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Papers by M. Ijjaali

Research paper thumbnail of Education: Essential Approach for a Better Water Management

Procedia - Social and Behavioral Sciences, 2015

Research paper thumbnail of Synthèse et propriétés complexantes de nouveaux systèmes hétérocycliques dérivant de la 1,5-benzodiazépine-2,4-dione

Research paper thumbnail of A neutron diffraction and Mossbauer effect study of the (FeO2)n ferromagnetic sheets in antiferromagnetic alpha -Fe2(PO4)O

The substitution of silicon for iron in Nd2Fe~7 strongly raises the Curie temperature but leads t... more The substitution of silicon for iron in Nd2Fe~7 strongly raises the Curie temperature but leads to a reduction in the unit cell volume. Refinement of the neutron-diffraction pattern for Nd2Fel2.91Si4.09 indicates that silicon preferentially occupies the 18h site in the Nd2Fet~ structure, the site with the most neodymium near neighbors. This occupation is surprising because conventional arguments would suggest that replacement of iron on the 6c site, which has a very short iron to near-neighbor iron bond length, would yield an increase in the Curie temperature.

Research paper thumbnail of Semiconducting properties of CoO thin films

Research paper thumbnail of Electrical properties of Cr-doped CoO

This paper reports the results of the electrical conductivity measurements for polycrystalline sp... more This paper reports the results of the electrical conductivity measurements for polycrystalline specimens of undoped and Cr-doped CoO in the ranges of p(O2) (10−5 – 105 Pa) and temperature (1223 – 1373 K). The experimental data are considered in terms of the effect of Cr on semiconducting properties of CoO. It is shown that Cr results in a decrease of the reciprocal of the p(O2) exponent of electrical conductivity, however, the obtained experimental values are substantially lower than those predicted by defect chemistry. The activation energy of the electrical conductivity remains independent of p(O2) and Cr content (at the level of about 0.5 eV) except strongly reduced CoO, at p(O2)=2.10−4 Pa, of which the activation energy is substantially higher. Thermopowervs p(O2) exhibits maximum at p(O2)=10 Pa (except of thermopower data for Cr-doped CoO at the highest temperature). The experimental data are considered in terms of the effect of both p(O2) and Cr on semiconducting properties.

Research paper thumbnail of Stability, structure refinement, and magnetic properties of β-Fe2(PO4)O

Journal of Solid State Chemistry, 1990

ABSTRACT

Research paper thumbnail of Crystal Structure Refinement and Magnetic Properties of Fe4(P2O7)3 Studied by Neutron Diffraction and Mössbauer Techniques

Journal of Solid State Chemistry, 2002

Research paper thumbnail of Electrical properties of Nb-doped BaTiO3

Journal of Physics and Chemistry of Solids, 2001

This paper reports the results of the electrical conductivity measurements for Nb-doped BaTiO 3 c... more This paper reports the results of the electrical conductivity measurements for Nb-doped BaTiO 3 ceramics in the temperature range 1073±1373 K in both oxidizing and reducive atmospheres. The electrical conductivity was also applied to monitor the formation of Nb-doped BaTiO 3 . It is shown that the solid state reaction for the system BaTiO 3 ±Nb 2 O 3 takes place at 1573 K, but annealing at 1623 K is required to produce specimen of reproducible electrical properties. The solubility limit of Nb in stoichiometric BaTiO 3 Ba=Ti 1 at 1573 K in air is 5 at%. The p(O 2 ) exponent of the electrical conductivity was determined 1=n s 21=3:9: This exponent is consistent with the defect disorder model of Nb-doped BaTiO 3 derived assuming that ionic charge compensation prevails. The activation energy of the electrical conductivity for Nb-doped BaTiO 3 depends on both p(O 2 ) and Nb content. q

Research paper thumbnail of Effect of oxygen activity on Nb solubility in BaTiO3

Journal of Physics and Chemistry of Solids, 2001

This paper describes the effect of oxygen partial pressure on Nb solubility in polycrystalline Ba... more This paper describes the effect of oxygen partial pressure on Nb solubility in polycrystalline BaTiO3 at 1673K. It was found that an increase of p(O2) in the gas phase results in an increased Nb solubility in BaTiO3. Annealing of polycrystalline BaTiO3, covered with a thin layer of NbCl5, in air at 1573K results in Nb incorporation to the level of

Research paper thumbnail of Kinetics of Nb incorporation into barium titanate

Journal of Physics and Chemistry of Solids, 2001

The diffusion coef®cient of Nb in BaTiO 3 single crystal was determined from the Nb diffusion pro... more The diffusion coef®cient of Nb in BaTiO 3 single crystal was determined from the Nb diffusion pro®le in the temperature range 1530±1723 K in air. The Arrhenius plot of the obtained diffusion data indicates that there is a change in the diffusion mechanism at 1626 K. At 1530 K these data are consistent with the chemical diffusion coef®cient of Nb-doped BaTiO 3 . It was found that the transport in Nb at 1530 K and above this temperature occurs according to a different mechanism. Below 1481 K the process of Nb incorporation into BaTiO 3 is substantially retarded. q

