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Papers by Ramaraghavulu Rama

Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy, 2015

h i g h l i g h t s Luminescence properties of individually doped Tb 3+ , Sm 3+ and codoped (Tb 3... more h i g h l i g h t s Luminescence properties of individually doped Tb 3+ , Sm 3+ and codoped (Tb 3+ + Sm 3+): LZP glasses were separately studied. Existence of energy transfer from Tb 3+ to Sm 3+ was evidenced from emission spectra and explained from energy level diagram. The decrease in emission lifetime of Tb 3+ reveals resonant non-radiative energy transfer from Tb 3+ to Sm 3+. Energy transfer efficiency (g) is calculated to be 88%.

Metals and Materials International, 2016

The heating characteristics of magnetite ore under microwave irradiation were investigated as a f... more The heating characteristics of magnetite ore under microwave irradiation were investigated as a function of incident microwave power, particle size, and magnetite ore mass. The results showed that the heating rate of magnetite ore is highly dependent on microwave power and magnetite ore mass. The maximum heating rate was obtained at a microwave irradiation power of 1.70 kW with a mass of 25 g and particle size between 53-75 µm. The volumetric heating rate of magnetite ore was investigated by measuring the temperature at different depths during microwave irradiation. Microwave irradiation resulted in modification of the microstructure of the magnetite ore, but new phases such as FeO or Fe2O3 were not formed. In addition, the crystal size decreased from 115 nm to 63 nm after microwave irradiation up to 1573 K.

Ferroelectrics, 2014

ABSTRACT Ferroelectric BaBi2Nb2O9 ceramic powders have been prepared using solid state reaction m... more ABSTRACT Ferroelectric BaBi2Nb2O9 ceramic powders have been prepared using solid state reaction method. Samples have been sintered at four different temperatures of 800°C, 900°C, 1000°C and 1100°C each for 5 hrs. The XRD profiles have shown that the sample sintered at 1000°C (optimized) has displayed well defined features. Based on the profiles of XRD and Reitveild refinement analysis, samples are found in orthorhombic space group A21am (36). The thermal properties of the as synthesized sample have been investigated from the profiles of TG-DTA. Morphological analysis has been carried out from the SEM images and elemental analysis from the EDS profiles. For the temperature optimized sample, both Raman and FTIR spectral profiles have been studied. It is interesting to report that we could notice ferroelectric to paraelectric phase transition from the analysis of the dielectric properties as function of temperature (30–350°C) in the frequency range (1k Hz–1M Hz). Ferroelectric nature of the sample has been confirmed from the measurement of its hysteresis loop at the room temperature.

Ferroelectrics, 2012

ABSTRACT LiV3O8 ceramic powders have been prepared using a solid state reaction method at differe... more ABSTRACT LiV3O8 ceramic powders have been prepared using a solid state reaction method at different (500°C, 550°C, 600°C and 700°C) temperatures. The X-ray diffraction profiles of these samples show that the ceramic powder sintered at 600°C has a well defined monoclinic structure in a space group of P21/m (11) with lattice parameters, a = 6.68 Å, b = 3.60 Å, c = 12.03 Å and α = γ = 90o and β = 107° and it is found to be in good agreement with the JCPDS Card No. 72–1193. The SEM image of this ceramic powder shows the distribution of grains in cylindrical rods form. Thermal (TG) property of as prepared precursor LiV3O8 chemicals has been investigated. Raman and FTIR spectra of the temperature optimized (600°C) ceramic powder have been carried out. Besides this, its dielectric constant (ϵ′) and tangent loss as a function of frequency (100 Hz–1 MHz) and conductivities (σac and σdc) have also been understood in evaluating its potentialities for different applications.

