Origin of the electronic conductivity in la2cuo4 synthesized by solution combustion method
Source
Indian Institute of Technology, Gandhinagar
Date Issued
2016-01-01
Author(s)
Arora, Payal
Abstract
Lanthanum cuprate (La2CuO4) is a well-known stable layered perovskite oxide with K2NiF4
structure, consisting perovskite layers with alternating rock-salt layers. In this thesis, we reported
the synthesis of La2CuO4 by solution combustion technique using urea as a fuel. The assynthesized
and calcined La2CuO4 were characterized by X-ray diffraction technique. Compound
La2CuO4 was calcined at different temperature ranges 900oC, 950oC, 1000oC, 1050oC and
1100oC. Conductivity of all compound were measured using four-probe technique. Assynthesized
La2CuO4 doesn’t show conductivity and other compounds are conducting with a
different extent. Highest conductivity was observed in La2CuO4 at 1000oC calcination
temperature. Conductivity probe - atomic force microscopy (CP-AFM) studies of three samples
of compound La2CuO4 calcined at 900oC, 1000oC and 1100oC were performed. CP-AFM results
shows that the grain size of La2CuO4 crystallites increases with the increase of heat treatment
temperature from 900°C to 1100°C. TUNA current micrographs of compound La2CuO4 in CPAFM
concludes conductivity is not properly channelized and present in the grain boundaries.
Also, CP-AFM give assurance of maximum conductivity of La2CuO4 calcined at 1000oC by
looking in TUNA current micrograph. For identifying the reason of conductivity in La2CuO4, we
again synthesized compound with different precursor amounts. On increasing amount of urea in
La2CuO4, increase in conductivity was observed in four-probe technique. Thus, Carbon is
responsible for conductivity in La2CuO4. Also, for identifying change in size of lattice, we were
focused on shifting of peak by adding NaCl. The shifting of highest intensity peak in La2CuO4 at
1000oC towards higher diffraction angle showing compression in lattice size and supports the
highest conductivity result at that temperature by four-probe and CP-AFM. Shrinkage in lattice
size helps in attaining the conductivity in the temperature range of 900-1000oC. Above 1000oC,
lattice size again expands and hence the decrease in the conductivity.
structure, consisting perovskite layers with alternating rock-salt layers. In this thesis, we reported
the synthesis of La2CuO4 by solution combustion technique using urea as a fuel. The assynthesized
and calcined La2CuO4 were characterized by X-ray diffraction technique. Compound
La2CuO4 was calcined at different temperature ranges 900oC, 950oC, 1000oC, 1050oC and
1100oC. Conductivity of all compound were measured using four-probe technique. Assynthesized
La2CuO4 doesn’t show conductivity and other compounds are conducting with a
different extent. Highest conductivity was observed in La2CuO4 at 1000oC calcination
temperature. Conductivity probe - atomic force microscopy (CP-AFM) studies of three samples
of compound La2CuO4 calcined at 900oC, 1000oC and 1100oC were performed. CP-AFM results
shows that the grain size of La2CuO4 crystallites increases with the increase of heat treatment
temperature from 900°C to 1100°C. TUNA current micrographs of compound La2CuO4 in CPAFM
concludes conductivity is not properly channelized and present in the grain boundaries.
Also, CP-AFM give assurance of maximum conductivity of La2CuO4 calcined at 1000oC by
looking in TUNA current micrograph. For identifying the reason of conductivity in La2CuO4, we
again synthesized compound with different precursor amounts. On increasing amount of urea in
La2CuO4, increase in conductivity was observed in four-probe technique. Thus, Carbon is
responsible for conductivity in La2CuO4. Also, for identifying change in size of lattice, we were
focused on shifting of peak by adding NaCl. The shifting of highest intensity peak in La2CuO4 at
1000oC towards higher diffraction angle showing compression in lattice size and supports the
highest conductivity result at that temperature by four-probe and CP-AFM. Shrinkage in lattice
size helps in attaining the conductivity in the temperature range of 900-1000oC. Above 1000oC,
lattice size again expands and hence the decrease in the conductivity.
Subjects
Lanthanum cuprate
X-ray diffraction technique