Microstructures and electrical responses of pure and chromium-doped CaCu3Ti4O12 ceramics

Giant dielectric permittivity and electronic structure in (Al+Sb)co-doped TiO2 ceramics

“…The examples of giant-dielectric materials are CaCu 3 Ti 4 O 12 and related compounds [1][2][3][4][5][6][7][8], CuO [9], Ln 2Àx Sr x NiO 4 (Ln = Nd, La, Sm) [10][11][12][13], (M,N)-doped NiO systems (M = Li, Na, K and N = Ti, Al, Si, Ta) [14][15][16][17], AFe 1/2 B 1/2 O 3 (A = Ba, Sr, Ca; B = Nb, Ta, Sb) [18,19], and LuFe 2 O 4 [20] ceramics. Unfortunately, tand values of these materials are still larger than 0.04 at 1 kHz which is the standard value for capacitor applications.…”

“…Unfortunately, tand values of these materials are still larger than 0.04 at 1 kHz which is the standard value for capacitor applications. CaCu 3 Ti 4 O 12 ceramics have shown to be the most actively giant-dielectric materials in recent years [1][2][3][4][5]21,22]. However, rather large value of tand is still existed.…”

A novel approach to achieve high dielectric permittivity and low loss tangent in CaCu3Ti4O12 ceramics by co-doping with Sm3+ and Mg2+ ions

“…CaCu 3 Ti 4 O 12 (CCTO) is one of the most interesting giant dielectric materials and has been intensively investigated due to its potential applications and for academic reasons [1][2][3][4][5][6][7]. CCTO can exhibit very high dielectric permittivity ( ) values, in the range of 10 3 -10 5 (at room temperature and frequencies <10 5 Hz).…”

“…Presently, there are many methods available for enhancing these resistances. These include (1) changing Ca 2+ and Cu 2+ molar ratios to produce CCTO/CaTiO 3 (CTO) composites [17], (2) increasing the molar concentration of Ti in CCTO to produce CCTO/TiO 2 composites [18], (3) sintering or annealing CCTO in an oxidizing atmosphere to fill oxygen vacancies at GBs [3], (4) deliberately adding or creating a low-tan␦ second phase [19], (5) using new preparation methods [10,16], (6) reducing the grain size to increase the density of GB layers [11], and, (7) substitution of suitable metal ions into CCTO to intrinsically improve the electrical properties of GBs [9,[20][21][22][23] According to these methods, changes in the macroscopic properties of the GBs to decrease dc and tan␦ can be divided into two groups, i.e., geometric and intrinsic factors. The former controls the microstructure to obtain a fine grained ceramic microstructure with small grain sizes.…”

Effect of Annealing in O2 and Mechanisms Contributing to the Overall Loss Tangent of CaCu3Ti4O12 Ceramics

“…This is another important issue needing investigation to realize the goal of application of CCTO ceramics. Many investigations have indicated that the high directcurrent (DC) conductivity (r dc ) of CCTO ceramics primary affects the value of tan d. 15,16,27,28 In the case of high-r dc dielectric ceramics or lossy dielectric materials such as La 2Àx Sr x NiO 4 and codoped NiO ceramics, the effect of DC conduction upon tan d values (tan d > 10 at 10 3 Hz) can be dominant at higher frequencies (>10 4 Hz). 29,30 However, for CCTO and related ceramic compounds, this is a parameter that has a remarkable influence upon the value of tan d at frequencies lower than 10 3 Hz.…”