Ceramics International, 2011

Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy, 2015

h i g h l i g h t s Luminescence properties of individually doped Tb 3+ , Sm 3+ and codoped (Tb 3... more h i g h l i g h t s Luminescence properties of individually doped Tb 3+ , Sm 3+ and codoped (Tb 3+ + Sm 3+): LZP glasses were separately studied. Existence of energy transfer from Tb 3+ to Sm 3+ was evidenced from emission spectra and explained from energy level diagram. The decrease in emission lifetime of Tb 3+ reveals resonant non-radiative energy transfer from Tb 3+ to Sm 3+. Energy transfer efficiency (g) is calculated to be 88%.

Ceramics International, 2011

Luminescence properties of individually doped Tb 3+ , Sm 3+ and co-doped (Tb 3+ + Sm 3+): LZP gla... more Luminescence properties of individually doped Tb 3+ , Sm 3+ and co-doped (Tb 3+ + Sm 3+): LZP glasses were separately studied. Existence of energy transfer from Tb 3+ to Sm 3+ was evidenced from emission spectra and explained from energy level diagram. The decrease in emission lifetime of Tb 3+ reveals resonant non-radiative energy transfer from Tb 3+ to Sm 3+. Energy transfer efficiency (g) is calculated to be 88%. g r a p h i c a l a b s t r a c t The energy transfer process from Tb 3+ to Sm 3+ in PZL glasses is explained from spectral overlap of Sm 3+ absorption and Tb 3+ emission, luminescence spectra, decay profiles, energy level diagram and energy transfer parameters (g and P). a b s t r a c t The present paper reports on the results pertaining to photoluminescence properties of Tb 3+ , Sm 3+ and energy transfer from Tb 3+ to Sm 3+ ions in lithium zinc phosphate (LZP) glass matrix prepared by melt quenching method. Besides photoluminescence studies thermal stability for the LZP glass is also evaluated from TG-DTA measurement. Tb 3+ doped glasses have exhibited a prominent green emission at 547 nm assigned to 5 D 4 ? 7 F 5 transitions on exciting at k exci = 377 nm. The quenching phenomenon in Tb 3+ emission on varying its concentration has been discussed from cross-relaxations. Sm 3+ incorporated glasses have shown strong orange emission at 603 nm assigned to 4 G 5/2 ? 6 H 7/2 transition upon exciting with k exci = 404 nm. The possibility of energy transfer process taking place between these two ions is understood from the significant spectral overlap of Sm 3+ absorption and Tb 3+ emission. Migration of excitation energy from Tb 3+ ions to Sm 3+ ions at k exci = 375 nm is evaluated from the emission spectra of (0.5 mol.% Tb 3+ + (0.5–2.0 mol.%) Sm 3+) co-doped glasses. The emission intensity of Sm 3+ has enhanced while Tb 3+ emission intensity decreased with an increase in Sm 3+ concentration suggesting the occurrence of energy transfer through cross-relaxations from Tb 3+ (5 D 4) to Sm 3+ (4 G 5/2). The mechanism behind energy transfer process has been further explained from energy level diagram, decay profiles and confirmed by calculating energy transfer parameters (energy transfer efficiency (g) and energy transfer probability (P)) of co-doped glasses. The dipole–dipole interaction is found to be more responsible for energy transfer Tb 3+ (5 D 4) to Sm 3+ (4 G 5/2) ions in LZP glass matrix.

Ferroelectric BaBi 2 Nb 2 O 9 ceramic powders have been prepared using solid state reaction metho... more Ferroelectric BaBi 2 Nb 2 O 9 ceramic powders have been prepared using solid state reaction method. Samples have been sintered at four different temperatures of 800 • C, 900 • C, 1000 • C and 1100 • C each for 5 hrs. The XRD profiles have shown that the sample sintered at 1000 • C (optimized) has displayed well defined features. Based on the profiles of XRD and Reitveild refinement analysis, samples are found in orthorhombic space group A21am (36). The thermal properties of the as synthesized sample have been investigated from the profiles of TG-DTA. Morphological analysis has been carried out from the SEM images and elemental analysis from the EDS profiles. For the temperature optimized sample, both Raman and FTIR spectral profiles have been studied. It is interesting to report that we could notice ferroelectric to paraelectric phase transition from the analysis of the dielectric properties as function of temperature (30–350 • C) in the frequency range (1k Hz–1M Hz). Ferroelectric nature of the sample has been confirmed from the measurement of its hysteresis loop at the room temperature.

