Improvement in dielectric properties of Al2O3-doped Li0.30Cr0.02Ni0.68O ceramics

Influence of Cr doping on structure and dielectric properties of LixCryNi1−x−yO ceramics

“…It was also found that the grain size decreased with increasing Cr concentration. The reduction of grain size was consistent with the results in other studies [7,8]. This was possibly due to the existence of secondary phases at the grain boundaries, leading to a suppression of grain growth.…”

“…Recently, CaCu 3 Ti 4 O 12 (CCTO) [1][2][3][4][5] and (A, B)-codoped NiO systems with the formula A x B y Ni 1 À x À y O [6][7][8][9][10][11][12][13][14][15][16][17][18][19][20][21][22][23][24] have been actively investigated due to their extraordinarily high dielectric constants (ε r $ 10 4 -10 5 ) with weak temperature and frequency dependence. It has been widely thought that the boundary layer capacitors (BLCs) model is the most likely explanation of their dielectric behavior.…”

“…This is responsible for the high dielectric constant of such material systems, which can be tuned by changing the elements, A and B, in A x B y Ni 1 À x À y O materials. Numerous authors reported tuned compositions of A (i.e., Li [6][7][8][9][10][11][12][13], Na [14], K [19]) and B (i.e., Al [7,17], Si [22], Ti [6,9,10,15,18], W [13], V [13,20], Cr [8,21], Co [11], Zr [12], Fe [16], Pr [23], Ta [24]). NiO is a Mott-Hubbard insulator at room temperature.…”

“…As the result, more charges accumulated at the grain boundary, resulting in its huge dielectric constant. To obtain a huge dielectric constant and a low loss tangent, Cr was used as a dopant in LiNiO lattice with the stoichiometry of Li 0.30 Cr 0.02 -Ni 0.68 O as reported by our group [8,21]. Huge dielectric constants (ε r $ 10 4 -10 5 ) were observed in these materials.…”

Enhanced Dielectric Properties and High-Temperature Microwave Absorption Performance of Zn-Doped Al2O3 Ceramic

“…This can be explained by the substitution limit. Owing to the different valence and ionic radius of Zn 2+ (0.074 nm) 24 and Al 3+ (0.0535 nm), 25 the content of Al 3+ that can be substituted by Zn 2+ is limited. When the doping content is higher than this substitution limit, the excess Zn 2+ will combine with Al 3+ and O 2À to form ZnAl 2 O 4 phase.…”