Miniaturized drives and speed of the computer transfer more focus into the high-temperature resistant parts, the capacitor must be able to work at 150℃ or even 200℃ in the future. However, the application of PbTiO3-BaTiO3 composite multilayer ceramic capacitor is not desirable, the first reason is 1¾ toxicity, the second one is that easy to decompose in low oxygen partial pressure, and Ni metal electrode will form into low melting point alloy with it. The same problem also appears in BiTiO3 doped by Bi2O3 base solid solution. The ideal new materials require the phase transition temperature is between -50 ℃ ~250 ℃, without PbO or Bi2O3, containing relatively common and inexpensive raw materials.
Recently, domestic and foreign researchers found that a number of tantalates with tungsten bronze structure having high dielectric constant (> 100) and low dielectric loss, is expected to be the dielectric materials with temperature stability being used in multilayer ceramic capacitors. The ceramic dielectric constant ε r is between 127~175, dielectric loss tan σ is less than 0.009 at 1MHz, the dielectric constant and temperature coefficient τ ε is between -7¾~-2500ppm / ℃. But the dielectric constant and temperature coefficient of these tantalates with tungsten bronze structure are too large, the dielectric constant is too low, thus the practical applications are limited.
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