LiV 3 O 8 ceramic powders have been prepared using a solid state reaction method at different (50... more LiV 3 O 8 ceramic powders have been prepared using a solid state reaction method at different (500 • C, 550 • C, 600 • C and 700 • C) temperatures. The X-ray diffraction profiles of these samples show that the ceramic powder sintered at 600 • C has a well defined monoclinic structure in a space group of P2 1 /m (11) with lattice parameters, a = 6.68 Å, b = 3.60 Å, c = 12.03 Å and α = γ = 90 o and β = 107 • and it is found to be in good agreement with the JCPDS Card No. 72–1193. The SEM image of this ceramic powder shows the distribution of grains in cylindrical rods form. Thermal (TG) property of as prepared precursor LiV 3 O 8 chemicals has been investigated. Raman and FTIR spectra of the temperature optimized (600 • C) ceramic powder have been carried out. Besides this, its dielectric constant (ε) and tangent loss as a function of frequency (100 Hz–1 MHz) and conductivities (σ ac and σ dc) have also been understood in evaluating its potentialities for different applications.

Lithium titanium phosphate (LiTi 2 (PO 4) 3) ceramic powders have been prepared by a solid state ... more Lithium titanium phosphate (LiTi 2 (PO 4) 3) ceramic powders have been prepared by a solid state reaction method at five different temperatures (800 8C, 900 8C, 1000 8C, 1100 8C and 1200 8C for 5 h each). The XRD profiles have shown that the sample sintered at 1100 8C (optimized) has displayed well-defined features. XRD peaks are in good agreement with the JCPDS Card No. 35-0754 confirming the rhombohedral structure in a space group of R ¯ 3c. The SEM images of the five samples sintered have been examined. EDAX and Raman spectra have been obtained for the LiTi 2 (PO 4) 3 ceramic powder sintered at 1100 8C for analysis. Thermal properties for the as prepared precursor LiTi 2 (PO 4) 3 sample, have been analyzed from the TG-DTA profiles. Besides this, dielectric constant, dielectric loss and conductivities (s ac and s dc) have also been studied for the LiTi 2 (PO 4) 3 ceramic powder.

Li 2 TiO 3 ceramic powders have been developed by a solid state reaction method and those have be... more Li 2 TiO 3 ceramic powders have been developed by a solid state reaction method and those have been sintered at four different temperatures (600 8C, 700 8C, 800 8C and 900 8C) towards the optimization of sintering temperature that has been found to be at 800 8C based on the nature of the XRD profiles. The sample sintered at 800 8C has shown a good crystallinity situation from its XRD peaks and the sample is found to be in monoclinic structure which is in accordance with the reported data of JCPDS 33-0831. The SEM images for samples sintered at 600 8C, 700 8C, 800 and 900 8C, EDAX peaks, FTIR profile have been measured for the temperature optimized (800 8C) sample for understanding the structural details of Li 2 TiO 3 ceramic powders. Besides these, dielectric constant, dielectric loss and a.c. conductivities have been measured for the temperature optimized sample. In order to strengthen the observations made in the XRD profiles at four different temperatures, Raman spectra of those four sintered ceramic powders have also been studied. In respect of the thermal properties, only for the as synthesized (precursor) sample, simultaneous measurement of TG-DTA profiles has been carried out for analysis.

