On {alpha}-{beta} phase transition in cristobalite-type Al{sub 1-} {sub x} Ga {sub x} PO{sub 4} (0.00{<=}x{<=}1.00)

Journal Article · Mon Jan 15 00:00:00 EST 2007 · Journal of Solid State Chemistry

DOI:https://doi.org/10.1016/j.jssc.2006.09.017· OSTI ID:21015622

Achary, S N ^[1]; Mishra, R ^[1]; Jayakumar, O D ^[1]; Kulshreshtha, S K ^[1]

---

1. Chemistry Division, Bhabha Atomic Research Centre, Mumbai-400 085 (India)

The results of variable temperature powder X-ray diffraction and differential thermal analysis (DTA) studies on the orthorhombic ({alpha}) low-cristobalite to cubic ({beta}) high-cristobalite phase transition for Al{sub 1-} {sub x} Ga {sub x} PO{sub 4}, (0.00{<=}x{<=}1.00) are presented. These studies reveal that all these compositions undergo reversible phase transitions from orthorhombic to cubic form at higher temperature. The high-temperature behavior of GaPO{sub 4} is observed to have a different behavior compared to all other compositions in this series. Orthorhombic low-cristobalite-type GaPO{sub 4} transforms to cubic high-cristobalite form at {approx}605 deg. C. Above {approx}700 deg. C, the cubic high-cristobalite-type GaPO{sub 4} slowly transforms to trigonal quartz type structure. At about 960 deg. C, the quartz type GaPO{sub 4} transforms back to the cubic high-cristobalite form. During cooling cycles the cubic phase of GaPO{sub 4} reverts to trigonal quartz type phase. However, annealing of GaPO{sub 4} at higher temperatures for longer duration can stabilize the orthorhombic low cristobalite phase. The phase transition temperatures and associated enthalpies are related to the change in unit cell volume and the orthorhombicity of the respective low cristobalite lattice. - Graphical abstract: The cristobalite-type GaPO{sub 4} relaxed slowly to quartz type modification above 700 deg. C (as indicated by a broad exotherm in inset)

• OSTI ID: 21015622
• Journal Information: Journal of Solid State Chemistry, Vol. 180, Issue 1; Other Information: DOI: 10.1016/j.jssc.2006.09.017; PII: S0022-4596(06)00527-5; Copyright (c) 2006 Elsevier Science B.V., Amsterdam, The Netherlands, All rights reserved; Country of input: International Atomic Energy Agency (IAEA); ISSN 0022-4596
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC
ORGANIC
PHYSICAL AND ANALYTICAL CHEMISTRY
ALUMINIUM PHOSPHATES
ANNEALING
COOLING
CRISTOBALITE
DIFFERENTIAL THERMAL ANALYSIS
ENTHALPY
GALLIUM PHOSPHATES
ORTHORHOMBIC LATTICES
PHASE TRANSFORMATIONS
QUARTZ
TEMPERATURE RANGE 0400-1000 K
TEMPERATURE RANGE 1000-4000 K
TRANSITION TEMPERATURE
X-RAY DIFFRACTION