak results in multiply scattered events having energy same as in single scattering. The target thickness at which the number of multiply scattered events saturates has also been determined. The signal-to-noise ratio is found to be decreasing with increasing target thickness. Monte Carlo calculation supports the present experimental results

Tuning ferroelectricity by manipulating the global and local structure in a lead-free Sr-doped Ba(Ti

The effect of 5% Sr substitution at the Ba site in Ba(Ti1-x Snx)O3 (BTSnx) system is investigated for x=0.05, 0.075, and 0.12 compositions. The phase transition studies were carried out using dielectric, high-resolution X-ray diffraction, and PE hysteresis loop measurements. Rietveld refinements, along with dielectric studies on strontium-doped BTSnx reveal that the inter-ferroelectric phase boundaries observed in pure BaTiO3 approach the Tc line, with morphotropic phase boundary like behaviour. The PE hysteresis loops show enhanced polarization (≈ 190%) in Sr-doped BTSn5, which is attributed to the inter-ferroelectric phase instability (which facilitates polarization rotation, phase boundary motion, and domain wall motion), enhanced tetragonality (c/a), and increased unit-cell polarization evident from the amplitude of frozen phonon mode GM4− corresponding to the zone center of the cubic Brillouin zone. The ferroelectric polarization observed in the average-cubic-structure state of Sr-doped BTSn12 is attributed to the cooperative polar off-centre displacements of A (Ba2+/Sr2+) and B (Ti4+/Sn4+) site cations along 〈100〉 and 〈111〉 directions, respectively. Further, Sr-doped BTSn12 has high dielectric constant and low loss which makes this material an important composition for various technological applications

Role of oxygen vacancies on relaxation and conduction behavior of KNbO<SUB>3</SUB> ceramic

The temperature and frequency dependent dielectric and conductivity properties were measured on as-sintered as well as oxygen annealed KNbO<SUB>3</SUB> ceramics. The results show that in addition to phase transition peaks, well defined relaxation peaks are observed in the temperature range 450-700 K. These peaks could be suppressed by annealing the samples in the oxygen atmosphere. The dc conductivity and maximum dielectric constant values decreases after oxygen annealing. Activation energy, calculated from dielectric relaxation and conductivity data on the samples, suggests that both the processes are due to doubly charged oxygen vacancies formed during sintering process. Dielectric relaxation is attributed to the hopping of oxygen vacancies in the six equivalent sites in perovskite structure. The dielectric and conductivity behaviors are influenced by the density of the samples. The results are explained on the basis of defect concentration and their dynamics

Oxygen-vacancy-related dielectric relaxation and electric conduction in KNbO<SUB>3</SUB> ceramic

The temperature and frequency dependent dielectric and conductivity properties were measured on as-sintered as well as oxygen annealed KNbO3 ceramics. The results show that in addition to phase transition peaks, well defined relaxation peaks are observed in the temperature range 450-700 K. These peaks could be suppressed by annealing the samples in the oxygen atmosphere. The dc-conductivity and maximum dielectric constant values decreases after oxygen annealing. The results are explained on the basis of defect concentration and their dynamics

Role of

We report here the role of component freezing of three-dimensional polar ($\Gamma_{4}^{-}$ ) phonon mode corresponding to the center of cubic Brillouin zone in tuning the structure-property correlations of a scientifically enriched and technologically important barium-titanate–based eco-friendly functional material (Ba0.92Ca0.08)(Zr0.05Ti0.95−xSnx)O3; BCZTSnx $(0\leq x\leq 0.10)$ synthesized via solid-state reaction method. The combined X-ray diffraction, Raman spectroscopic analysis, and temperature-dependent dielectric studies have revealed the presence of several crystallographic phase transitions with coexisting phases, viz., $P4mm \rightarrow (P4mm+Amm2+R3m) \rightarrow (Amm2+R3m) \rightarrow R3m \rightarrow (Pm\overline{3}m+R3m)$ , as a function of Sn(x) content. These crystallographic phases, viz., P4mm, Amm2, and R3m results due to freezing of the component(s) of $\Gamma_{4}^{-}$ phonon mode (belonging to $Pm\overline{3}m$ space group), with the respective order parameter directions (0,0,a), (a,a,0), and (a,a,a) leading to ferroelectric polarization along $\langle{}001\rangle$ , $\langle{}110\rangle$ and $\langle{}111\rangle$ directions, respectively. The ceramic composition corresponding to $x = 0.025$ exhibits a significant reduction in the coercive field (Ec) and an enhancement in ferroelectric polarization (Pr) in comparison to $x = 0$ , inferred from PE loop measurements. The enhancement in ferroelectric polarization at $x = 0.025$ has been attributed to the inter-ferroelectric three-phase $(P4mm+Amm2+R3m)$ coexistence around this composition and significantly enhanced amplitudes of ferroelectric phonon modes corresponding to orthorhombic and rhombohedral phases, calculated using the symmetry mode analysis technique. The existence of a high ferroelectric polarization and low coercive field may lead to $x = 0.025$ composition as an eco-friendly candidate for ferroelectric memory devices

Temperature dependence photo-luminescence of Nd<SUP>3+</SUP> doped PLZT ceramic

Temperature dependence of photo-luminescence for Nd<SUP>3+</SUP> doped PLZT(9/65/35) was measured across its structural phase transition temperature. The absorption corresponding to <SUP>4</SUP> I<SUB>9/2</SUB>→ <SUP>4</SUP> F<SUB>5/2</SUB>, <SUP>2</SUP> H<SUB>9/2</SUB> energy level near 808 nm was used for exciting the sample. The major emission bands at 0.9, 1.06, and 1.34 μ m were observed. No shift in the peak position of these emission bands was observed across the diffused structural transition with increase in temperature. However, a 10% increase in FWHM was observed. The absence of any discernible peak shift is attributed to the shielding of the intra-configurational 4f-4f transitions, in trivalent Nd<SUP>3+</SUP> ions, by external 5 s and 5d orbitals. The red shifted phonon side bands appeared with increase in temperature

Effect of oxidant-to-fuel ratios on phase formation of PLZT powder: prepared by gel-combustion

Single phase, PLZT powder was synthesized using gel-combustion route. It has been observed that fuel-to-oxidant ratio affects the initial phase formation. Higher fuel content leads to direct formation of crystalline perovskite PLZT powder due to substantial rise in the temperature during the redox reaction. Perovskite PLZT phase formation takes place at 550 °C, without any intermediate phase formation, for stoichiometric fuel-to-oxidant ratio. The crystallite size was found to be independent of fuel-to-oxidant ratio when the ash is heated above 700 °C