The heating characteristics of magnetite ore under microwave irradiation were investigated as a f... more The heating characteristics of magnetite ore under microwave irradiation were investigated as a function of incident microwave power, particle size, and magnetite ore mass. The results showed that the heating rate of magnetite ore is highly dependent on microwave power and magnetite ore mass. The maximum heating rate was obtained at a microwave irradiation power of 1.70 kW with a mass of 25 g and particle size between 53-75 µm. The volumetric heating rate of magnetite ore was investigated by measuring the temperature at different depths during microwave irradiation. Microwave irradiation resulted in modification of the microstructure of the magnetite ore, but new phases such as FeO or Fe2O3 were not formed. In addition, the crystal size decreased from 115 nm to 63 nm after microwave irradiation up to 1573 K.

A solid-state reaction route-based LiTi 2 À x Eu x (PO 4) 3 was phosphor synthesized for the firs... more A solid-state reaction route-based LiTi 2 À x Eu x (PO 4) 3 was phosphor synthesized for the first time to evaluate its lumi-nescence performance by excitation, emission and lifetime (τ) measurements. The LiTi 2 À x Eu x (PO 4) 3 phosphor was excited at λ exci. = 397 nm to give an intense orange–red (597 nm) emission attributed to the 5 D 0 → 7 F 1 magnetic dipole (ΔJ = ±1) transition and red (616 nm) emission (5 D 0 → 7 F 2), which is an electric dipole (ΔJ = ±2) transition of the Eu 3+ ion. Beside this, excitation and emission spectra of host LiTi 2 (PO 4) 3 powder were also reported. The effect of Eu 3+ concentration on luminescence characteristics was explained from emission and lifetime profiles. Concentration quenching in the LiTi 2 À x Eu x (PO 4) 3 phosphor was studied from the Dexter's model. Dipole–quadrupole interaction is found to be responsible for energy transfer among Eu 3+ ions in the host lattice. The LiTi 2 À x Eu x (PO 4) 3 phosphor displayed a reddish-orange colour realized from a CIE chromaticity diagram. We therefore suggest that this new phosphor could be used as an optical material of technological importance in the field of display devices.

Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy, 2015

h i g h l i g h t s Luminescence properties of individually doped Tb 3+ , Sm 3+ and codoped (Tb 3... more h i g h l i g h t s Luminescence properties of individually doped Tb 3+ , Sm 3+ and codoped (Tb 3+ + Sm 3+): LZP glasses were separately studied. Existence of energy transfer from Tb 3+ to Sm 3+ was evidenced from emission spectra and explained from energy level diagram. The decrease in emission lifetime of Tb 3+ reveals resonant non-radiative energy transfer from Tb 3+ to Sm 3+. Energy transfer efficiency (g) is calculated to be 88%.

Metals and Materials International, 2016

The heating characteristics of magnetite ore under microwave irradiation were investigated as a f... more The heating characteristics of magnetite ore under microwave irradiation were investigated as a function of incident microwave power, particle size, and magnetite ore mass. The results showed that the heating rate of magnetite ore is highly dependent on microwave power and magnetite ore mass. The maximum heating rate was obtained at a microwave irradiation power of 1.70 kW with a mass of 25 g and particle size between 53-75 µm. The volumetric heating rate of magnetite ore was investigated by measuring the temperature at different depths during microwave irradiation. Microwave irradiation resulted in modification of the microstructure of the magnetite ore, but new phases such as FeO or Fe2O3 were not formed. In addition, the crystal size decreased from 115 nm to 63 nm after microwave irradiation up to 1573 K.

