2 research outputs found
The Role of Structural and Compositional Heterogeneities in the Insulator-to-Metal Transition in Hole-Doped APd<sub>3</sub>O<sub>4</sub> (A = Ca, Sr)
The
cubic semiconducting compounds APd<sub>3</sub>O<sub>4</sub> (A = Ca,
Sr) can be hole-doped by Na substitution on the A site and driven
toward more conducting states. This process has been followed here
by a number of experimental techniques to understand the evolution
of electronic properties. While an insulator-to-metal transition is
observed in Ca<sub>1–<i>x</i></sub>Na<sub><i>x</i></sub>Pd<sub>3</sub>O<sub>4</sub> for <i>x</i> ≥ 0.15, bulk metallic behavior is not observed for Sr<sub>1–<i>x</i></sub>Na<sub><i>x</i></sub>Pd<sub>3</sub>O<sub>4</sub> up to <i>x</i> = 0.20. Given the very
similar crystal and (calculated) electronic structures of the two
materials, the distinct behavior is a matter of interest. We present
evidence of local disorder in the A = Sr materials through the analysis
of the neutron pair distribution function, which is potentially at
the heart of the distinct behavior. Solid-state <sup>23</sup>Na nuclear
magnetic resonance studies additionally suggest a percolative insulator-to-metal
transition mechanism, wherein presumably small regions with a signal
resembling metallic NaPd<sub>3</sub>O<sub>4</sub> form almost immediately
upon Na substitution, and this signal grows monotonically with substitution.
Some signatures of increased local disorder and a propensity for Na
clustering are seen in the A = Sr compounds
The Role of Structural and Compositional Heterogeneities in the Insulator-to-Metal Transition in Hole-Doped APd<sub>3</sub>O<sub>4</sub> (A = Ca, Sr)
The
cubic semiconducting compounds APd<sub>3</sub>O<sub>4</sub> (A = Ca,
Sr) can be hole-doped by Na substitution on the A site and driven
toward more conducting states. This process has been followed here
by a number of experimental techniques to understand the evolution
of electronic properties. While an insulator-to-metal transition is
observed in Ca<sub>1–<i>x</i></sub>Na<sub><i>x</i></sub>Pd<sub>3</sub>O<sub>4</sub> for <i>x</i> ≥ 0.15, bulk metallic behavior is not observed for Sr<sub>1–<i>x</i></sub>Na<sub><i>x</i></sub>Pd<sub>3</sub>O<sub>4</sub> up to <i>x</i> = 0.20. Given the very
similar crystal and (calculated) electronic structures of the two
materials, the distinct behavior is a matter of interest. We present
evidence of local disorder in the A = Sr materials through the analysis
of the neutron pair distribution function, which is potentially at
the heart of the distinct behavior. Solid-state <sup>23</sup>Na nuclear
magnetic resonance studies additionally suggest a percolative insulator-to-metal
transition mechanism, wherein presumably small regions with a signal
resembling metallic NaPd<sub>3</sub>O<sub>4</sub> form almost immediately
upon Na substitution, and this signal grows monotonically with substitution.
Some signatures of increased local disorder and a propensity for Na
clustering are seen in the A = Sr compounds