Research paper thumbnail of Education: Essential Approach for a Better Water Management

Procedia - Social and Behavioral Sciences, 2015

Research paper thumbnail of Synthèse et propriétés complexantes de nouveaux systèmes hétérocycliques dérivant de la 1,5-benzodiazépine-2,4-dione

Research paper thumbnail of A neutron diffraction and Mossbauer effect study of the (FeO2)n ferromagnetic sheets in antiferromagnetic alpha -Fe2(PO4)O

The substitution of silicon for iron in Nd2Fe~7 strongly raises the Curie temperature but leads t... more The substitution of silicon for iron in Nd2Fe~7 strongly raises the Curie temperature but leads to a reduction in the unit cell volume. Refinement of the neutron-diffraction pattern for Nd2Fel2.91Si4.09 indicates that silicon preferentially occupies the 18h site in the Nd2Fet~ structure, the site with the most neodymium near neighbors. This occupation is surprising because conventional arguments would suggest that replacement of iron on the 6c site, which has a very short iron to near-neighbor iron bond length, would yield an increase in the Curie temperature.

Research paper thumbnail of Semiconducting properties of CoO thin films

Research paper thumbnail of Electrical properties of Cr-doped CoO

This paper reports the results of the electrical conductivity measurements for polycrystalline sp... more This paper reports the results of the electrical conductivity measurements for polycrystalline specimens of undoped and Cr-doped CoO in the ranges of p(O2) (10−5 – 105 Pa) and temperature (1223 – 1373 K). The experimental data are considered in terms of the effect of Cr on semiconducting properties of CoO. It is shown that Cr results in a decrease of the reciprocal of the p(O2) exponent of electrical conductivity, however, the obtained experimental values are substantially lower than those predicted by defect chemistry. The activation energy of the electrical conductivity remains independent of p(O2) and Cr content (at the level of about 0.5 eV) except strongly reduced CoO, at p(O2)=2.10−4 Pa, of which the activation energy is substantially higher. Thermopowervs p(O2) exhibits maximum at p(O2)=10 Pa (except of thermopower data for Cr-doped CoO at the highest temperature). The experimental data are considered in terms of the effect of both p(O2) and Cr on semiconducting properties.

Research paper thumbnail of Stability, structure refinement, and magnetic properties of β-Fe2(PO4)O

Journal of Solid State Chemistry, 1990

ABSTRACT

Research paper thumbnail of Crystal Structure Refinement and Magnetic Properties of Fe4(P2O7)3 Studied by Neutron Diffraction and Mössbauer Techniques

Journal of Solid State Chemistry, 2002

Research paper thumbnail of Electrical properties of Nb-doped BaTiO3

Journal of Physics and Chemistry of Solids, 2001

This paper reports the results of the electrical conductivity measurements for Nb-doped BaTiO 3 c... more This paper reports the results of the electrical conductivity measurements for Nb-doped BaTiO 3 ceramics in the temperature range 1073±1373 K in both oxidizing and reducive atmospheres. The electrical conductivity was also applied to monitor the formation of Nb-doped BaTiO 3 . It is shown that the solid state reaction for the system BaTiO 3 ±Nb 2 O 3 takes place at 1573 K, but annealing at 1623 K is required to produce specimen of reproducible electrical properties. The solubility limit of Nb in stoichiometric BaTiO 3 Ba=Ti 1 at 1573 K in air is 5 at%. The p(O 2 ) exponent of the electrical conductivity was determined 1=n s 21=3:9: This exponent is consistent with the defect disorder model of Nb-doped BaTiO 3 derived assuming that ionic charge compensation prevails. The activation energy of the electrical conductivity for Nb-doped BaTiO 3 depends on both p(O 2 ) and Nb content. q

Research paper thumbnail of Effect of oxygen activity on Nb solubility in BaTiO3

Journal of Physics and Chemistry of Solids, 2001

This paper describes the effect of oxygen partial pressure on Nb solubility in polycrystalline Ba... more This paper describes the effect of oxygen partial pressure on Nb solubility in polycrystalline BaTiO3 at 1673K. It was found that an increase of p(O2) in the gas phase results in an increased Nb solubility in BaTiO3. Annealing of polycrystalline BaTiO3, covered with a thin layer of NbCl5, in air at 1573K results in Nb incorporation to the level of

Research paper thumbnail of Kinetics of Nb incorporation into barium titanate

Journal of Physics and Chemistry of Solids, 2001

The diffusion coef®cient of Nb in BaTiO 3 single crystal was determined from the Nb diffusion pro... more The diffusion coef®cient of Nb in BaTiO 3 single crystal was determined from the Nb diffusion pro®le in the temperature range 1530±1723 K in air. The Arrhenius plot of the obtained diffusion data indicates that there is a change in the diffusion mechanism at 1626 K. At 1530 K these data are consistent with the chemical diffusion coef®cient of Nb-doped BaTiO 3 . It was found that the transport in Nb at 1530 K and above this temperature occurs according to a different mechanism. Below 1481 K the process of Nb incorporation into BaTiO 3 is substantially retarded. q

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