Ferroelectrics, 2014

ABSTRACT Ferroelectric BaBi2Nb2O9 ceramic powders have been prepared using solid state reaction m... more ABSTRACT Ferroelectric BaBi2Nb2O9 ceramic powders have been prepared using solid state reaction method. Samples have been sintered at four different temperatures of 800°C, 900°C, 1000°C and 1100°C each for 5 hrs. The XRD profiles have shown that the sample sintered at 1000°C (optimized) has displayed well defined features. Based on the profiles of XRD and Reitveild refinement analysis, samples are found in orthorhombic space group A21am (36). The thermal properties of the as synthesized sample have been investigated from the profiles of TG-DTA. Morphological analysis has been carried out from the SEM images and elemental analysis from the EDS profiles. For the temperature optimized sample, both Raman and FTIR spectral profiles have been studied. It is interesting to report that we could notice ferroelectric to paraelectric phase transition from the analysis of the dielectric properties as function of temperature (30–350°C) in the frequency range (1k Hz–1M Hz). Ferroelectric nature of the sample has been confirmed from the measurement of its hysteresis loop at the room temperature.

Ferroelectrics, 2012

ABSTRACT LiV3O8 ceramic powders have been prepared using a solid state reaction method at differe... more ABSTRACT LiV3O8 ceramic powders have been prepared using a solid state reaction method at different (500°C, 550°C, 600°C and 700°C) temperatures. The X-ray diffraction profiles of these samples show that the ceramic powder sintered at 600°C has a well defined monoclinic structure in a space group of P21/m (11) with lattice parameters, a = 6.68 Å, b = 3.60 Å, c = 12.03 Å and α = γ = 90o and β = 107° and it is found to be in good agreement with the JCPDS Card No. 72–1193. The SEM image of this ceramic powder shows the distribution of grains in cylindrical rods form. Thermal (TG) property of as prepared precursor LiV3O8 chemicals has been investigated. Raman and FTIR spectra of the temperature optimized (600°C) ceramic powder have been carried out. Besides this, its dielectric constant (ϵ′) and tangent loss as a function of frequency (100 Hz–1 MHz) and conductivities (σac and σdc) have also been understood in evaluating its potentialities for different applications.

Ceramics International, 2011

Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy, 2015

h i g h l i g h t s Luminescence properties of individually doped Tb 3+ , Sm 3+ and codoped (Tb 3... more h i g h l i g h t s Luminescence properties of individually doped Tb 3+ , Sm 3+ and codoped (Tb 3+ + Sm 3+): LZP glasses were separately studied. Existence of energy transfer from Tb 3+ to Sm 3+ was evidenced from emission spectra and explained from energy level diagram. The decrease in emission lifetime of Tb 3+ reveals resonant non-radiative energy transfer from Tb 3+ to Sm 3+. Energy transfer efficiency (g) is calculated to be 88%.

Ceramics International, 2011

Luminescence properties of individually doped Tb 3+ , Sm 3+ and co-doped (Tb 3+ + Sm 3+): LZP gla... more Luminescence properties of individually doped Tb 3+ , Sm 3+ and co-doped (Tb 3+ + Sm 3+): LZP glasses were separately studied. Existence of energy transfer from Tb 3+ to Sm 3+ was evidenced from emission spectra and explained from energy level diagram. The decrease in emission lifetime of Tb 3+ reveals resonant non-radiative energy transfer from Tb 3+ to Sm 3+. Energy transfer efficiency (g) is calculated to be 88%. g r a p h i c a l a b s t r a c t The energy transfer process from Tb 3+ to Sm 3+ in PZL glasses is explained from spectral overlap of Sm 3+ absorption and Tb 3+ emission, luminescence spectra, decay profiles, energy level diagram and energy transfer parameters (g and P). a b s t r a c t The present paper reports on the results pertaining to photoluminescence properties of Tb 3+ , Sm 3+ and energy transfer from Tb 3+ to Sm 3+ ions in lithium zinc phosphate (LZP) glass matrix prepared by melt quenching method. Besides photoluminescence studies thermal stability for the LZP glass is also evaluated from TG-DTA measurement. Tb 3+ doped glasses have exhibited a prominent green emission at 547 nm assigned to 5 D 4 ? 7 F 5 transitions on exciting at k exci = 377 nm. The quenching phenomenon in Tb 3+ emission on varying its concentration has been discussed from cross-relaxations. Sm 3+ incorporated glasses have shown strong orange emission at 603 nm assigned to 4 G 5/2 ? 6 H 7/2 transition upon exciting with k exci = 404 nm. The possibility of energy transfer process taking place between these two ions is understood from the significant spectral overlap of Sm 3+ absorption and Tb 3+ emission. Migration of excitation energy from Tb 3+ ions to Sm 3+ ions at k exci = 375 nm is evaluated from the emission spectra of (0.5 mol.% Tb 3+ + (0.5–2.0 mol.%) Sm 3+) co-doped glasses. The emission intensity of Sm 3+ has enhanced while Tb 3+ emission intensity decreased with an increase in Sm 3+ concentration suggesting the occurrence of energy transfer through cross-relaxations from Tb 3+ (5 D 4) to Sm 3+ (4 G 5/2). The mechanism behind energy transfer process has been further explained from energy level diagram, decay profiles and confirmed by calculating energy transfer parameters (energy transfer efficiency (g) and energy transfer probability (P)) of co-doped glasses. The dipole–dipole interaction is found to be more responsible for energy transfer Tb 3+ (5 D 4) to Sm 3+ (4 G 5/2) ions in LZP glass matrix.

