Вплив катіонного заміщення на електричну провідність суперіонної кераміки на основі мікрокристалічних порошків (Cu1-xAgx)7SiS5I

Abstract

Керамічні зразки на основі мікрокристалічних порошків (Cu1−xAgx)7SiS5I були виготовлені шляхом їх пресування при тиску ∼ 400 МПа та послідуючого відпалу при температурі 973 K протягом 36 годин. Дослідження електропровідності керамік на основі твердих розчинів (Cu1−xAgx)7SiS5I проводилися методом імпедансної спектроскопії в частотному діапазоні від 10 Гц до 2×106 Гц та температурному інтервалі 292–383 К. Встановлено, що при збільшенні вмісту атомів срібла в керамічних зразках на основі (Cu1−xAgx)7SiS5I іонна компонента електричної провідності нелінійно збільшується, електронна – нелінійно зменшується, а їх відношення – нелінійно зростає і для Ag7SiS5I перевищує 3000.

Керамические образцы на основе микрокристаллических порошков (Cu1−xAgx)7SiS5I были изготовлены путем их прессования при давлении ∼ 400 МПа и последующего отжига при температуре 973 K в течение 36 часов. Исследование электропроводности керамик на основе твердых растворов (Cu1−xAgx)7SiS5I проводились методом импедансной спектроскопии в частотном диапазоне от 10 Гц до 2 × 106 Гц и температурном интервале 292–383 К. Установлено, что при увеличении содержания атомов серебра в керамических образцах на основе (Cu1−xAgx)7SiS5I ионная компонента электрической проводимости нелинейно увеличивается, электронная – нелинейно уменьшается, а их отношение – нелинейно возрастает и для Ag7SiS5I превышает 3000. Ключевые слова:

Purpose. The purpose of this research was to prepare the superionic ceramics, to study the frequency and temperature dependences of electrical conductivity as well as to investigate the compositional behavior of the total electrical conductivity, the ionic and electronic components of the electrical conductivity, and their activation energies for ceramics based on (Cu1−xAgx)7SiS5I solid solutions. Methods. For preparing the ceramic samples the compounds based on Cu7SiS5I, Ag7SiS5I and (Cu1−xAgx)7SiS5I (x = 0.25, 0.5, 0.75) solid solutions were synthesized. Then, the microcrystalline powders were obtained by grinding the synthesized compounds in an agate mortar to a sizes of ∼ 10–50 μm. Pressing of the samples was performed at a pressure of ∼ 400 MPa, and annealing was carried out at a temperature of 973 K during 36 hours. Ceramic samples based on (Cu1−xAgx)7SiS5I solid solutions were obtained in the form of disks with a diameter of 8 mm and a thickness of 3-4 mm. Investigations of the electrical conductivity of ceramics based on (Cu1−xAgx)7SiS5I (x = 0.25, 0.5, 0.75, 1) was performed by the method of impedance spectroscopy, in frequency (10 Hz – 2×106 Hz) and temperature (292 – 383K) ranges using the high-precision LCR meter Keysight E4980A and AT-2818. Measurement was carried out by a two-electrode method on blocking gold contacts, which were applied by chemical precipitation from solutions. Results. The frequency dependences of the total electrical conductivity showed an increase of conductivity with increasing frequency for all ceramic samples. It has been established that with increasing Ag content in ceramics based on (Cu1−xAgx)7SiS5I, the total electrical conductivity is growing non-linearly at 100 kHz. Nyquist diagrams were constructed and their detailed analysis was carried out using an electrodes-equivalent circuit. Using the Nyquist diagrams and the electrodes-equivalent circuit, the contributions of the ionic and electronic components to the total electrical conductivity were separated. It is shown that with silver content increase the ionic conductivity nonlinearly increases while the electronic conductivity nonlinearly decreases. The analysis of the compositional dependence of the ratio of the ionic conductivity to the electronic one showed that due to the cation substitution of Cu+ → Ag+ the ratio nonlinearly increases. Conclusions. Superionic ceramics based on (Cu1−xAgx)7SiS5I were prepared. Measurements of electrical conductivity of ceramic samples by means of impedance spectroscopy in the frequency range from 10 Hz to 2 × 106 Hz and in the temperature range 292 - 383 K were carried out. Frequency dependencies of total electrical conductivity were obtained. The influence of the cation substitution of Cu+ → Ag+ on the total electrical conductivity, on the electronic and ionic components of the conductivity of ceramics based on (Cu1−xAgx)7SiS5I was studied on the basis of compositional dependence.