Effect of Boron Addition on the Dielectric Properties of Giant Dielectric CaCu₃Ti₄O₁₂

Abstract

The recently discovered giant dielectric CaCu 3 Ti 4 O 12 (CCTO)

Low temperature sintering of CCTO using P2O5 as a sintering aid

“…The dielectric loss increases without any peak at high frequency. This is a signature of stray inductance of the contacts and leads [4]. Incidentally, increasing the P 2 O 5 concentration beyond 1% deteriorates the dielectric properties of the material (k value for 3% and 5% P 2 O 5 incorporated samples are 870 and 470 at 1 kHz, respectively) which is in agreement with the decreasing trend of bulk density with P 2 O 5 content.…”

“…2 represents the variation of bulk density of CCTO with P 2 O 5 addition after sintering at 1000 8C for 40 h. It can be seen that the density is maximum for 1% P 2 O 5 incorporated sample and the density increases with soaking time. It is expected that P 2 O 5 forms a glassy phase [4] and helps in liquid phase sintering of CCTO. For liquid phase sintering there is an optimum amount of liquid phase [11] above which the densification decreases as has been found in the present case.…”

“…Incidentally, increasing the P 2 O 5 concentration beyond 1% deteriorates the dielectric properties of the material (k value for 3% and 5% P 2 O 5 incorporated samples are 870 and 470 at 1 kHz, respectively) which is in agreement with the decreasing trend of bulk density with P 2 O 5 content. The 1% P 2 O 5 incorporated samples sintered at 1000 8C for 40 h show very high dielectric constant value (%40,000) at 1 kHz at room temperature, which is comparable to or better than higher temperature (>1000 8C) sintered CCTO with additives like SiO 2 , [10] B 2 O 3 , [11] BaO-B 2 O 3 -SiO 2 glass [4]. Longer soaking time produces more oxygen vacancies and space charge [16] leading to a very high dielectric constant value.…”

“…CaCu 3 Ti 4 O 12 (CCTO) is known to have a giant dielectric permittivity [1][2][3][4] of >10 4 over a wide temperature range from %100 to 400 K. The possible origin of such a high dielectric constant is still controversial [1,2,5] though the generally accepted mechanism is an internal barrier layer capacitor model, which consists of semiconducting grains and insulating domain or grain boundaries. Presently, the work on CCTO is mostly directed towards decreasing its dissipation factor and further raising its dielectric constant by using different dopants [6][7][8][9] and also lowering its sintering temperature (by adding different sintering aids) [4,[10][11][12] so that, other than energy saving, low-cost electrodes (Ag-Pd or base metal) can be used for making multilayer capacitors using CCTO. Normally, CCTO needs a processing temperature of 1100 8C and above for densification [13].…”

Charge compensation, electrical and dielectric behavior of lanthanum doped CaCu3Ti4O12

“…Although, CCTO possesses giant dielectric constant, the dielectric losses are too high to commercialize it. Number of attempts has been made to decease tan ı by various compositional modifications such as Cr 2 O 3 -doped CCTO [7], ZrO 2 -doped CCTO [8], CCTO/CaTiO 3 composite [9], B 2 O 3 doped CCTO [10], TiO 2 -rich CCTO [11,12] and La substitution on Cu sites in CCTO [13] have been reported to be effective in reducing the dielectric loss and still maintaining high dielectric constant. In a study by Cheng et al [14], it was shown that in La doped CaCu 3 Ti 4 O 12 , Ca site is completely substituted by La without influencing the phase transition.…”