Ferroelectric BaBi 2 Nb 2 O 9 ceramic powders have been prepared using solid state reaction metho... more Ferroelectric BaBi 2 Nb 2 O 9 ceramic powders have been prepared using solid state reaction method. Samples have been sintered at four different temperatures of 800 • C, 900 • C, 1000 • C and 1100 • C each for 5 hrs. The XRD profiles have shown that the sample sintered at 1000 • C (optimized) has displayed well defined features. Based on the profiles of XRD and Reitveild refinement analysis, samples are found in orthorhombic space group A21am (36). The thermal properties of the as synthesized sample have been investigated from the profiles of TG-DTA. Morphological analysis has been carried out from the SEM images and elemental analysis from the EDS profiles. For the temperature optimized sample, both Raman and FTIR spectral profiles have been studied. It is interesting to report that we could notice ferroelectric to paraelectric phase transition from the analysis of the dielectric properties as function of temperature (30–350 • C) in the frequency range (1k Hz–1M Hz). Ferroelectric nature of the sample has been confirmed from the measurement of its hysteresis loop at the room temperature.

LiV 3 O 8 ceramic powders have been prepared using a solid state reaction method at different (50... more LiV 3 O 8 ceramic powders have been prepared using a solid state reaction method at different (500 • C, 550 • C, 600 • C and 700 • C) temperatures. The X-ray diffraction profiles of these samples show that the ceramic powder sintered at 600 • C has a well defined monoclinic structure in a space group of P2 1 /m (11) with lattice parameters, a = 6.68 Å, b = 3.60 Å, c = 12.03 Å and α = γ = 90 o and β = 107 • and it is found to be in good agreement with the JCPDS Card No. 72–1193. The SEM image of this ceramic powder shows the distribution of grains in cylindrical rods form. Thermal (TG) property of as prepared precursor LiV 3 O 8 chemicals has been investigated. Raman and FTIR spectra of the temperature optimized (600 • C) ceramic powder have been carried out. Besides this, its dielectric constant (ε) and tangent loss as a function of frequency (100 Hz–1 MHz) and conductivities (σ ac and σ dc) have also been understood in evaluating its potentialities for different applications.

