Structural, magnetic and dielectric properties of La2−xCaxNiO4+δ (x=0, 0.1, 0.2, 0.3)

Ultrafast dynamics of vibrational symmetry breaking in a charge-ordered nickelate

“…augmented plane-wave method as implemented in the WIEN2k (35) package and a k-mesh size of 11 x 11 x 7 for the self-consistent calculations. The lattice is based on the undoped I4/mmm structure (36). To determine the phonon dispersion, we employed Phonopy to calculate the spectra based on the finite displacement method for a 2x2x1 supercell (37).…”

Synthesis of Sr1+2xLa1‐2xFe1‐xNbxO4 (x=0, 0.1, 0.3, and 0.5) by Sol‐gel Method: Structural, Magnetic, and Dielectric Properties

“…[41] The values of the dielectric constant at 1kHz of this sample are higher than that of La 2-x Ca x NiO 4 + δ (x = 0, 0.1, 0.2, 0.3) that have been measured in previous studies. [25] The value of ac conductivity (σac = ωεε'',w here ω = 2πfi s angular frequency, ε is permittivity of free space, and ε'' is the imaginary part of the dielectric constant) as af unction of frequency for samples with x = 0, 0.1, and 0.3 reflects similar behavior to the dielectric constant values, as can been seen from Figure 6. Conductivity clearly decreases with decreasing frequency and then becomes nearly constant at ac ertain frequency.…”

“…However, at ah igher frequency (100 kHz) these values decrease to 1.16 ×10 4 ,9 .91 × 10 3 ,a nd 5.29 ×10 3 .T his behavior has been observed in many compounds and has been explained by dipole relaxation in which the dipole is able to follow the low frequencies but unable to follow at higher frequencies. [25,[38][39][40] Moreover, pores, voids, interstitial and vacancy defects, dislocations, grain boundaries, and dipoles also contribute to dielectric properties in our samples. It can be seen that the value of the dielectric constant decreases as x increases.…”

“…In recent years, semiconducting materials based on the RP phase have been developed as giant dielectric materials. [25] Since there is no information about the dielectric properties for this compound, this will provide useful data. We also investigated ac conductivity to provide information related to the phenomenon of surface conduction and its response to temperature and frequency.…”

Ruddlesden-Popper phase A2BO4 oxides: Recent studies on structure, electrical, dielectric, and optical properties

“…NiO is lower than that of some Sr substituted nickelate ceramics, but still it is not suitable for the practical applications due to high dielectric loss [127]. Shi et al [128] have reported colossal dielectric properties in La Ca NiO . Among all the samples, at 1 MHz La .…”