Propiedades de transporte de cerámicas Bicuvox dopadas

Abstract

.5-δ a temperaturas superiores a 500K es ligeramente menor que la correspondiente a BICUVOX.10 no dopada, pero las propiedades de transporte en el rango de temperaturas 370-450K son similares. Dopando BICUVOX.10 con praseodimio produce la formaci-n de fases secundarias y la reducci-n de la conductividad y la expansi-n tŽrmica de las muestras cer ‡micas. El noemero de transporte del i-n sin ox'geno de fases con un contenido en tierra rara moderado como dopante (x ≤ 0.10) varia en el rango 0.90-0.99 a 780-910k y disminuye con el aumento de la temperatura. Los coeficientes de expansi-n tŽrmicos calculados a partir de los datos dilatomŽtricos para cer ‡micas

Phase Transitions and Transport Properties of the Bismuth Vanadate-Based (Bi,La)4(V,Zr)2O11-zCeramics

“…In compositions with higher y values, parameter a increases slightly, parameter b decreases slightly, while parameters c and V do not change with increasing concentration of La 3+ cations. These results are consistent with the data obtained earlier for Zror La-doped bismuth vanadate solid solutions [6,9,10,[13][14][15][16][17][18][19].…”

“…It is worse noting that the temperature hysteresis of β-γ phase transition increases from 36 K (y = 0.0) to 60 K (y = 0.08), always remaining smaller than the temperature hysteresis of α-β transition both in the samples with x, y = 0.0 (84 K) and with x = 0.05, y = 0.0 (98 K). It is believed that the main cause of such large temperature hysteresis of the α-β phase transition may be connected with the oxygen vacancies orderingdisordering in vanadium layers of the crystal structure and their "pinning" at the ferroelectric domain walls as well [18]. Samples with x > 0.1 which according to the X-ray data, have the ordered tetragonal γ -structure at the room temperature are characterized by the reversible γ -γ "order-disorder" phase transition at approximately 700 K. In the dielectric permittivity ε(t) and dielectric loss tan δ(t) versus temperature plots, peaks, corresponding to ferroelectric-paraelectric α-β phase transition, were observed only for the samples with x ≤ 0.05, y ≤ 0.05 [14] (Fig.…”

“…The parent bismuth vanadate compound undergoes phase transitions between α and β polymorphous modifications at approximately 700 K and between β-and tetragonal γ-phase at approximately 850 K [3][4][5]. Composition modifications by substitution of different valency cations for V 5+ and/or Bi 3+ cations were aimed at and succeeded in the stabilization of the tetragonal structure phase at the room temperature [6][7][8][9][10][11][12][13][14][15][16][17][18][19]. However, the poor thermodynamic stability of these oxides in reducing atmospheres hinders their real applications and comprises the main task to be solved.…”