Lithium titanium phosphate (LiTi 2 (PO 4) 3) ceramic powders have been prepared by a solid state ... more Lithium titanium phosphate (LiTi 2 (PO 4) 3) ceramic powders have been prepared by a solid state reaction method at five different temperatures (800 8C, 900 8C, 1000 8C, 1100 8C and 1200 8C for 5 h each). The XRD profiles have shown that the sample sintered at 1100 8C (optimized) has displayed well-defined features. XRD peaks are in good agreement with the JCPDS Card No. 35-0754 confirming the rhombohedral structure in a space group of R ¯ 3c. The SEM images of the five samples sintered have been examined. EDAX and Raman spectra have been obtained for the LiTi 2 (PO 4) 3 ceramic powder sintered at 1100 8C for analysis. Thermal properties for the as prepared precursor LiTi 2 (PO 4) 3 sample, have been analyzed from the TG-DTA profiles. Besides this, dielectric constant, dielectric loss and conductivities (s ac and s dc) have also been studied for the LiTi 2 (PO 4) 3 ceramic powder.

Li 2 TiO 3 ceramic powders have been developed by a solid state reaction method and those have be... more Li 2 TiO 3 ceramic powders have been developed by a solid state reaction method and those have been sintered at four different temperatures (600 8C, 700 8C, 800 8C and 900 8C) towards the optimization of sintering temperature that has been found to be at 800 8C based on the nature of the XRD profiles. The sample sintered at 800 8C has shown a good crystallinity situation from its XRD peaks and the sample is found to be in monoclinic structure which is in accordance with the reported data of JCPDS 33-0831. The SEM images for samples sintered at 600 8C, 700 8C, 800 and 900 8C, EDAX peaks, FTIR profile have been measured for the temperature optimized (800 8C) sample for understanding the structural details of Li 2 TiO 3 ceramic powders. Besides these, dielectric constant, dielectric loss and a.c. conductivities have been measured for the temperature optimized sample. In order to strengthen the observations made in the XRD profiles at four different temperatures, Raman spectra of those four sintered ceramic powders have also been studied. In respect of the thermal properties, only for the as synthesized (precursor) sample, simultaneous measurement of TG-DTA profiles has been carried out for analysis.

The heating characteristics of magnetite ore under microwave irradiation were investigated as a f... more The heating characteristics of magnetite ore under microwave irradiation were investigated as a function of incident microwave power, particle size, and magnetite ore mass. The results showed that the heating rate of magnetite ore is highly dependent on microwave power and magnetite ore mass. The maximum heating rate was obtained at a microwave irradiation power of 1.70 kW with a mass of 25 g and particle size between 53-75 µm. The volumetric heating rate of magnetite ore was investigated by measuring the temperature at different depths during microwave irradiation. Microwave irradiation resulted in modification of the microstructure of the magnetite ore, but new phases such as FeO or Fe2O3 were not formed. In addition, the crystal size decreased from 115 nm to 63 nm after microwave irradiation up to 1573 K.

A solid-state reaction route-based LiTi 2 À x Eu x (PO 4) 3 was phosphor synthesized for the firs... more A solid-state reaction route-based LiTi 2 À x Eu x (PO 4) 3 was phosphor synthesized for the first time to evaluate its lumi-nescence performance by excitation, emission and lifetime (τ) measurements. The LiTi 2 À x Eu x (PO 4) 3 phosphor was excited at λ exci. = 397 nm to give an intense orange–red (597 nm) emission attributed to the 5 D 0 → 7 F 1 magnetic dipole (ΔJ = ±1) transition and red (616 nm) emission (5 D 0 → 7 F 2), which is an electric dipole (ΔJ = ±2) transition of the Eu 3+ ion. Beside this, excitation and emission spectra of host LiTi 2 (PO 4) 3 powder were also reported. The effect of Eu 3+ concentration on luminescence characteristics was explained from emission and lifetime profiles. Concentration quenching in the LiTi 2 À x Eu x (PO 4) 3 phosphor was studied from the Dexter's model. Dipole–quadrupole interaction is found to be responsible for energy transfer among Eu 3+ ions in the host lattice. The LiTi 2 À x Eu x (PO 4) 3 phosphor displayed a reddish-orange colour realized from a CIE chromaticity diagram. We therefore suggest that this new phosphor could be used as an optical material of technological importance in the field of display devices.