ESTUDO DAS PROPRIEDADES ELETRICAS DA MATRIZ CERÂMICA Sr3V2O8 (SVO) ADICIONADA DE Bi2O3 PARA APLICAÇÕES EM DISPOSITIVOS DE MICROONDAS

Abstract

In this work, the structural and dielectric properties of the Sr3V2O8 (SVO) ceramic matrix with addition of bismuth oxides (SVON, N = 0, 10, 20,30 and 40 wt% of Bi2O3) were investigated as a function of frequency and temperature for possible uses in radio frequency and microwave device applications (dielectric resonators). Our interest was to obtain ceramic dielectrics with high dielectric constant, combined with low dielectric losses and thermal stability. In the measurements performed at room temperature at 27°C, we obtained high values of the dielectric constant (ε') with low loss values (tanδ) in 1 MHz radio frequency measurements; for example, in the SVO and SVO40 samples, where consecutive values of dielectric constants and losses of ε'= 112, tanδ = 10-2 and ε' = 75 , tanδ = 6x10-3., were obtained. With the variation of temperature and fixed frequency of 1 kHz, we obtained high dielectric constant values around 730 to 1300 at various temperatures. The study revealed that SVON compounds have giant dielectric constants at various temperatures. The measurements temperature coefficient of capacitance (TCC) showed that the thermal capacitive stability can be reached, at 1MHz by increasing the addition level of Bi2O3 up to TCC  0ppm/°C. With SVO we have obtained a TCC = -0,55 ppm/°C that doped with 40% of Bi2O3 moved up for TCC = -0.053 ppm/°C. The Measurements in the microwave range of 4-6 GHz were obtained using the Hakki-Coleman method, using TE011 mode. For the SVO, sintering at 1050°C for 4h, we obtained a product of quality factor for the resonance frequency (Q x f) equal to 13.232 GHz and a dielectric permittivity equal to 14,81. In this study we obtained a ceramic SVON useful for the development of ceramic capacitors, thermistors NTC and radio-frequency device, microwave devices and dielectric resonator developments.