Results on fracture mechanics and crack propagation have been obtained, making use of Vickers microhardness studies on two different crystallographic planes [(110) and (001)] of flux grown erbium aluminate crystals in...Results on fracture mechanics and crack propagation have been obtained, making use of Vickers microhardness studies on two different crystallographic planes [(110) and (001)] of flux grown erbium aluminate crystals in the load ranging from 10-100 g. The variation of microhardness with load which is best explained by Hays and Kendall's law leads to the load independent values of hardness. Classification of cracks is dealt with and it is reported that the transition from Palmqvist to median types of cracks occurs at higher loads. The values of fracture toughness (K_C), and brittleness index (B_i) are calculated using median types of cracks.展开更多
Nanoparticles of neodymium orthophosphate （NdPO4） were prepared through a facile wet co-precipitation technique. The X-ray diffraction （XRD） studies revealed the material belonging to monoclinic monazite phase wit...Nanoparticles of neodymium orthophosphate （NdPO4） were prepared through a facile wet co-precipitation technique. The X-ray diffraction （XRD） studies revealed the material belonging to monoclinic monazite phase with crystallite size of 30.8 nm. Scanning electron microscopic studies showed that the material was composed of a large number of agglomerated spherical particles having grain size of 92 nm. Thermogravimetric analysis suggested that the structural phase transition was seen above 800 °C. The spectroscopic investigations were carried out using Fourier transform infrared spectroscopy （FTIR）. UV-VIS-NIR ab-sorption spectrophotometer showed various transitions from the ground state 4I9/2 to various excited states within the 4f shell and the optical band gap came out to be 3.3 eV. The dielectric constant （ε′）, dielectric loss （tanδ） and ac conductivity ln（σac） were measured in the frequency range of 5 kHz to 1 MHz and in the temperature range of 40 to 500 °C. The dielectric measurement suggested that there was a shift in the value of transition temperature （Tc）, thereby indicating relaxor behaviour of the material. The activation energy value decreased with increase in frequency, thereby suggesting the role of mixed ionic-polaronic conduc-tivity.展开更多
Neodymium-doped barium phosphate(NdBP)was prepared as single crystal by room temperature solution technique known as gel encapsulation technique.Single crystal X-ray diffraction shows that the crystal belongs to ortho...Neodymium-doped barium phosphate(NdBP)was prepared as single crystal by room temperature solution technique known as gel encapsulation technique.Single crystal X-ray diffraction shows that the crystal belongs to orthorthombic system.The flower type morphology was observed by scanning electron microscope(SEM)and the stoichiometric composition of the prepared crystal was observed by energy dispersive X-ray analysis(EDAX).The presence of functional group and other groups was studied by Fourier transform infrared spectroscopy(FTIR).The electrical properties of these materials like dielectric constant(ε′),dieletric loss(tan σ)and ac conductivity[ln(σac)]was studied at different temperatures ranging from 40℃ to 420℃ in the frequency range of 5 kHz to 1 MHz.The activation energy values decreases with increase in frequency suggesting that the conduction mechanism is because of hopping of charge carriers.展开更多
文摘Results on fracture mechanics and crack propagation have been obtained, making use of Vickers microhardness studies on two different crystallographic planes [(110) and (001)] of flux grown erbium aluminate crystals in the load ranging from 10-100 g. The variation of microhardness with load which is best explained by Hays and Kendall's law leads to the load independent values of hardness. Classification of cracks is dealt with and it is reported that the transition from Palmqvist to median types of cracks occurs at higher loads. The values of fracture toughness (K_C), and brittleness index (B_i) are calculated using median types of cracks.
文摘Nanoparticles of neodymium orthophosphate （NdPO4） were prepared through a facile wet co-precipitation technique. The X-ray diffraction （XRD） studies revealed the material belonging to monoclinic monazite phase with crystallite size of 30.8 nm. Scanning electron microscopic studies showed that the material was composed of a large number of agglomerated spherical particles having grain size of 92 nm. Thermogravimetric analysis suggested that the structural phase transition was seen above 800 °C. The spectroscopic investigations were carried out using Fourier transform infrared spectroscopy （FTIR）. UV-VIS-NIR ab-sorption spectrophotometer showed various transitions from the ground state 4I9/2 to various excited states within the 4f shell and the optical band gap came out to be 3.3 eV. The dielectric constant （ε′）, dielectric loss （tanδ） and ac conductivity ln（σac） were measured in the frequency range of 5 kHz to 1 MHz and in the temperature range of 40 to 500 °C. The dielectric measurement suggested that there was a shift in the value of transition temperature （Tc）, thereby indicating relaxor behaviour of the material. The activation energy value decreased with increase in frequency, thereby suggesting the role of mixed ionic-polaronic conduc-tivity.
文摘Neodymium-doped barium phosphate(NdBP)was prepared as single crystal by room temperature solution technique known as gel encapsulation technique.Single crystal X-ray diffraction shows that the crystal belongs to orthorthombic system.The flower type morphology was observed by scanning electron microscope(SEM)and the stoichiometric composition of the prepared crystal was observed by energy dispersive X-ray analysis(EDAX).The presence of functional group and other groups was studied by Fourier transform infrared spectroscopy(FTIR).The electrical properties of these materials like dielectric constant(ε′),dieletric loss(tan σ)and ac conductivity[ln(σac)]was studied at different temperatures ranging from 40℃ to 420℃ in the frequency range of 5 kHz to 1 MHz.The activation energy values decreases with increase in frequency suggesting that the conduction mechanism is because of hopping of charge carriers.
